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Sample records for ge si compounds

  1. RBS-study of GexSi1-x Compounds Formed by Variable Dose Ge Implantation into Si Wafers

    Directory of Open Access Journals (Sweden)

    Ramírez A.

    2002-01-01

    Full Text Available Amorphous and relaxed epitaxial GeSi films are prepared by Ge-implantation into Si(111 wafers of both 60 keV and 200 keV energetic Ge+-ions with appropriate dose, followed by post-implantation thermal annealing, comprising a single final annealing at a temperature of 900 °C. The implantation dose was varied between 10(14 and 10(17 atoms cm-2. Rutherford backscattering (RBS and channeling analysis was applied in order to explore the formation of a single crystalline Si-Ge compound layer, both prior and after the thermal treatment. The depth and the thickness of the implanted layer, as well as their molar composition and crystalline quality was determined, and it was found that a single crystalline Si-Ge alloy layer was created, with both depth and mole fraction depending on the ion energy and the ion dose.

  2. Magneto-Caloric Effect of Gd5Si2Ge2Compounds under Different Processing Conditions

    Institute of Scientific and Technical Information of China (English)

    Zeng Hong; Yue Ming; Niu Peili; Zhang Jiuxing

    2004-01-01

    The magneto-caloric effect of Gd5 Si2Ge2 compounds produced by various techniques is investigated in terms of their magnetization behaviors in the magnetic field from 0 to 2.0 T.The studied materials include arc-melted, annealed and sintered alloys.The results demonstrate that the Gd5Si2Ge2 alloys obtained under different processing conditions possess distinct magneto-caloric effect due to their various microstructures.Proper annealing treatment can enhance the magneto-caloric effect of the alloy remarkably.While the sintered alloy bears relatively lower value of magnetic entropy change ( △ SM) than arc-melted one.The magnetic entropy change of the annealed Gd5 Si2Ge2 alloy arrives the arrives the maximum value of - △SM = 15.29 J· kg-1· K-1 for magnetic field change under 2.0 T in the present work.

  3. Theoretical Study of Pd11 Si6 Nanosheet Compounds Including Seven-Coordinated Si Species and Its Ge Analogues.

    Science.gov (United States)

    Chen, Yue; Sunada, Yusuke; Nagashima, Hideo; Sakaki, Shigeyoshi

    2016-01-18

    Nanosheet compounds Pd11 (SiiPr)2 (SiiPr2 )4 (CNtBu)10 (1) and Pd11 (SiiPr)2 (SiiPr2 )4 (CNMes)10 (2), containing two Pd7 (SiiPr)(SiiPr2 )2 (CNR)4 plates (R=tBu or Mes) connected with three common Pd atoms, were investigated with DFT method. All Pd atoms are somewhat positively charged and the electron density is accumulated between the Pd and Si atoms, indicating that a charge transfer (CT) occurs from the Pd to the Si atoms of the SiMe2 and SiMe groups. Negative regions of the Laplacian of the electron density were found between the Pd and Si atoms. A model of a seven-coordinated Si species, that is, Pd5 (Pd-SiMe), is predicted to be a stable pentagonal bipyramidal molecule. Five Pd atoms in the equatorial plane form bonding overlaps with two 3p orbitals of the Si atom. This is a new type of hypervalency. The Ge analogues have geometry and an electronic structure similar to those of the Si compounds. But their formation energies are smaller than those of the Si analogues. The use of the element Si is crucial to synthesize these nanoplate compounds.

  4. Effect of Si/Ge ratio on resistivity and thermopower in Gd{sub 5}Si{sub x}Ge{sub 4-x} magnetocaloric compounds

    Energy Technology Data Exchange (ETDEWEB)

    Raj Kumar, D.M. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Manivel Raja, M., E-mail: mraja@dmrl.drdo.i [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Prabahar, K.; Chandrasekaran, V. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Poddar, Asok; Ranganathan, R. [Saha Institute of Nuclear Physics, Kolkata 700064 (India); Suresh, K.G. [Indian Institute of Technology Bombay, Mumbai 400076 (India)

    2011-07-15

    The effect of Si/Ge ratio on resistivity and thermopower behavior has been investigated in the magnetocaloric ferromagnetic Gd{sub 5}Si{sub x}Ge{sub 4-x} compounds with x=1.7-2.3. Microstructural studies reveal the presence of Gd{sub 5}(Si,Ge){sub 4}-matrix phase (5:4-type) along with traces of secondary phases (5:5 or 5:3-type). The x=1.7 and 2.0 samples display the presence of a first order structural transition from orthorhombic to monoclinic phase followed by a magnetic transition of the monoclinic phase. The alloys with x=2.2 and 2.3 display only magnetic transitions of the orthorhombic phase. A low temperature feature apparent in the AC susceptibility and resistivity data below 100 K reflects an antiferromagnetic transition of secondary phase(s) present in these compounds. The resistivity behavior study correlates with microstructural studies. A large change in thermopower of -8 {mu}V/K was obtained at the magneto-structural transition for the x=2 compound. - Research highlights: Effect of Si/Ge ratio on microstructure, magneto-structural transitions, resistivity ({rho}) and thermopower S(T) behaviour has been investigated in Gd{sub 5}Si{sub x}Ge{sub 4-x} compounds with x=1.7, 2.0, 2.2 and 2.3. Microstructural studies reveal the presence of a Gd{sub 5}(Si,Ge){sub 4} -matrix phase (5:4-type) along with traces of secondary phases (5:5 or 5:3-type). The resistivity behaviour has shown good correlation with the microstructural studies. A large change in thermopower of -8{mu}V/K was obtained at the magneto-structural transition for the x=2 compound. The resistivity and change in thermopower values were high for the alloys with Si/Ge ratio {<=}1 compared to that of the alloys with Si/Ge ratio >1.

  5. A Comparative Study of the Electronic and Magnetic Properties of Gd5Ge4 and Gd5Si4 Compounds

    Science.gov (United States)

    Z. Momeni, Larimi; Amirabadizadeh, A.; Yazdani, A.; Arabi, H.

    2014-12-01

    We present a comparative study of electronic structure and magnetic properties of Gd5Si4 and Gd5Ge4 compounds using first principles full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) using the WIEN2k code. The local-spin density approximation with correlation energy (LSDA+U) method has been used as the exchange-correlation potential. The optimized lattice constants are in good agreement with the experimental data. The total and partial density of states (DOS) of Gd5Si4 and Gd5Ge4 show the difference in Si 3p-Gd 5d and Ge 4p-Gd 5d hybridization, which have an effective role in indirect exchange interaction. In addition, the magnetic moments of Gd, Si, and Ge atoms and the compounds are calculated to clarify the differences in the magnetic properties of these compounds.

  6. Synthesis and fundamental properties of stable Ph(3)SnSiH(3) and Ph(3)SnGeH(3) hydrides: model compounds for the design of Si-Ge-Sn photonic alloys.

    Science.gov (United States)

    Tice, Jesse B; Chizmeshya, Andrew V G; Groy, Thomas L; Kouvetakis, John

    2009-07-06

    The compounds Ph(3)SnSiH(3) and Ph(3)SnGeH(3) (Ph = C(6)H(5)) have been synthesized as colorless solids containing Sn-MH(3) (M = Si, Ge) moieties that are stable in air despite the presence of multiple and highly reactive Si-H and Ge-H bonds. These molecules are of interest since they represent potential model compounds for the design of new classes of IR semiconductors in the Si-Ge-Sn system. Their unexpected stability and high solubility also makes them a safe, convenient, and potentially useful delivery source of -SiH(3) and -GeH(3) ligands in molecular synthesis. The structure and composition of both compounds has been determined by chemical analysis and a range of spectroscopic methods including multinuclear NMR. Single crystal X-ray structures were determined and indicated that both compounds condense in a Z = 2 triclinic (P1) space group with lattice parameters (a = 9.7754(4) A, b = 9.8008(4) A, c = 10.4093(5) A, alpha = 73.35(10)(o), beta = 65.39(10)(o), gamma = 73.18(10)(o)) for Ph(3)SnSiH(3) and (a = 9.7927(2) A, b = 9.8005(2) A, c = 10.4224(2) A, alpha = 74.01(3)(o), beta = 65.48(3)(o), gamma = 73.43(3)(o)) for Ph(3)SnGeH(3). First principles density functional theory simulations are used to corroborate the molecular structures of Ph(3)SnSiH(3) and Ph(3)SnGeH(3), gain valuable insight into the relative stability of the two compounds, and provide correlations between the Si-Sn and Ge-Sn bonds in the molecules and those in tetrahedral Si-Ge-Sn solids.

  7. Half-metallicity and magnetism of quaternary Heusler compounds CoRuTiZ (Z=Si, Ge, and Sn)

    Science.gov (United States)

    Bahramian, S.; Ahmadian, F.

    2017-02-01

    First-principle calculations based on the density functional theory for new quaternary Heusler compounds CoRuTiZ (Z=Si, Ge, and Sn) were performed. It was found that all three compounds were stable at YI structure in ferromagnetic state. The CoRuTiSi, CoRuTiGe, and CoRuTiSn were half-metal with integer magnetic moments of 1.00 μB per formula unit and half-metallic gaps of 0.13, 0.10, and 0.01 eV at their equilibrium volume, respectively. The density of states (DOSs) and band structures of these compounds were studied and the origin of half-metallicity was discussed. The CoRuTiSi, CoRuTiGe, and CoRuTiSn compounds showed half-metallic characteristics at lattice constants ranges of 5.77-6.36 Å, 5.66-6.16 Å, and 5.83-6.23 Å, indicating the lattice distortion did not affect the half-metallic properties of these compounds which makes them interesting materials in the spintronic field.

  8. Magnetic ordering of Hf3Ni2Si3-type {Sm, Tb, Er}3Co2Ge3 and {Tb, Ho}3Ni2Ge3 compounds

    Science.gov (United States)

    Morozkin, A. V.; Yapaskurt, V. O.; Nirmala, R.; Quezado, S.; Malik, S. K.; Mozharivskyj, Y.; Isnard, O.

    2017-02-01

    The magnetic ordering of Hf3Ni2Si3-type {Sm, Tb, Er}3Co2Ge3 and {Tb, Ho}3Ni2Ge3 compounds (space group Cmcm, oC32) was investigated via magnetization measurements and neutron diffraction study in a zero-applied field. {Sm, Tb, Er}3Co2Ge3 and Ho3Ni2Ge3 exhibit field sensitive complex antiferromagnetic orderings with TN=51 K, Tm=10 K for Sm3Co2Ge3, TN=34 K, Tm=13 K for Tb3Co2Ge3, TN=7 K for Er3Co2Ge3 and TN=11 K for Ho3Ni2Ge3. At 2 K and above the critical field of 5 kOe, 20 kOe, 4 kOe and 7 kOe for Sm3Co2Ge3, Tb3Co2Ge3, Er3Co2Ge3 and Ho3Ni2Ge3, respectively, saturation magnetizations per rare-earth atom are 6.5 μB for Tb3Co2Ge3, 7.0 μB for Er3Co2Ge3 and 8.0 μB for Ho3Ni2Ge3 in the field of 140 kOe, whereas magnetization of Sm3Co2Ge3 has an antiferromagnetic behaviour. The isothermal magnetic entropy change, ΔSm, indicates a field-induced ferromagnetic ordering in Sm3Co2Ge3, Tb3Co2Ge3, Er3Co2Ge3 and Ho3Ni2Ge3 with a maximal ΔSm value of -10.9 J/kg K for Ho3Ni2Ge3 at 11 K for a field change of 50 kOe. In a zero-applied magnetic field, below TN=33 K and down to TmND=15 K Tb3Ni2Ge3 shows an ac-antiferromagnetic ordering with the C2‧/c magnetic space group, a K0=[0, 0, 0] propagation vector and a aTb3Ni2Ge3×bTb3Ni2Ge3×cTb3Ni2Ge3 magnetic unit cell. Below TmND=15 K, its magnetic structure is a sum of the ac-antiferromagnetic component with the C2‧/c magnetic space group of the K0 vector and a sine-modulated a-antiferromagnetic component of the K1=[0, 0, ±1/3] propagation vector (the magnetic unit cell is aTb3Ni2Ge3×bTb3Ni2Ge3×3cTb3Ni2Ge3). The magnetic structure is made from the 'Tb2 - 2Tb1‧ clusters of the Tb1 8f and Tb2 4c sublattices with a dominant role of the Tb2 sublattices in the magnetic ordering of Tb3Ni2Ge3.

  9. Phase transitions and magnetocaloric effects in intermetallic compounds MnFeX (X=P, As, Si, Ge)

    Institute of Scientific and Technical Information of China (English)

    O.Tegus; Bao Li-Hong; Song Lin

    2013-01-01

    Since the discovery of giant magnetocaloric effect in MnFeP1-xAsx compounds,much valuable work has been performed to develop and improve Fe2P-type transition-metal-based magnetic refrigerants.In this article,the recent progress of our studies on fundamental aspects of theoretical considerations and experimental techniques,effects of atomic substitution on the magnetism and magnetocalorics of Fe2P-type intermetallic compounds MnFeX (X=P,As,Ge,Si) is reviewed.Substituting Si (or Ge) for As leads to an As-free new magnetic material MnFeP1-xSi(Ge)x.These new materials show large magnetocaloric effects resembling MnFe(P,As) near room temperature.Some new physical phenomena,such as huge thermal hysteresis and 'virgin' effect,were found in new materials.On the basis of Landau theory,a theoretical model was developed for studying the mechanism of phase transition in these materials.Our studies reveal that MnFe(P,Si) compound is a very promising material for room-temperature magnetic refrigeration and thermo-magnetic power generation.

  10. Magnetocaloric and barocaloric effects in a Gd5Si2Ge2 compound

    Institute of Scientific and Technical Information of China (English)

    Zou Jun-Ding

    2012-01-01

    The first-order phase transition in Gd5Si2Ge2 is sensitive to both magnetic field and pressure.It may indicate that the influences of the magnetic field and the pressure on the phase transition are virtually equivalent.Moreover,theoretical analyses reveal that the total entropy change is almost definite at a certain Curie temperature no matter whether the applied external field is a magnetic field or a pressure. The entropy change curve can be broadened dramatically under pressure,and the refrigerant capacity is improved from 284.7 J/kg to 447.0 J/kg.

  11. Magnetic entropy change and large refrigerant capacity of Ce6Ni2Si3-type GdCoSiGe compound

    Institute of Scientific and Technical Information of China (English)

    Shen Jun; Zhang Hu; Wu Jian-Feng

    2011-01-01

    Magnetic entropy change (△Sm) and refrigerant capacity (RC) of Ce6Ni2Si3-type Gd6Co1.67Si2.5Ge0.5 compounds have been investigated. The Gd6Co1.67Si2.5Ge0.5 undergoes a reversible second-order phase transition at the Curie temperature TC = 296 K. The high saturation magnetization leads to a large △Sm and the maximal value of △Sm is found to be 5.9 J/kg ? K around TC for a field change of 0-5 T. A broad distribution of the △Sm peak is observed and the full width at half maximum of the △Sm peak is about 101 K under a magnetic field of 5 T. The large RC is found around TC and its value is 424 J/kg.

  12. Magnetocaloric properties of the Gd_5Si_(2.05-x)Ge_(1.95-x)Mn_(2x) compounds

    Institute of Scientific and Technical Information of China (English)

    E.Yüzüak; I.Dincer; Y.Elerman

    2010-01-01

    The influence of the manganese-alloying on the structure and magnetocaloric properties of the Gd5Si2.05Ge1.95 compound was studied by X-ray powder diffraction and magnetization measurements.The Gd5Si2.05-xGe1.95-xMn2x(2x=0,0.03 and 0.08) compounds crystallized in the Gd5Si2Ge2-type monoclinic structure.In all X-ray powder diffraction patterns,a minor hexagonal Gd5Si3 phase was observed as a second phase.With increasing Mn content,the unit cell volume increased.For the compounds with x=0,0.03 and 0.08,the fi...

  13. Electronic and magnetic properties of Mn-doped BeSiAs{sub 2} and BeGeAs{sub 2} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Krivosheeva, A V; Shaposhnikov, V L; Borisenko, V E [Belarusian State University of Informatics and Radioelectronics, P. Browka 6, 220013 Minsk (Belarus); Arnaud D' Avitaya, F; Lazzari, J-L [Centre Interdisciplinaire de Nanoscience de Marseille CINAM, UPR CNRS 3118 conventionnee a Aix-Marseille Universite, Case 913, Campus de Luminy, 13288 Marseille cedex 9 (France)], E-mail: anna@nano.bsuir.edu.by

    2009-01-28

    The structural, electronic and magnetic properties of BeSiAs{sub 2} and BeGeAs{sub 2} chalcopyrite ternary compounds doped with manganese were investigated by means of ab initio calculations. It was found that substitution of Be atoms by Mn increases the lattice constants of both compounds that provide acceptable mismatch with conventional Si, Ge and GaAs substrates. In spite of the increase of the spin polarization upon doping, both compounds possess antiferromagnetic (AFM) ordering with the impurity in the group II position whereas ferromagnetic (FM) ordering is obtained in the case of an impurity in the group IV position.

  14. Si/SiGe MMIC's

    Science.gov (United States)

    Luy, Johann-Friedrich; Strohm, Karl M.; Sasse, Hans-Eckard; Schueppen, Andreas; Buechler, Josef; Wollitzer, Michael; Gruhle, Andreas; Schaeffler, Friedrich; Guettich, Ulrich; Klaassen, Andreas

    1995-04-01

    Silicon-based millimeter-wave integrated circuits (SIMMWIC's) can provide new solutions for near range sensor and communication applications in the frequency range above 50 GHz. This paper gives a survey on the state-of-the-art performance of this technology and on first applications. The key devices are IMPATT diodes for mm-wave power generation and detection in the self-oscillating mixer mode, p-i-n diodes for use in switches and phase shifters, and Schottky diodes in detector and mixer circuits. The silicon/silicon germanium heterobipolar transistor (SiGe HBT) with f(sub max) values of more than 90 GHz is now used for low-noise oscillators at Ka-band frequencies. First system applications are discussed.

  15. Giant magnetoresistance in the Ge-rich magnetocaloric compound, Gd{sub 5}(Si{sub 0.1}Ge{sub 0.9}){sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Morellon, L. E-mail: morellon@posta.unizar.es; Algarabel, P.A.; Magen, C.; Ibarra, M.R

    2001-12-01

    We have measured the zero-field electrical resistivity in the temperature range 5-295 K and magnetoresistance in magnetic fields of up to 12 T of Gd{sub 5}(Si{sub 0.1}Ge{sub 0.9}){sub 4}. The resistivity changes drastically at the magnetostructural first-order transition (T{sub C} congruent with 80 K on heating). This transition can be induced reversibly by the application of an external magnetic field above T{sub C}, producing a concomitant giant magnetoresistance (GMR) effect, {delta}{rho}/{rho} congruent with -50%. This study demonstrates that (in addition to giant magnetocaloric and magnetoelastic effects) GMR can be tuned between {approx}20 and {approx}290 K in Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} with x{<=}0.5 by simply adjusting the Si : Ge ratio.

  16. Influence of 1523 K annealing on phase and magnetic properties in (Gd1−Er)5Si2Ge2 compounds

    Indian Academy of Sciences (India)

    Xiang Chen; Yungui Chen; Yangbo Tang

    2011-08-01

    The (Gd1−Er)5Si2Ge2 ( = 0, 0.05, 0.1, 0.15 and 0.2) compounds were prepared from the high purity Gd metal (3 N) by arc melting, and then annealed at 1523 K (3 h). The phase, microstructure, Curie temperatures, magnetic hysteresis loss, and magnetocaloric effects were investigated. All samples retain the monoclinic Gd5Si2Ge2 type structure. The temperature of magnetic transition decreases linearly from 281 K to 177 K with the increase of Er content from = 0–0.2. Because the (Gd1−Er)5Si2Ge2 compounds keep the typical first-order structural/magnetic transition, they display large magnetic entropy near their magnetic transition temperatures. The maximum magnetic entropy change of (Gd1−Er)Si2Ge2 compounds in the low magnetic field of 0∼2.0 T are 15.5, 16.1, 15.3 and 15.2 J/kg K for = 0.05, 0.1, 0.15 and 0.2, respectively.

  17. Magnetic properties of the compounds ThCO{sub 2}Ge{sub 2} and ThCo{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kuznietz, Moshe [Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577 (Japan); Yamamura, Tomoo [Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577 (Japan)], E-mail: yamamura@imr.tohoku.ac.jp; Li Dexin; Shiokawa, Yoshinobu [Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577 (Japan)

    2008-10-15

    Rather old preparation of the compounds ThCo{sub 2}Ge{sub 2} and ThCo{sub 2}Si{sub 2} and their magnetic study in the temperature range 100-570 K, published by Omejec and Ban [Z. Anorg. Allg. Chem. 380 (1971) 111], indicated that both compounds ordered ferrromagnetically below 100 K. In order to verify the old data, polycrystalline samples of ThCo{sub 2}Ge{sub 2} and ThCo{sub 2}Si{sub 2} have been prepared by arc melting and subsequent annealing, and studied by X-ray diffraction at room temperature (RT), by superconducting quantum interference device (SQUID)-magnetization and AC-susceptibility measurements at 2-320 K, and by dc-magnetization measurements in variable magnetic fields up to 120 kOe at 5, 80, and 283 K. The magnetic measurements confirm the ferromagnetic ordering in both compounds, but with totally different Curie temperatures: {approx}120(20) K for ThCo{sub 2}Ge{sub 2} and above 320 K for ThCo{sub 2}Si{sub 2}. The paramagnetic values of ThCo{sub 2}Ge{sub 2} and the ordering of both compounds are discussed and compared with the old results of Omejec and Ban.

  18. Ge-on-Si optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Liu Jifeng, E-mail: Jifeng.Liu@Dartmouth.edu [Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 (United States); Camacho-Aguilera, Rodolfo; Bessette, Jonathan T.; Sun, Xiaochen [Microphotonics Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wang Xiaoxin [Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 (United States); Cai Yan; Kimerling, Lionel C.; Michel, Jurgen [Microphotonics Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2012-02-01

    Electronic-photonic synergy has become an increasingly clear solution to enhance the bandwidth and improve the energy efficiency of information systems. Monolithic integration of optoelectronic devices is the ideal solution for large-scale electronic-photonic synergy. Due to its pseudo-direct gap behavior in optoelectronic properties and compatibility with Si electronics, epitaxial Ge-on-Si has become an attractive solution for monolithic optoelectronics. In this paper we will review recent progress in Ge-on-Si optoelectronics, including photodetectors, electroabsorption modulators, and lasers. The performance of these devices has been enhanced by band-engineering such as tensile strain and n-type doping, which transforms Ge towards a direct gap material. Selective growth reduces defect density and facilitates monolithic integration at the same time. Ge-on-Si photodetectors have approached or exceeded the performance of their III-V counterparts, with bandwidth-efficiency product > 30 GHz for p-i-n photodiodes and bandwidth-gain product > 340 GHz for avalanche photodiodes. Enhanced Franz-Keldysh effect in tensile-strained Ge offers ultralow energy photonic modulation with < 30 fJ/bit energy consumption and > 100 GHz intrinsic bandwidth. Room temperature optically-pumped lasing as well as electroluminescence has also been achieved from the direct gap transition of band-engineered Ge-on-Si waveguides. These results indicate that band-engineered Ge-on-Si is promising to achieve monolithic active optoelectronic devices on a Si platform.

  19. Phase control studies in Gd{sub 5}Si{sub 2}Ge{sub 2} giant magnetocaloric compound

    Energy Technology Data Exchange (ETDEWEB)

    Belo, J.H. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Pereira, A.M., E-mail: ampereira@fc.up.pt [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Ventura, J.; Oliveira, G.N.P. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Araujo, J.P., E-mail: jearaujo@fc.up.pt [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Tavares, P.B.; Fernandes, L. [Departamento de Quimica and CQ-VR, Universidade de Tras-os-Montes e Alto Douro, 5001-801 Vila Real (Portugal); Algarabel, P.A. [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones Cientificas, 50009 Zaragoza (Spain); Magen, C. [Instituto de Nanociencia de Aragon-ARAID, Universidad de Zaragoza, 50009 Zaragoza (Spain); Morellon, L. [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones Cientificas, 50009 Zaragoza (Spain); Instituto de Nanociencia de Aragon, Universidad de Zaragoza, 50009 Zaragoza (Spain); and others

    2012-07-15

    Highlights: Black-Right-Pointing-Pointer Study of time dependence of O(I) to M phase. Black-Right-Pointing-Pointer Determination of the optimal annealing time. Black-Right-Pointing-Pointer New method for phase amount estimation (O(I) and M). Black-Right-Pointing-Pointer Effect of annealing on the MCE. Black-Right-Pointing-Pointer Analysis of the nature of the magnetic transition through the Arrot plot representation. - Abstract: A systematic set of annealings on arc-melted synthesized Gd{sub 5}Si{sub 2}Ge{sub 2} sample was performed. Through powder X-ray diffraction (XRD) and magnetometry measurements we monitored the effect of varying the annealing time with constant temperature (T = 1473 K) on the formation of the monoclinic (M) crystallographic phase fraction, which is the one responsible for the giant magnetocaloric effect (GMCE) in this compound. The conversion of the orthorhombic O(I) crystallographic phase into M was achieved, resulting in a significant increase of the M mass fraction. Such conversion led to a change in the magnetic transition nature, evolving from a second to a first order transition for the as-cast and annealed samples, respectively. An optimal annealing time range for the M phase conversion was identified to be within 80-120 min at T = 1473 K followed by a rapid quenching to liquid N{sub 2}. Furthermore, an increase up to {approx}50% of the magnetocaloric effect was obtained for the sample annealed during 120 min.

  20. First-principles study on the structural, electronic and magnetic properties of the Ti{sub 2}VZ (Z = Si, Ge, Sn) full-Heusler compounds

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Santao; Shen, Jiang [Institute for Applied Physics, University of Science and Technology Beijing, Beijing 100083 (China); Zhang, Chuan-Hui, E-mail: zhangch@ustb.edu.cn [National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-08-15

    In the present work, we have investigated the structural, electronic and magnetic properties of Ti{sub 2}VZ (Z = Si, Ge, Sn) alloys with Hg{sub 2}CuTi-type structure in the framework of density functional theory with generalized gradient approximation (GGA). The calculated results show that Ti{sub 2}VSi and Ti{sub 2}VGe alloys belong to half-metallic compounds with a perfect 100% spin polarization at the Fermi level while Ti{sub 2}VSn alloy is just a conventional ferrimagnetism compound. And the total magnetic moment of Ti{sub 2}VSi and Ti{sub 2}VGe obey the Slater–Pauling (SP) rule. In a moderate variation range of lattice distortion, Ti{sub 2}VSi and Ti{sub 2}VGe remain half-metallicity. We expect that our calculated results may trigger Ti{sub 2}VZ (Z = Si, Ge, Sn) applying in the future spintronics field. - Highlights: • Structural properties of Ti{sub 2}VZ (Z = Si, Ge, Sn) have been achieved by ab initio. • The calculations proved Ti{sub 2}VSi and Ti{sub 2}VGe to be half-metallic compounds. • The total magnetic moments of Ti{sub 2}VSi and Ti{sub 2}VGe followed the SP rule M{sub t} = Z{sub t} − 18. • Their magnetic and half-metallic properties changed with lattice distortion.

  1. Elasticity, Hardness and Thermal Conductivity of Si-Ge-Based Oxynitrides (SiGeN2O)

    Science.gov (United States)

    Ding, Yingchun; Chen, Min; Wu, Wenjuan; Xu, Ming

    2017-01-01

    Capitalizing on density functional theory, the novel Si-Ge-based oxynitrides (SiGeN2O) have been studied in terms of mechanical and thermal properties. Regarding α- or β-SiGeN2O, the SiGeN2O exhibits smaller mechanical moduli, suggesting a compressible and soft material. Our calculated lattice constants of two SiGeN2O phases are very consistent with other values. In addition, the hardness for SiGeN2O is investigated in details according to different semi-empirical methods. The results indicate a small hardness of two phases of SiGeN2O. Furthermore, the mechanical anisotropy, Debye temperature and the minimum thermal conductivity of two SiGeN2O compounds are clearly estimated for both SiGeN2O compounds. It is found that the SiGeN2O compounds show low thermal conductivity, which is suitable to be used as a thermal barrier coating.

  2. Elasticity, Hardness and Thermal Conductivity of Si-Ge-Based Oxynitrides (SiGeN2O)

    Science.gov (United States)

    Ding, Yingchun; Chen, Min; Wu, Wenjuan; Xu, Ming

    2016-09-01

    Capitalizing on density functional theory, the novel Si-Ge-based oxynitrides (SiGeN2O) have been studied in terms of mechanical and thermal properties. Regarding α- or β-SiGeN2O, the SiGeN2O exhibits smaller mechanical moduli, suggesting a compressible and soft material. Our calculated lattice constants of two SiGeN2O phases are very consistent with other values. In addition, the hardness for SiGeN2O is investigated in details according to different semi-empirical methods. The results indicate a small hardness of two phases of SiGeN2O. Furthermore, the mechanical anisotropy, Debye temperature and the minimum thermal conductivity of two SiGeN2O compounds are clearly estimated for both SiGeN2O compounds. It is found that the SiGeN2O compounds show low thermal conductivity, which is suitable to be used as a thermal barrier coating.

  3. The lower-valence coexisting ferrimagnetic Cr{sub 2}VX (X = Ga, Si, Ge, Sb) Heusler compounds: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Li Jia [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China)], E-mail: jiali@mail.hebut.edu.cn; Chen Guifeng; Li Jianfeng [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Li Yangxian [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China)], E-mail: admat@jsmail.hebut.edu.cn; Sun, Chang Q. [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2008-11-15

    First-principles investigation of the Heusler compounds Cr{sub 2}VX (X = Ga, Si, Ge, Sb) revealed that the Cr{sub 2}VSb exhibits a half-metallic nature yet Cr{sub 2}VSi and Cr{sub 2}VGe show nearly half-metallic ferromagnetism. Their band structures show a striking difference between the majority and minority spin directions. The Cr-V covalence bonding strength increases in the Ga {yields} Si {yields} Sb direction, with the d-d and p-d gaps developing gradually. The V atom shows a larger moment, of around 2.0 {mu}{sub B}, than previously reported values.

  4. Electronic structure and magnetism of new scandium-based full Heusler compounds: Sc{sub 2}CoZ (Z = Si, Ge, Sn)

    Energy Technology Data Exchange (ETDEWEB)

    Birsan, A., E-mail: anca_birsan@infim.ro

    2014-06-15

    Highlights: • First principles calculations were performed for Sc{sub 2}CoSi, Sc{sub 2}CoGe and Sc{sub 2}CoSn. • The total magnetic moments are 1μ{sub B}/f.u. at equilibrium lattice constants. • Sc{sub 2}CoSi is fully spin polarized for lattice parameters ranging between 6.21 and 6.56 Å. • Sc{sub 2}CoGe presents a pseudogap formed around Fermi level. • Sc{sub 2}CoSn exhibits a half metallic ferromagnetic character, up to 7.05 Å. - Abstract: First principles FPLAPW calculations were performed in the framework of Density Functional Theory (DFT), to study the electronic structures and magnetic properties for the new full-Heusler compounds: Sc{sub 2}CoZ (Z = Si, Ge, Sn). The investigated materials are stable against decomposition, in ferromagnetic configuration and crystallize in the inverse Heusler structures. The half-metallic properties as function of the variation of unit cell volumes are analysed regarding the fourth main group constituent elements. The electronic structure calculations for Sc{sub 2}CoSi and Sc{sub 2}CoSn show half-metallic characters, with indirect band gaps of 0.544 eV and 0.408 eV at optimised lattice parameters of 6.28 Å and 6.62 Å, respectively. For Sc{sub 2}CoGe compound, the Fermi energy is not pinned inside the energy band gap from minority density of states, neither for unit cell contraction nor for enlargement. The calculated total magnetic moments are 1μ{sub B}/f.u., for all compounds, in agreement with Slater–Pauling rule.

  5. Fabrication and ferromagnetism of Si-SiGe/MnGe core-shell nanopillars

    Science.gov (United States)

    Wang, Liming; Liu, Tao; Wang, Shuguang; Zhong, Zhenyang; Jia, Quanjie; Jiang, Zuimin

    2016-10-01

    Si-Si0.5Ge0.5/Mn0.08Ge0.92 core-shell nanopillar samples were fabricated on ordered Si nanopillar patterned substrates by molecular beam epitaxy at low temperatures. The magnetic properties of the samples are found to depend heavily on the growth temperature of the MnGe layer. The sample grown at a moderate temperature of 300 °C has the highest Curie temperature of 240 K as well as the strongest ferromagnetic signals. On the basis of the microstructural results, the ferromagnetic properties of the samples are believed to come from the intrinsic Mn-doped amorphous or crystalline Ge ferromagnetic phase rather than any intermetallic ferromagnetic compounds of Mn and Ge. After being annealed at a temperature of 500 °C, all the samples exhibit the same Curie temperature of 220 K, which is in sharp contrast to the different Curie temperature for the as-grown samples, and the ferromagnetism for the annealed samples comes from Mn5GeSi2 compounds which are formed during the annealing.

  6. Magnetic properties of R{sub 3}Cu{sub 4}X{sub 4} (R = Tb-Er; X = Si, Ge, Sn) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Szytula, A. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Cracow (Poland)]. E-mail: szytula@if.uj.edu.pl; Wawrzynska, E. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Cracow (Poland); Zarzycki, A. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Cracow (Poland)

    2007-09-13

    dc magnetization and magnetic susceptibility measurements were performed on polycrystalline samples of R{sub 3}Cu{sub 4}X{sub 4} (R = Tb-Er; T = Si, Ge, Sn) intermetallics which crystallize in the orthorhombic crystal structure of the Gd{sub 3}Cu{sub 4}Ge{sub 4}-type. All of the studied compounds are antiferromagnets showing complex behavior. For some of them additional transitions below Neel temperature are observed and few indicate metamagnetic transition at 2 K. Reciprocal magnetic susceptibilities of all the samples obey the Curie-Weiss law above the Neel temperatures with negative values of paramagnetic Curie temperatures and the effective magnetic moments of rare earth ions being close to the respective free R{sup 3+} ion values.

  7. GeSn/Ge multiquantum well photodetectors on Si substrates.

    Science.gov (United States)

    Oehme, M; Widmann, D; Kostecki, K; Zaumseil, P; Schwartz, B; Gollhofer, M; Koerner, R; Bechler, S; Kittler, M; Kasper, E; Schulze, J

    2014-08-15

    Vertical incidence GeSn/Ge multiquantum well (MQW) pin photodetectors on Si substrates were fabricated with a Sn concentration of 7%. The epitaxial structure was grown with a special low temperature molecular beam epitaxy process. The Ge barrier in the GeSn/Ge MQW was kept constant at 10 nm. The well width was varied between 6 and 12 nm. The GeSn/Ge MQW structures were grown pseudomorphically with the in-plane lattice constant of the Ge virtual substrate. The absorption edge shifts to longer wavelengths with thicker QWs in agreement with expectations from smaller quantization energies for the thicker QWs.

  8. Metastable Ge nanocrystalline in SiGe matrix for photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Ouyang, Yao-Tsung; Su, Chien-Hao [Department of Chemical and Materials Engineering, National Central University, Taoyuan City 320, Taiwan (China); Chang, Jenq-Yang [Department of Optics and Photonics, National Central University, Taoyuan City 320, Taiwan (China); Cheng, Shao-Liang; Lin, Po-Chen [Department of Chemical and Materials Engineering, National Central University, Taoyuan City 320, Taiwan (China); Wu, Albert T., E-mail: atwu@ncu.edu.tw [Department of Chemical and Materials Engineering, National Central University, Taoyuan City 320, Taiwan (China)

    2015-09-15

    Highlights: • Amorphous Si{sub 1−x}Ge{sub x} films were prepared by co-sputtering by using rapid thermal annealing to form nanocrystal films. • Si–Ge alloy does not form total solid solution that is shown in phase diagram. • HRTEM images indicated that Ge atoms segregated and formed Ge clusters that are embedded in the amorphous Si–Ge matrix. • Ge segregation permitted high mobility; the grain size increased and the resistivity decreased with higher Ge content. • The rectifying property became stronger with the Ge fraction in the Si{sub 1−x}Ge{sub x} diodes. Si{sub 1−x}Ge{sub x} diodes are used as photodetectors, which provide a greater output current under illumination. - Abstract: Amorphous Si{sub 1−x}Ge{sub x} films were prepared by co-sputtering on an oxidized Si wafer, followed by rapid thermal annealing to form nanocrystal films. The formation of Ge nanocrystals was not at thermodynamic equilibrium formed in the amorphous Si{sub 1−x}Ge{sub x} matrix. High-resolution transmission electron microscopy was used to characterize the increase in the size of the grains in the Ge nanocrystals as the Ge content increased. The Ge nanocrystals have a greater absorption in the near-infrared region and higher carrier mobility than SiGe crystals, and the variation in their grain sizes can be used to tune the bandgap. This characteristic was exploited herein to fabricate n-Si{sub 1−x}Ge{sub x}/p-Si{sub 1−x}Ge{sub x} p–n diodes on insulating substrates, which were then examined by analyzing their current–voltage characteristics. The rectifying property became stronger as the fraction of Ge in the Si{sub 1−x}Ge{sub x} films increased. The Si{sub 1−x}Ge{sub x} diodes are utilized as photodetectors that have a large output current under illumination. This paper elucidates the correlations between the structural, optical and electrical properties and the p–n junction performance of the film.

  9. Magnetoelastic phase transitions in the LuFe{sub 4}Ge{sub 2} and YFe{sub 4}Si{sub 2} compounds: A neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Schobinger-Papamantellos, P., E-mail: Schobinger@mat.ethz.ch [Laboratory of Crystallography, ETH-Zurich, 8093 Zuerich (Switzerland); Buschow, K.H.J., E-mail: buschow@gmail.com [Van der Waals-Zeeman Institute, University of Amsterdam, NL-1018 XE (Netherlands); Rodriguez-Carvajal, J. [Institut Laue-Langevin, 156X, 38042 Grenoble Cedex (France)

    2012-11-15

    The magnetic structure of the tetragonal antiferromagnetic LuFe{sub 4}Ge{sub 2} and YFe{sub 4}Si{sub 2} compounds has been studied by high resolution neutron and X-ray diffraction above and below the magneto-elastic transition at T{sub N}, T{sub c}=32 K and 76 K, respectively. Below T{sub N},T{sub c} the tetragonal high temperature (HT) phase transforms into the low temperature (LT) orthorhombic magnetic phase: P4{sub 2}/mnm (HT) {yields} Pnnm (q=0) (LT) with a 2D canted moment arrangement of the Fe moments within the (001) plane with the magnetic space group P(2{sub 1})/(n') (2{sub 1})/(n') (2{sub 1})/(m') (Sh{sub 58}{sup 399}). The Fe magnetic moment value is highly reduced in both compounds due to the presence of geometrical and exchange frustration relating to the underlying crystal structure comprising columns of Fe tetrahedra expanding along the c direction with antiferromagnetic interactions. The magnetic refinements were perturbed by the presence of partly unidentified impurity phases mainly in YFe{sub 4}Si{sub 2}. - Highlights: Black-Right-Pointing-Pointer Magnetic phase diagrams of LuFe{sub 4}Ge{sub 2} and YFe{sub 4}Si{sub 2} compounds studied by neutron and X-ray diffraction. Black-Right-Pointing-Pointer The HT tetragonal phases undergo magnetoelastic transitions below T{sub N,}T{sub C}=32 K and 76 K respectively. Black-Right-Pointing-Pointer Both phase diagrams comprise ranges of distinct symmetry: HT (P4{sub 2}/mnm), LT (Pnnm) orthorhombic. Black-Right-Pointing-Pointer The LT phases (Pnnm, q=0) correspond to planar canted Fe moment arrangements within the (001) plane. Black-Right-Pointing-Pointer The Fe moment values are highly reduced due to geometrical and exchange frustration.

  10. Relaxed SiGe-on-insulator fabricated by dry oxidation of sandwiched Si/SiGe/Si structure

    Energy Technology Data Exchange (ETDEWEB)

    Di Zengfeng [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Department of Physics and Material Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Zhang Miao [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Liu Weili [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Zhu Ming [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Department of Physics and Material Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Lin Chenglu [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Chu, Paul K. [Department of Physics and Material Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)]. E-mail: paul.chu@cityu.edu.hk

    2005-12-05

    An improved technique is demonstrated to fabricate silicon-germanium on insulator (SGOI) starting with a sandwiched structure of Si/SiGe/Si. After oxidation of the sandwiched structure and successive annealing, a relaxed SiGe-on-insulator (SGOI) structure is produced. Our results indicate that the added Si cap layer is advantageous in suppressing Ge loss at the initial stage of SiGe oxidation and the subsequent annealing process homogenizes the Ge fraction. Raman measurements reveal that the strain in the SiGe layer is fully relaxed at high oxidation temperature ({approx}1150 deg. C) without generating any threading dislocations and crosshatch patterns, which generally exist in the relaxed SiGe layer on bulk Si substrate.

  11. SiGe layer thickness effect on the structural and optical properties of well-organized SiGe/SiO2 multilayers

    Science.gov (United States)

    Vieira, E. M. F.; Toudert, J.; Rolo, A. G.; Parisini, A.; Leitão, J. P.; Correia, M. R.; Franco, N.; Alves, E.; Chahboun, A.; Martín-Sánchez, J.; Serna, R.; Gomes, M. J. M.

    2017-08-01

    In this work, we report on the production of regular (SiGe/SiO2)20 multilayer structures by conventional RF-magnetron sputtering, at 350 °C. Transmission electron microscopy, scanning transmission electron microscopy, raman spectroscopy, and x-ray reflectometry measurements revealed that annealing at a temperature of 1000 °C leads to the formation of SiGe nanocrystals between SiO2 thin layers with good multilayer stability. Reducing the nominal SiGe layer thickness (t SiGe) from 3.5-2 nm results in a transition from continuous SiGe crystalline layer (t SiGe ˜ 3.5 nm) to layers consisting of isolated nanocrystals (t SiGe ˜ 2 nm). Namely, in the latter case, the presence of SiGe nanocrystals ˜3-8 nm in size, is observed. Spectroscopic ellipsometry was applied to determine the evolution of the onset in the effective optical absorption, as well as the dielectric function, in SiGe multilayers as a function of the SiGe thickness. A clear blue-shift in the optical absorption is observed for t SiGe ˜ 2 nm multilayer, as a consequence of the presence of isolated nanocrystals. Furthermore, the observed near infrared values of n = 2.8 and k = 1.5 are lower than those of bulk SiGe compounds, suggesting the presence of electronic confinement effects in the nanocrystals. The low temperature (70 K) photoluminescence measurements performed on annealed SiGe/SiO2 nanostructures show an emission band located between 0.7-0.9 eV associated with the development of interface states between the formed nanocrystals and surrounding amorphous matrix.

  12. HV/CVD Grown Relaxed SiGe Buffer Layers for SiGe HMOSFETs

    Institute of Scientific and Technical Information of China (English)

    黄文韬; 罗广礼; 史进; 邓宁; 陈培毅; 钱佩信

    2003-01-01

    High-vacuum/chemical-vapor deposition (HV/CVD) system was used to grow relaxed SiGe buffer layers on Si substrates. Several methods were then used to analyze the quality of the SiGe films. X-ray diffraction and Raman spectroscopy showed that the upper layer was almost fully relaxed. Second ion mass spectroscopy showed that the Ge compositions were step-graded. Transmission electron microscopy showed that the misfit dislocations were restrained to the graded SiGe layers. Tests of the electrical properties of tensile-strained Si on relaxed SiGe buffer layers showed that their transconductances were higher than that of Si devices. These results verify the high quality of the relaxed SiGe buffer layer. The calculated critical layer thicknesses of the graded Si1-xGex layer on Si substrate and a Si layer on the relaxed SiGe buffer layer agree well with experimental results.

  13. Microstructure study of the rare-earth intermetallic compounds R5(SixGe1-x)4 and R5(SixGe1-x)3

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Qing [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    The unique combination of magnetic properties and structural transitions exhibited by many members of the R5(SixGe1-x)4 family (R = rare earths, 0 ≤ x ≤ 1) presents numerous opportunities for these materials in advanced energy transformation applications. Past research has proven that the crystal structure and magnetic ordering of the R5(SixGe1-x)4 compounds can be altered by temperature, magnetic field, pressure and the Si/Ge ratio. Results of this thesis study on the crystal structure of the Er5Si4 compound have for the first time shown that the application of mechanical forces (i.e. shear stress introduced during the mechanical grinding) can also result in a structural transition from Gd5Si4-type orthorhombic to Gd5Si2Ge2-type monoclinic. This structural transition is reversible, moving in the opposite direction when the material is subjected to low-temperature annealing at 500 °C.

  14. 与Si工艺兼容的Si/SiGe/Si HBT研究%The Study of Si/SiGe/Si HBT and Its Compatibility with Si Process

    Institute of Scientific and Technical Information of China (English)

    廖小平

    2001-01-01

    我们对Si/SiGe/Si HBT及其Si兼容工艺进行了研究,在研究了一些关键的单项工艺的基础上,提出了五个高速Si/SiGe/Si HBT结构和一个低噪声Si/SiGe/Si HBT结构,并已研制成功台面结构Si/SiGe/Si HBT和低噪声Si/SiGe/Si HBT,为进一步高指标的Si/SiGe/Si HBT的研究建立了基础.

  15. 射频 Si/SiGe/Si HBT的研究%Studies on RF Si/SiGe/Si HBT

    Institute of Scientific and Technical Information of China (English)

    廖小平; 殷刚毅

    2003-01-01

    Si/SiGe/Si HBT与Si工艺兼容的研究基础上,对射频Si/SiGe/Si HBT的射频特性和制备工艺进行了研究,分析了与器件结构有关的关键参数寄生电容和寄生电阻与Si/SiGe/Si HBT的特征频率fT和最高振荡频率fmax的关系,成功地制备了fT为2.5 GHz、fmax为2.3 GHz的射频Si/SiGe/Si HBT,为具有更好的射频性能的Si/SiGe/Si HBT的研究建立了基础.

  16. Phonons in Ge/Si superlattices with Ge quantum dots

    CERN Document Server

    Milekhin, A G; Pchelyakov, O P; Schulze, S; Zahn, D R T

    2001-01-01

    Ge/Si superlattices with Ge quantum dots obtained by means of molecular-beam epitaxy were investigated by means of light Raman scattering under resonance conditions. These structures are shown to have oscillation properties of both two-dimensional and zero-dimensional objects. Within spectrum low-frequency range one observes twisted acoustic phonons (up to 15 order) typical for planar superlattices. Lines of acoustic phonons are overlapped with a wide band of continuous emission. Analysis of frequencies of Ge and Ge-Si optical phonons shows that Ge quantum dots are pseudoamorphous ones and mixing of Ge and Si atoms is a negligible one. One detected low-frequency shift of longitudinal optical phonons at laser excitation energy increase (2.54-2.71 eV)

  17. Ge/SiGe superlattices for nanostructured thermoelectric modules

    Energy Technology Data Exchange (ETDEWEB)

    Chrastina, D., E-mail: daniel@chrastina.net [L-NESS Politecnico di Milano, Polo di Como, via Anzani 42, 22100 Como (Italy); Cecchi, S. [L-NESS Politecnico di Milano, Polo di Como, via Anzani 42, 22100 Como (Italy); Hague, J.P. [Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom); Frigerio, J. [L-NESS Politecnico di Milano, Polo di Como, via Anzani 42, 22100 Como (Italy); Samarelli, A.; Ferre–Llin, L.; Paul, D.J. [School of Engineering, University of Glasgow, Oakfield Avenue, Glasgow, G12 8LT (United Kingdom); Müller, E. [Electron Microscopy ETH Zurich (EMEZ), ETH-Zürich, CH-8093 (Switzerland); Etzelstorfer, T.; Stangl, J. [Institut für Halbleiter und Festkörperphysik, Universität Linz, A-4040 Linz (Austria); Isella, G. [L-NESS Politecnico di Milano, Polo di Como, via Anzani 42, 22100 Como (Italy)

    2013-09-30

    Thermoelectrics are presently used in a number of applications for both turning heat into electricity and also for using electricity to produce cooling. Mature Si/SiGe and Ge/SiGe heteroepitaxial growth technology would allow highly efficient thermoelectric materials to be engineered, which would be compatible and integrable with complementary metal oxide silicon micropower circuits used in autonomous systems. A high thermoelectric figure of merit requires that electrical conductivity be maintained while thermal conductivity is reduced; thermoelectric figures of merit can be improved with respect to bulk thermoelectric materials by fabricating low-dimensional structures which enhance the density of states near the Fermi level and through phonon scattering at heterointerfaces. We have grown and characterized Ge-rich Ge/SiGe/Si superlattices for nanofabricated thermoelectric generators. Low-energy plasma-enhanced chemical vapor deposition has been used to obtain nanoscale-heterostructured material which is several microns thick. Crystal quality and strain control have been investigated by means of high resolution X-ray diffraction. High-resolution transmission electron microscopy images confirm the material and interface quality. Electrical conductivity has been characterized by the mobility spectrum technique. - Highlights: ► High-quality Ge/SiGe multiple quantum wells for thermoelectric applications ► Mobility spectra of systems featuring a large number of parallel conduction channels ► Competitive thermoelectric properties measured in single devices.

  18. Magnetoelastic phase transitions in the LuFe4Ge2 and YFe4Si2 compounds: A neutron diffraction study

    Science.gov (United States)

    Schobinger-Papamantellos, P.; Buschow, K. H. J.; Rodríguez-Carvajal, J.

    2012-11-01

    The magnetic structure of the tetragonal antiferromagnetic LuFe4Ge2 and YFe4Si2 compounds has been studied by high resolution neutron and X-ray diffraction above and below the magneto-elastic transition at TN, Tc=32 K and 76 K, respectively. Below TN,Tc the tetragonal high temperature (HT) phase transforms into the low temperature (LT) orthorhombic magnetic phase: P42/mnm (HT) → Pnnm (q=0) (LT) with a 2D canted moment arrangement of the Fe moments within the (001) plane with the magnetic space group P{21}/{n'}{21}/{n'}{21}/{m'}(Sh58399). The Fe magnetic moment value is highly reduced in both compounds due to the presence of geometrical and exchange frustration relating to the underlying crystal structure comprising columns of Fe tetrahedra expanding along the c direction with antiferromagnetic interactions. The magnetic refinements were perturbed by the presence of partly unidentified impurity phases mainly in YFe4Si2.

  19. Phase stabilities of pyrite-related MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te): A systematic DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Bachhuber, Frederik [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany); School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland (New Zealand); Krach, Alexander; Furtner, Andrea [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany); Söhnel, Tilo [School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland (New Zealand); Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University Auckland, Auckland (New Zealand); Peter, Philipp; Rothballer, Jan [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany); Weihrich, Richard, E-mail: richard.weihrich@chemie.uni-r.de [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany)

    2015-03-15

    Pyrite-type and related systems appear for a wide range of binary and ternary combinations of transition metals and main group elements that form Zintl type dumbbell anion units. Those representatives with 20 valence electrons exhibit an extraordinary structural flexibility and interesting properties as low-gap semiconductors or thermoelectric and electrode materials. This work is devoted to the systematic exploration of novel compounds within the class of MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te) by means of density functional calculations. Their preferred structures are predicted from an extended scheme of colored pyrites and marcasites. To determine their stabilities, competing binary MT{sub 2} and MCh{sub 2} boundary phases are taken into account as well as ternary M{sub 3}T{sub 2}Ch{sub 2} and M{sub 2}T{sub 3}Ch{sub 3} systems. Recently established stability diagrams are presented to account for MTCh ordering phenomena with a focus on a not-yet-reported ordering variant of the NiAs{sub 2} type. Due to the good agreement with experimental data available for several PtTCh systems, the predictions for the residual systems are considered sufficiently accurate. - Graphical abstract: Compositional and structural stability of MTCh compounds is investigated from first principle calculations. A conceptional approach is presented to study and predict novel stable and metastable compounds and structures of low gap semiconductors with TCh dumbbell units that are isoelectronic and structurally related to pyrite (FeS{sub 2}). - Highlights: • Study of compositional stability of MTCh vs. M{sub 3}T{sub 2}Ch{sub 2} and M{sub 2}T{sub 3}Ch{sub 3} compounds. • Study of structural stability of known and novel MTCh compounds. • Prediction of novel stable and metastable structures and compounds isoelectronic to pyrite, FeS{sub 2}.

  20. Synthesis of Epitaxial Films Based on Ge-Si-Sn Materials with Ge/GeSn, Ge/GeSiSn, and GeSn/GeSiSn Heterojunctions

    Science.gov (United States)

    Timofeev, V. A.; Kokhanenko, A. P.; Nikiforov, A. I.; Mashanov, V. I.; Tuktamyshev, A. R.; Loshkarev, I. D.

    2015-11-01

    Results of investigations into the synthesis of heterostructures based on Ge-Si-Sn materials by the method of low-temperature molecular beam epitaxy are presented. The formation of epitaxial films during structure growth has been controlled by the reflection high-energy electron diffraction method. Films with Ge/GeSn, Ge/GeSiSn, and GeSn/GeSiSn heterojunctions are grown with Sn content changing from 2 to 10 % at temperatures in the interval 150-350°C. The stressed state, the composition, and the lattice parameter are studied by the x-ray diffraction method using Omega-scan curves and reciprocal space maps. A tensile strain in the Ge film during Ge/Ge0.9Sn0.1/Si structure growth has reached 0.86%.

  1. Ground state properties and thermoelectric behavior of Ru2VZ (Z=Si, ge, sn) half-metallic ferromagnetic full-Heusler compounds

    Science.gov (United States)

    Yalcin, Battal Gazi

    2016-06-01

    The ground state properties namely structural, mechanical, electronic and magnetic properties and thermoelectric behavior of Ru2VZ (Z=Si, Ge and Sn) half-metallic ferromagnetic full-Heusler compounds are systematically investigated. These compounds are ferromagnetic and crystallize in the Heusler type L21 structure (prototype: Cu2MnAl, Fm-3m 225). This result is confirmed for Ru2VSi and Ru2VSn by experimental work reported by Yin and Nash using high temperature direct reaction calorimetry. The studied materials are half-metallic ferromagnets with a narrow direct band gap in the minority spin channel that amounts to 31 meV, 66 meV and 14 meV for Ru2VSi, Ru2VGe, and Ru2VSn, respectively. The total spin magnetic moment (Mtot) of the considered compounds satisfies a Slater-Pauling type rule for localized magnetic moment systems (Mtot=(NV-24)μB), where NV=25 is the number of valence electrons in the primitive cell. The Curie temperature within the random phase approximation (RPA) is found to be 23 K, 126 K and 447 K for Ru2VSi, Ru2VGe and Ru2VSn, respectively. Semi-classical Boltzmann transport theories have been used to obtain thermoelectric constants, such as Seebeck coefficient (S), electrical (σ/τ) and thermal conductivity (κ/τ), power factor (PF) and the Pauli magnetic susceptibility (χ). ZTMAX values of 0.016 (350 K), 0.033 (380 K) and 0.063 (315 K) are achieved for Ru2VSi, Ru2VGe and Ru2VSn, respectively. It is expected that the obtained results might be a trigger in future experimentally interest in this type of full-Heusler compounds.

  2. Quantum devices using SiGe/Si heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Karunasiri, R.P.G.; Wang, K.L. (Univ. of California, Los Angeles (United States))

    Strained-layer Si{sub 1-x}Ge{sub x}/Si heterostructures have created a great deal of interest due to the potential of integration with the conventional silicon very large scale integrated technology. With the current advances in silicon molecular beam epitaxy (Si-MBE) and other low-temperature epitaxial techniques, many Si{sub 1-x}Ge{sub x}/Si heterojunction devices have been realized. For example, among those realized are avalanche photodiodes, modulation-doped field-effect transistors, heterojunction bipolar transistors, and more recently, resonant tunneling structures, hot-carrier transistors, and quantum well metal-oxide-semiconductor field-effect transistors. In this paper several quantum size effects in strained Si{sub 1-x}Ge{sub x} layers and their potential in device applications will be reviewed. Among those to be discussed are resonant tunneling, miniband transport, and intersubband absorption in Si{sub 1-x}Ge{sub x}/Si superlattice structures, optical properties of monolayer Si{sub m}Ge{sub n} superlattices, and observation of large Stark effect associated with interband transition between quantized states in Si{sub 1-x}Ge{sub x}/Si quantum well structures.

  3. Formation of extended defects in SiGe/Si heterostructures with SiGeC intermediate layers

    Energy Technology Data Exchange (ETDEWEB)

    Vdovin, V.I.; Reznik, V.Ya. [Institute for Chemical Problems of Microelectronics, Moscow (Russian Federation); Torack, T.A.; Fei, Lu [MEMC Inc, St Peters, MO (United States); Mil' vidskii, M.G. [Institute of Rare Metals ' Giredmet' , Moscow (Russian Federation); Falster, R. [MEMC Electronic Materials SpA, Novara (Italy)

    2007-07-01

    The generation of misfit dislocations (MDs) and stacking faults (SFs) was studied by TEM and preferential chemical etching in multilayer Si(001)/SiGe/SiGeC(10 nm)/SiGe/Si heterostructures grown by CVD at 650 C. Prior to growth of Si layer, the other part of heterostructure was annealed at 950 C in the growth chamber to get relaxed buffer layers and strained Si layer free of extended defects. We used SiGe alloys with Ge content of 24 at.% and C content of 0.5 at.%. Carbon in the strained SiGe matrix was found to promote high rates of strain relaxation through the nucleation of perfect dislocation loops close to the interface with Si substrate. For Si layer thickness >10 nm, threading dislocations split in these layers under tensile strain to form SFs. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. DESIGN AND FABRICATION OF Si/SiGe PMOSFETs

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on theoretical analysis and computer-aided simulation, optimized design prin-ciples for Si/SiGe PMOSFET are given in this paper, which include choice of gate materials, determination of germanium percentage and profile in SiGe channel, optimization of thickness of dioxide and silicon cap layer, and adjustment of threshold voltage.In the light of these principles, a SiGe PMOSFET is designed and fabricated successfully.Measurement indicates that the SiGe PMOSFET's(L=2μ同洒45 mS/mm(300K) and 92 mS/mm(77K) ,while that is 33mS/mm (300K) and 39mS/mm (77K) in Si PMOSFET with the same structure.

  5. DESIGN AND FABRICATION OF Si/SiGe PMOSFETs

    Institute of Scientific and Technical Information of China (English)

    Yang Peifeng; Zhang Jing; Yi Qiang; Fan Zerui; Li Jingchun; Yu Qi; Wang Xiangzhan; Yang Mohua; He Lin; Li Kaicheng; Tan Kaizhou; Liu Daoguang

    2002-01-01

    Based on theoretical analysis and computer-aided simulation, optimized design principles for Si/SiGe PMOSFET are given in this paper, which include choice of gate materials,determination of germanium percentage and profile in SiGe channel, optimization of thickness of dioxide and silicon cap layer, and adjustment of threshold voltage. In the light of these principles,a SiGe PMOSFET is designed and fabricated successfully. Measurement indicates that the SiGe PMOSFET's (L=2μm) transconductance is 45 mS/mm (300K) and 92mS/mm (77K), while that is 33 mS/mm (300K) and 39mS/mm (77K) in Si PMOSFET with the same structure.

  6. Electronic structure and magnetism of new ilmenite compounds for spintronic devices: FeBO{sub 3} (B = Ti, Hf, Zr, Si, Ge, Sn)

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, R.A.P. [Department of Chemistry, State University of Ponta Grossa, Av. General Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR (Brazil); Camilo, A. [Department of Physics, State University of Ponta Grossa, Av. General Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR (Brazil); Lazaro, S.R. de, E-mail: srlazaro@uepg.br [Department of Chemistry, State University of Ponta Grossa, Av. General Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR (Brazil)

    2015-11-15

    First-principles calculations were performed in the framework of Density Functional Theory (DFT) within hybrid functional (B3LYP) to study the electronic structure and magnetic properties of new ilmenite FeBO{sub 3} (B=Ti, Hf, Zr, Si, Ge, Sn) materials. In particular, the magnetic exchange interaction between Fe{sup 2+} layers is dependent on the interlayer distance and it can be controlled by ionic radius of B-site cation. Thus, Fe(Ti, Si, Ge)O{sub 3} are antiferromagnetic materials, while Fe(Zr, Hf, Sn)O{sub 3} are ferromagnetic. We also argue that antiferromagnetic materials and FeZrO{sub 3} are convectional semiconductors, whereas FeHfO{sub 3} and FeSnO{sub 3} exhibit intrinsic half-metallic behavior, making them promising candidates for spintronic devices. - Highlights: • We study electronic structure and magnetism of new FeBO{sub 3} (B=Ti, Hf, Zr, Si, Ge, Sn) ilmenite materials. • We found that magnetic ordering of Fe-based ilmenite materials can be controlled by size of B-site cation. • Fe(Ti, Zr, Si, Ge)O{sub 3} are convectional semiconductors. • FeHfO{sub 3} and FeSnO{sub 3} exhibit intrinsic half-metallic behavior with potential application for spintronic devices.

  7. Effect of rare earth ion in the thermopower of R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} compounds with x{approx}0.5 and R=Gd and Tb

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, A.M. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal)]. E-mail: ampereira@fc.up.pt; Magen, C. [Instituto de Ciencia de Materiales de Aragon Universidad de Zaragoza and Consejo Superior de Investigaciones Cient icas, 50009 Zaragoza (Spain); Araujo, J.P. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Algarabel, P.A. [Instituto de Ciencia de Materiales de Aragon Universidad de Zaragoza and Consejo Superior de Investigaciones Cient icas, 50009 Zaragoza (Spain); Morellon, L. [Instituto de Ciencia de Materiales de Aragon Universidad de Zaragoza and Consejo Superior de Investigaciones Cient icas, 50009 Zaragoza (Spain); Instituto de Nanociencia de Aragon, 50009 Zaragoza (Spain); Braga, M.E. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Pinto, R.P. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Ibarra, M.R. [Instituto de Ciencia de Materiales de Aragon Universidad de Zaragoza and Consejo Superior de Investigaciones Cient icas, 50009 Zaragoza (Spain); Instituto de Nanociencia de Aragon, 50009 Zaragoza (Spain); Sousa, J.B. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal)

    2007-03-15

    The magnetocaloric ferromagnetic compounds with R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} composition are very sensitive to the Si:Ge ratio (x) and the particular Rare earth (R) ion. Here we study the thermopower S(T) behavior of samples with a similar x{approx}0.5 ratio but different rare earth ions: Gd{sub 5}(Si{sub 0.45}Ge{sub 0.55}){sub 4} and Tb{sub 5}(Si{sub 0.5}Ge{sub 0.5}){sub 4}, between 10 and 290K. Above the Curie temperature (T{sub C}) both S and its T-dependence do not change with the R-ion but, upon cooling, a first-order magneto-structural transition occurs at T{sub S} (close to T{sub C}) causing an abruptness in thermopower ({delta}S/S{approx}32%). At low temperatures very distinct S(T) behavior is observed, and a spin reorientation transition occurs in the Tb compound.

  8. Strained Si/SiGe MOS transistor model

    Directory of Open Access Journals (Sweden)

    Tatjana Pešić-Brđanin

    2009-06-01

    Full Text Available In this paper we describe a new model of surfacechannel strained-Si/SiGe MOSFET based on the extension of non-quasi-static (NQS circuit model previously derived for bulk-Si devices. Basic equations of the NQS model have been modified to account for the new physical parameters of strained-Si and relaxed-SiGe layers. From the comparisons with measurements, it is shown that a modified NQS MOS including steady-state self heating can accurately predict DC characteristics of Strained Silicon MOSFETs.

  9. Thermopower and electrical resistivity behavior near the martensitic transition in Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} magnetocaloric compounds

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, R.P. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Sousa, J.B. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal)]. E-mail: jbsousa@fc.up.pt; Correia, F.C. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Araujo, J.P. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Braga, M.E. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Pereira, A.M. [IFIMUP, Rua do Campo Alegre, 678, 4169-007 Porto (Portugal); Morellon, L. [DFMC and ICMA, Univ. De Zaragoza.-CSIC, 50009 Zaragoza (Spain); Algarabel, P.A. [DFMC and ICMA, Univ. De Zaragoza.-CSIC, 50009 Zaragoza (Spain); Magen, C. [DFMC and ICMA, Univ. De Zaragoza.-CSIC, 50009 Zaragoza (Spain); Ibarra, M.R. [DFMC and ICMA, Univ. De Zaragoza.-CSIC, 50009 Zaragoza (Spain)

    2005-04-15

    Recently, the Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} system exhibits fascinating physical properties, namely giant magnetocaloric, magnetoresistance and magnetostriction effects near a first-order (martensitic like; T=T{sub S}) magneto-structural transition. We report the thermopower behavior S(T) between 10 and 300K for compounds with x=0, 0.10 and 0.45, belonging to three distinct regions of the magnetic/structural phase diagram. Large thermopower changes are observed near T{sub S} for x=0.10 (T{sub S}=78K; AFM-Orthorhombic II/FM-Ortho.I) and for x=0.45 (T{sub S}=242K; PM-Monoc/FM-Ortho.I) with a Gaussian distribution in dS/dT, characteristic of a first-order phase transition. Near the purely magnetic transitions (PM/AFM) for x=0(T{sub N}=122K) and x=0.10(T{sub N}=127K) we observe dS/dT peaks governed by spin fluctuation effects. A comparative analysis between dS/dT and the resistivity derivative d{rho}/dT near T{sub S} is made. At low temperatures S(T) behaves similarly in the ferromagnetic x=0.10 and 0.45 compounds (S{approx}AT+BT{sup 2}), the anomalous B term being related to the mean internal field (spin wave excitations). For x=0 (AFM phase at low T) one has S=AT (no B term; zero mean internal field)

  10. The property of Si/SiGe/Si heterostructure during thermal budget characterized by HRXRD

    Institute of Scientific and Technical Information of China (English)

    CHEN Chang-Chun; LIU Zhi-Hong; HUANG Wen-Tao; DOU Wei-Zhi; ZHANG Wei; TSIEN Pei-Hsin; ZHU De-Zhang

    2003-01-01

    Si/SiGe/Si heterostructures grown by ultra-high-vacuum chemical vapor deposition (UHVCVD) werecharacterized by Rutherford backscattering/Channeling (RBS/C) together with high resolution X ray diffraction(HRXRD). High quality SiGe base layer was obtained. The Si/SiGe/Si heterostructures were subject to conventionalfurnace annealing and rapid thermal annealing with temperature between 750 ℃ and 910 ℃. Both strain and its re-laxation degree in SiGe layer are calculated by HRXRD combined with elastic theory, which are never reported inother literatures. The rapid thermal annealing at elevated temperature between 880 ℃ and 910 ℃ for very short timehad almost no influence on the strain in Si0.84Ge0. 16 epilayer. However, high temperature (900℃) furnace annealingfor 1h prompted the strain in Si0.84Ge0.16 layer to relax.

  11. Photoreflectance Spectroscopy for Study of Si/SiGe/Si Heterostructure

    Institute of Scientific and Technical Information of China (English)

    Liu Zhihong; Chen Changchun; Lin Huiwang; Xiong Xiaoyi; Dou Weizhi; Tsien Pei-Hsin

    2004-01-01

    UHVCVD-grown Si/Si1- xGex/Si heterostructure was investigated by Photoreflectance spectroscopy (PR). The principle of PR used in semiconductor film was thoroughly described. According to the E1 transition energy in the Si1- xGex alloy, the Ge content in SiGe film with constant composition can be accurately characterized. In this study, determine the composition uniformity of larger diameter SiGe epiwafer by PR mapping technique was determined. These results show PR is very promising for Si1- xGex epilayer characterization with constant Ge content and can provide film measurements for production-worthy line monitor.

  12. Magnetic structure of CeScSi-type Tb {sub x}Er{sub 1-x}Ti{sub 0.85}Mo{sub 0.15}Ge compounds (x = 0, ?, 1)

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V. [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, Moscow GSP-2 119992 (Russian Federation)]. E-mail: morozkin@general.chem.msu.ru; Nirmala, R. [Tata Institute of Fundamental Research, Mumbai 400005 (India); Halich, K. [Laboratoire de Chimie des metaux de transition, UMR 7513, Institut Le Bel, Universite Louis Pasteur, Strasbourg (France); Malik, S.K. [Tata Institute of Fundamental Research, Mumbai 400005 (India); Welter, R. [Laboratoire de Chimie des metaux de transition, UMR 7513, Institut Le Bel, Universite Louis Pasteur, Strasbourg (France)

    2005-04-19

    Magnetization and neutron diffraction studies have been carried out on CeScSi-type Tb {sub x}Er{sub 1-x}Ti{sub 0.85}Mo{sub 0.15}Ge compounds (space group I4/mmm, no. 139). These compounds demonstrate ferromagnetic collinear 1 (FC1), ferromagnetic collinear 2 (FC2) and ferromagnetic non-collinear 1 (FNC1) types of ordering. Below T {sub FC1} = 131 K for Tb{sub 0.25}Er{sub 0.75}Ti{sub 0.85}Mo{sub 0.15}Ge and T {sub FC1} = 194 K for Tb{sub 0.5}Er{sub 0.5}Ti{sub 0.85}Mo{sub 0.15}Ge the magnetic structure of these compounds consists of ferromagnetic (0 0 2) rare earth double layers with magnetic moments of rare earth atoms the [0, 0, M {sub z}]. Below T {sub FC2} = 242 K for Tb{sub 0.75}Er{sub 0.25}Ti{sub 0.85}Mo{sub 0.15}Ge and T {sub FC2} = 280 K for TbTi{sub 0.85}Mo{sub 0.15}Ge the magnetic structure of these compounds consists of ferromagnetic (0 0 1) layers with magnetic moments of rare earth atoms the [M {sub x}, 0, M {sub z}]. Below T {sub FNC1} = 63 K for ErTi{sub 0.85}Mo{sub 0.15}Ge, T {sub FNC1} = 14 K for Tb{sub 0.5}Er{sub 0.5}Ti{sub 0.85}Mo{sub 0.15}Ge, T {sub FNC1} = 29 K for Tb{sub 0.25}Er{sub 0.75}Ti{sub 0.85}Mo{sub 0.15}Ge and T {sub FNC1} = 75 K for TbTi{sub 0.85}Mo{sub 0.15}Ge the magnetic structure of these compounds consists of ferromagnetic (0 0 2) layers, but the magnetic moments of R atoms in the neighbouring layers are non-collinear.

  13. First principles study of a new half-metallic ferrimagnets Mn{sub 2}-based full Heusler compounds: Mn{sub 2}ZrSi and Mn{sub 2}ZrGe

    Energy Technology Data Exchange (ETDEWEB)

    Abada, A. [Laboratoire d’études physico-chimiques, Université Dr Moulay Tahar, Saida 20000 (Algeria); Amara, K., E-mail: kamaraphy@gmail.com [Laboratoire d’études physico-chimiques, Université Dr Moulay Tahar, Saida 20000 (Algeria); Hiadsi, S. [Département de Génie Physique, Université d’Oran des sciences et de la technologie Mohamed Boudiaf (Algeria); Amrani, B. [Département de Physique, Université d’Oran Es-Senia, Oran 31000 (Algeria)

    2015-08-15

    Half-metallic properties of new predicted Mn{sub 2}-based full Heusler alloys Mn{sub 2}ZrSi and Mn{sub 2}ZrGe have been studied by first-principles full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method based on density functional theory (DFT). Our investigation is focused on the structural, elastic, electronic and magnetic properties of these compounds. The AlCu{sub 2}Mn-type structure is found to be energetically more favorable than the CuHg{sub 2}Ti-type structure for both compounds and are half-metallic ferrimagnets (HMFIs) with total magnetic moments of 2.000µ{sub B} per formula unit, well consistent with Slater–Pauling rule (M{sub tot}=(24–Z{sub tot})µ{sub B}). Calculations show that both the alloys have an indirect band gaps, in the majority-spin channel, with values of 0.505 eV and 0.278 eV for Mn{sub 2}ZrSi and Mn{sub 2}ZrGe, respectively. It was found that Mn{sub 2}ZrSi and Mn{sub 2}ZrGe preserved their half-metallicity for lattice constants range of 5.85–6.38 Å and 6.05–6.38 Å, respectively, and kept a 100% of spin polarization at the Fermi level. Moreover, the calculated formation energies and elastic constants confirm that these compounds are stable chemically and mechanically, and the good crystallographic compatibility with the lattice of semiconductors used industrially makes them promising magnetic materials in spintronic applications. - Highlights: • For Mn{sub 2}ZrZ (Z=Si, Ge) the AlCu{sub 2}Mn-type structure is more favorable than the CuHg{sub 2}Ti-type. • The calculated elastic constants confirm their mechanical stability. • Their negative estimated formation energies means they can be synthesized. • Their lattice constants match well with those of many semiconductor substrates. • They are predicted to be true half-metallic ferrimagnets. • The band gaps of Mn{sub 2}ZrSi~0.51 eV and Mn{sub 2}ZrGe~0.28 eV are indirect along, the Γ–X.

  14. GeSn/Si Avalanche Photodetectors on Si substrates

    Science.gov (United States)

    2016-09-16

    Photodetectors on Si substrates Report Title In this project, firstly, the material growth of GeSn by chemical vapor deposition (CVD) system has been...between GeSn and other market dominating IR detectors in short-IR wavelength (First time reported the D* of a GeSn detector in the world). The D* of...Standard Form 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 Final Report W911NF-13-1-0196 64461-EL-DRP.43 479-575-7265 a. REPORT 14. ABSTRACT 16

  15. Heteroepitaxy of Ge-Si{sub 1{minus}x}Ge{sub x} superlattices on Si (100) substrates by GeH{sub 4}-Si MBE

    Energy Technology Data Exchange (ETDEWEB)

    Orlov, L.K.; Tolomasov, V.A.; Potapov, A.V.; Drozdov, Yu.N. [Russian Academy of Sciences, Nizhny Novgorod (Russian Federation). Inst. for Physics of Microstructures; Vdovin, V.I. [Inst. for Rare Metals Giredmet, Moscow (Russian Federation)

    1996-12-31

    The authors applied GeH{sub 4}-SI MBE for growing Ge-Si{sub 1{minus}x}Ge{sub x} superlattices on Si(100). They investigated the distribution and the structure of defects inside heteroepitaxial Si{sub 1{minus}x}Ge{sub x} layers grown on Si(100). It was shown that the system has unique peculiarities of a dislocation structure formation. They found out that the plastic deformation on a layer-substrate heteroboundary eliminates strong elastic deformation inside the grown layer.

  16. Formation of microtubes from strained SiGe/Si heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Qin, H [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Shaji, N [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Merrill, N E [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Kim, H S [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Toonen, R C [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Blick, R H [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Roberts, M M [Department of Materials Science and Engineering, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706 (United States); Savage, D E [Department of Materials Science and Engineering, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706 (United States); Lagally, M G [Department of Materials Science and Engineering, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706 (United States); Celler, G [SOITEC USA Inc., 2 Centennial Drive, Peabody, MA 01960 (United States)

    2005-11-15

    We report the formation of micrometre-sized SiGe/Si tubes by releasing strained SiGe/Si bilayers from substrates in a wet chemical-etching process. In order to explore statistical studies of dynamic formation of microtubes, we fabricated arrays of square bilayers. Due to the dynamic change in curvature of the bilayers, and hence the underlying etch channels, the etching process deviates from a transport-controlled regime to one of kinetic controlled. We identified two distinct modes of etching. A slow etching mode is associated with symmetric surface deformation in which the bilayers mostly retain their initial pattern. In the fast mode, bilayers are asymmetrically deformed while large etch channels are induced and etching becomes kinetically controlled. Etch rate dispersion is directly related to the degree of asymmetry in surface deformation. When the dimensions of the bilayers become significantly larger than the curvature radius, kinetic etching dominates. During the formation of tubes, SiGe/Si bilayers strongly interact with the liquid environment of etchant and solvent. Assisted by the surface tension of evaporating liquids, the tubes are drawn near the substrate and eventually fixed to it because of van der Waals forces. Our study illuminates the dynamic etching and curling processes involved with and provides insight on how a uniform etch rate and consistent curling directions can be maintained.

  17. Formation of microtubes from strained SiGe/Si heterostructures

    Science.gov (United States)

    Qin, H.; Shaji, N.; Merrill, N. E.; Kim, H. S.; Toonen, R. C.; Blick, R. H.; Roberts, M. M.; Savage, D. E.; Lagally, M. G.; Celler, G.

    2005-11-01

    We report the formation of micrometre-sized SiGe/Si tubes by releasing strained SiGe/Si bilayers from substrates in a wet chemical-etching process. In order to explore statistical studies of dynamic formation of microtubes, we fabricated arrays of square bilayers. Due to the dynamic change in curvature of the bilayers, and hence the underlying etch channels, the etching process deviates from a transport-controlled regime to one of kinetic controlled. We identified two distinct modes of etching. A slow etching mode is associated with symmetric surface deformation in which the bilayers mostly retain their initial pattern. In the fast mode, bilayers are asymmetrically deformed while large etch channels are induced and etching becomes kinetically controlled. Etch rate dispersion is directly related to the degree of asymmetry in surface deformation. When the dimensions of the bilayers become significantly larger than the curvature radius, kinetic etching dominates. During the formation of tubes, SiGe/Si bilayers strongly interact with the liquid environment of etchant and solvent. Assisted by the surface tension of evaporating liquids, the tubes are drawn near the substrate and eventually fixed to it because of van der Waals forces. Our study illuminates the dynamic etching and curling processes involved with and provides insight on how a uniform etch rate and consistent curling directions can be maintained.

  18. Si/SiGe/Si HBT的直流特性和低频噪声%Si/SiGe/Si HBT's DC Characterization and Its Low-frequency Noise

    Institute of Scientific and Technical Information of China (English)

    廖小平; 张中平

    2003-01-01

    在对Si/SiGe/Si HBT及其Si兼容工艺的研究基础上,研制成功低噪声Si/SiGe/Si HBT,测试和分析了它的直流特性和低频噪声特性,为具有更好的低噪声性能的Si/SiGe/Si HBT的研究建立了基础.

  19. Evolution of Ge and SiGe Quantum Dots under Excimer Laser Annealing

    Institute of Scientific and Technical Information of China (English)

    HAN Gen-Quan; ZENG Yu-Gang; YU Jin-Zhong; CHENG Bu-Wen; YANG Hai-Tao

    2008-01-01

    We present different relaxation mechanisms of Ge and SiGe quantum dots under excimer laser annealing.Inyestigation of the coarsening and relaxation of the dots showS that the strain in Ge dots on Ge films is relaxed by dislocation since there is no interface between the Ge dots and the Ge layer,while the SiGe dots on Si0.77 Ge0.23film relax by lattice distortion to coherent dots which results from the obvious interface between the SiGe dots and the Si0.77Ge0.23 film.The results are suggested and sustained by Vanderbilt and Wickham's theory,and also demonstrate that no bulk diffusion Occurs during the excimer laser annealing.

  20. Study of Si-Ge interdiffusion with phosphorus doping

    KAUST Repository

    Cai, Feiyang

    2016-10-28

    Si-Ge interdiffusion with phosphorus doping was investigated by both experiments and modeling. Ge/Si1-x Ge x/Ge multi-layer structures with 0.75Ge<1, a mid-1018 to low-1019 cm−3 P doping, and a dislocation density of 108 to 109 cm−2 range were studied. The P-doped sample shows an accelerated Si-Ge interdiffusivity, which is 2–8 times of that of the undoped sample. The doping dependence of the Si-Ge interdiffusion was modelled by a Fermi-enhancement factor. The results show that the Si-Ge interdiffusion coefficient is proportional to n2/n2i for the conditions studied, which indicates that the interdiffusion in a high Ge fraction range with n-type doping is dominated by V2− defects. The Fermi-enhancement factor was shown to have a relatively weak dependence on the temperature and the Ge fraction. The results are relevant to the structure and thermal processing condition design of n-type doped Ge/Si and Ge/SiGe based devices such as Ge/Si lasers.

  1. Bi surfactant mediated growth for fabrication of Si/Ge nanostructures and investigation of Si/Ge intermixing by STM

    Energy Technology Data Exchange (ETDEWEB)

    Paul, N.

    2007-10-26

    In the thesis work presented here, we show that Bi is more promising surfactant material than Sb. We demonstrate that by using Bi as a terminating layer on Ge/Si surface, it is possible to distinguish between Si and Ge in Scanning tunnelling microscope (STM). Any attempt to utilize surfactant mediated growth must be preceded by a thorough study of its effect on the the system being investigated. Thus, the third chapter of this thesis deals with an extensive study of the Bi surfactant mediated growth of Ge on Si(111) surface as a function of Ge coverage. The growth is investigated from the single bilayer Ge coverage till the Ge coverage of about 15 BL when the further Ge deposition leads to two-dimensional growth. In the fourth chapter, the unique property of Bi terminating layer on Ge/Si surface to result in an STM height contrast between Si and Ge is explained with possible explanations given for the reason of this apparent height contrast. The controlled fabrication of Ge/Si nanostructures such as nanowires and nanorings is demonstrated. A study on Ge-Si diffusion in the surface layers by a direct method such as STM was impossible previously because of the similar electronic structure of Ge and Si. Since with the Bi terminating surface layer, one is able to distinguish between Ge and Si, the study of intermixing between them is also possible using STM. This method to distinguish between Si and Ge allows one to study intermixing on the nanoscale and to identify the fundamental diffusion processes giving rise to the intermixing. In Chapter 5 we discuss how this could prove useful especially as one could get a local probe over a very narrow Ge-Si interface. A new model is proposed to estimate change in the Ge concentration in the surface layer with time. The values of the activation energies of Ge/Si exchange and Si/Ge exchange are estimated by fitting the experimental data with the model. The Ge/Si intermixing has been studied on a surface having 1 ML Bi ({radical

  2. Analysis of Si/SiGe Heterostructure Solar Cell

    Directory of Open Access Journals (Sweden)

    Ashish Kumar Singh

    2014-01-01

    Full Text Available Sunlight is the largest source of carbon-neutral energy. Large amount of energy, about 4.3 × 1020 J/hr (Lewis, 2005, is radiated because of nuclear fusion reaction by sun, but it is unfortunate that it is not exploited to its maximum level. Various photovoltaic researches are ongoing to find low cost, and highly efficient solar cell to fulfil looming energy crisis around the globe. Thin film solar cell along with enhanced absorption property will be the best, so combination of SiGe alloy is considered. The paper presented here consists of a numerical model of Si/Si1-xGex heterostructure solar cell. The research has investigated characteristics such as short circuit current density (Jsc, generation rate (G, absorption coefficient (α, and open circuit voltage (Voc with optimal Ge concentration. The addition of Ge content to Si layer will affect the property of material and can be calculated with the use of Vegard’s law. Due to this, short circuit current density increases.

  3. Ether-like Si-Ge hydrides for applications in synthesis of nanostructured semiconductors and dielectrics.

    Science.gov (United States)

    Tice, Jesse B; Weng, Change; Tolle, John; D'Costa, Vijay R; Singh, Rachna; Menendez, Jose; Kouvetakis, John; Chizmeshya, Andrew V G

    2009-09-14

    Hydrolysis reactions of silyl-germyl triflates are used to produce ether-like Si-Ge hydride compounds including H(3)SiOSiH(3) and the previously unknown O(SiH(2)GeH(3))(2). The structural, energetic and vibrational properties of the latter were investigated by experimental and quantum chemical simulation methods. A combined Raman, infrared and theoretical analysis indicated that the compound consists of an equal mixture of linear and gauche isomers in analogy to the butane-like H(3)GeSiH(2)SiH(2)GeH(3) with an exceedingly small torsional barrier of approximately 0.2 kcal mol(-1). This is also corroborated by thermochemistry simulations which indicate that the energy difference between the isomers is less than 1 kcal mol(-1). Proof-of-principle depositions of O(SiH(2)GeH(3))(2) at 500 degrees C on Si(100) yielded nearly stoichiometric Si(2)Ge(2)O materials, closely reflecting the composition of the molecular core. A complete characterization of the film by RBS, XTEM, Raman and IR ellipsometry revealed the presence of Si(0.30)Ge(0.70) quantum dots embedded within an amorphous matrix of Si-Ge-O suboxide, as required for the fabrication of high performance nonvolatile memory devices. The use of readily available starting materials coupled with facile purification and high yields also makes the above molecular approach an attractive synthesis route to H(3)SiOSiH(3) with industrial applications in the formation of Si-O-N high-k gate materials in high-mobility SiGe based transistors.

  4. Exploration of R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge): Structural Motifs, the novel Compound Gd2AlGe2 and Analysis of the U3Si2 and Zr3Al2 Structure Types

    Energy Technology Data Exchange (ETDEWEB)

    McWhorter, Sean William [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    In the process of exploring and understanding the influence of crystal structure on the system of compounds with the composition Gd5(SixGe1-x)4 several new compounds were synthesized with different crystal structures, but similar structural features. In Gd5(SixGe1-x)4, the main feature of interest is the magnetocaloric effect (MCE), which allows the material to be useful in magnetic refrigeration applications. The MCE is based on the magnetic interactions of the Gd atoms in the crystal structure, which varies with x (the amount of Si in the compound). The crystal structure of Gd5(SixGe1-x)4 can be thought of as being formed from two 32434 nets of Gd atoms, with additional Gd atoms in the cubic voids and Si/Ge atoms in the trigonal prismatic voids. Attempts were made to substitute nonmagnetic atoms for magnetic Gd using In, Mg and Al. Gd2MgGe2 and Gd2InGe2 both possess the same 32434 nets of Gd atoms as Gd5(SixGe1-x)4, but these nets are connected differently, forming the Mo2FeB2 crystal structure. A search of the literature revealed that compounds with the composition R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge) crystallize in one of four crystal structures: the Mo2FeB2, Zr3Al2, Mn2AlB2 and W2CoB2 crystal structures. These crystal structures are described, and the relationships between them are highlighted. Gd2AlGe2 forms an entirely new crystal structure, and the details of its synthesis and characterization are given. Electronic structure calculations are performed to understand the nature of bonding in this compound and how

  5. Neutron diffraction study of the La1-xPrxMn2Si2 ( x=0.4, 0.7 and 1) compounds and the general description of the magnetic behavior of Mn in RMn2Ge2 and RMn2Si2

    Science.gov (United States)

    Dincer, I.; Elerman, Y.; Elmali, A.; Ehrenberg, H.; André, G.

    2007-06-01

    The magnetic structures of the La1-xPrxMn2Si2 ( x=0.4, 0.7 and 1) have been investigated by powder neutron diffraction between 2 and 308 K. According to magnetic measurements, the x=0.4 sample shows a typical SmMn2Ge2-like magnetic behavior. Neutron diffraction indicates a canted antiferromagnetic structure below 130 K and a canted ferromagnetic structure above 240 K. Between 130 and 240 K, the canted ferromagnetic and antiferromagnetic structures coexist. Since the magnetic moments of Mn atoms, the unit cell parameters and the scale parameters of the canted antiferromagnetism and canted ferromagnetism are highly correlated between 130 and 240 K, a special refinement procedure was introduced. The critical Mn-Mn value was determined as 2.87 A˚, and the spontaneous volume change and linear magnetostriction are derived. Neutron diffraction revealed a canted antiferromagnetic structure for La0.3Pr0.7Mn2Si2. A canted antiferromagnetic structure was also detected for PrMn2Si2 by neutron diffraction in contrast to previous reports of a collinear arrangement. The present results are compiled together with previous ones on RMn2Ge2 and RMn2Si2 (R: Y, La and rare-earth) compounds in two magnetic phase diagrams. These two graphics summarize the general magnetic behavior of Mn in the RMn2Ge2 and RMn2Si2 compounds.

  6. A comparative study of electroluminescence from Ge/SiO2 and Si/SiO2 films

    Institute of Scientific and Technical Information of China (English)

    Ma Shu-Yi; Chen Hui; Xiao Yong; Ma Zi-Jun; Sun Ai-Min

    2004-01-01

    Ge/SiO2 and Si/SiO2 films were deposited using the two-target alternation magnetron sputtering technique. The Au/Ge/SiO2/p-Si and Au/Si/SiO2/p-Si structures were fabricated and their electroluminescence (EL) characteristics were comparatively studied. Both Au/Ge/SiO2/p-Si and Au/Si/SiO2/p-Si structures have rectifying property. All the EL spectra from the two types of the structure have peak positions around 650-660 nm. The EL mechanisms of the structures are discussed.

  7. The effects of strain on indirect absorption in Ge/SiGe quantum wells

    Science.gov (United States)

    Lever, L.; Ikonić, Z.; Kelsall, R. W.

    2012-06-01

    We calculate the conduction band electron scattering rates from the Γ-valley into the indirect valleys in germanium, and use this to determine the strength of the indirect absorption in Ge/SiGe quantum well heterostructures. This is done as a function of the in-plane compressive strain in the Ge quantum wells, which results from pseudomorphic growth on a SiGe virtual substrate. This compressive strain results in the Δ valleys becoming available as destination states for scattering, which leads to a reduction in the Γ-valley lifetime. We calculate the indirect absorption and lifetime broadening of excitonic peaks, and show that indirect absorption decreases as the Ge fraction in the virtual substrate increases. We conclude that the Ge fraction of the SiGe virtual substrate should be approximately 95% or larger for optimum electroabsorption performance of Ge/SiGe quantum wells.

  8. Non-Selective SiGe Graphic Epitaxial by MBE

    Institute of Scientific and Technical Information of China (English)

    Qian Zhou; Chun Han; Jing-Chun Li

    2007-01-01

    To handle the thermal budget in SiGe BiCMOS process, a nonselective graphic epitaxial technology using molecular beam epitaxial (MBE) has been developed. SEM, AFM, XRD, and dislocation density measurements are carried out. The SiGe film's RMS roughness is 0.45nm, and dislocation density is 0.3×103cm2~1.2×103cm2. No dislocation accumulation exists on the boundary of the windows; this indicates the high quality of the SiGe film. The experiment results show that the technology presented in this paper meets the fabrication requirements of SiGe BiCMOS.

  9. GeSn/SiGeSn photonic devices for mid-infrared applications: experiments and calculations

    Science.gov (United States)

    Han, Genquan; Zhang, Qingfang; Liu, Yan; Zhang, Chunfu; Hao, Yue

    2016-11-01

    In this work, a fully strained GeSn photodetector with Sn atom percent of 8% is fabricated on Ge buffer on Si(001) substrate. The wavelength λ of light signals with obvious optical response for Ge0.92Sn0.08 photodetector is extended to 2 μm. The impacts of compressive strain introduced during the epitaxial growth of GeSn on Ge/Si are studied by simulation. Besides, the tensile strain engineering of GeSn photonic devices is also investigated. Lattice-matched GeSn/SiGeSn double heterostructure light emitting diodes (LEDs) with Si3N4 tensile liner stressor are designed to promote the further mid-infrared applications of GeSn photonic devices. With the releasing of the residual stress in Si3N4 liner, a large biaxial tensile strain is induced in GeSn active layer. Under biaxial tensile strain, the spontaneous emission rate rsp and internal quantum efficiency ηIQE for GeSn/SiGeSn LED are significantly improved.

  10. Structural and Compositional Properties of Strain-Symmetrized SiGe/Si Heterostructures

    Science.gov (United States)

    Ross, I. M.; Gass, M.; Walther, T.; Bleloch, A.; Cullis, A. G.; Lever, L.; Ikonic, Z.; Califano, M.; Kelsall, R. W.; Zhang, J.; Paul, D. J.

    In this study, we have utilised conventional and aberration corrected (scanning) transmission electron microscopy to examine the Ge concentration across a series of technologically significant SiGe/Si prototype heterostructures. Electron energy loss line profiles show that the Ge concentration within the SiGe quantum wells approaches the nominal values. However, the Ge concentration profile shows that the interfaces are not abrupt and that the narrow 0.8nm barrier layer does not reach the nominal pure Si composition. Speculation as to the presence of Ge interdiffusion, surface segregation or interface roughness is discussed.

  11. Ge nanobelts with high compressive strain fabricated by secondary oxidation of self-assembly SiGe rings

    DEFF Research Database (Denmark)

    Lu, Weifang; Li, Cheng; Lin, Guangyang

    2015-01-01

    Curled Ge nanobelts were fabricated by secondary oxidation of self-assembly SiGe rings, which were exfoliated from the SiGe stripes on the insulator. The Ge-rich SiGe stripes on insulator were formed by hololithography and modified Ge condensation processes of Si0.82Ge0.18 on SOI substrate. Ge na...... nanobelts, which extrudes to Ge nanobelts in radial and tangent directions during the cooling process. This technique is promising for application in high-mobility Ge nano-scale transistors...

  12. Magnetic structure of Gd5Si2Ge2 and Gd5Si2Ge1.9M0.1 (M = Ga, Cu).

    Science.gov (United States)

    Palacios, E; Rodríguez-Velamazán, J A; Wang, G F; Burriel, R; Cuello, G; Rodríguez-Carvajal, J

    2010-11-10

    Powder x-ray diffraction patterns of the doped compounds Gd(5)Si(2)Ge(1.9)M(0.1) (M = Ga, Cu) show the same crystal structure, orthorhombic Gd(5)Si(4)-type, in the ferromagnetic and paramagnetic phases. This is different from Gd(5)Si(2)Ge(2), whose paramagnetic phase is monoclinic. The magnetic structure at low temperature, solved from diffraction experiments with hot neutrons, is the same in all the three compounds, collinear ferromagnetic with moments along the crystal b-axis, or F(y)F(By) according to Bertaut's notation. These results, combined with those of heat capacity and magnetocaloric effect, indicate, similarly to Gd(5)Si(4), a second-order, purely magnetic, transition in the doped compounds explaining the absence of hysteresis.

  13. N-Heterocyclic Carbene Coinage Metal Complexes of the Germanium-Rich Metalloid Clusters [Ge9R3]− and [Ge9RI2]2− with R = Si(iPr3 and RI = Si(TMS3

    Directory of Open Access Journals (Sweden)

    Felix S. Geitner

    2017-07-01

    Full Text Available We report on the synthesis of novel coinage metal NHC (N-heterocyclic carbene compounds of the germanium-rich metalloid clusters [Ge9R3]− and [Ge9RI2]2− with R = Si(iPr3 and RI = Si(TMS3. NHCDippCu{η3Ge9R3} with R = Si(iPr3 (1 represents a less bulky silyl group-substituted derivative of the known analogous compounds with R = Si(iBu3 or Si(TMS3. The coordination of the [NHCDippCu]+ moiety to the cluster unit occurs via one triangular face of the tri-capped trigonal prismatic [Ge9] cluster. Furthermore, a series of novel Zintl cluster coinage metal NHC compounds of the type (NHCM2{η3Ge9RI2} (RI = Si(TMS3 M = Cu, Ag and Au; NHC = NHCDipp or NHCMes is presented. These novel compounds represent a new class of neutral dinuclear Zintl cluster coinage metal NHC compounds, which are obtained either by the stepwise reaction of a suspension of K12Ge17 with Si(TMS3Cl and the coinage metal carbene complexes NHCMCl (M = Cu, Ag, Au, or via a homogenous reaction using the preformed bis-silylated cluster K2[Ge9(Si(TMS32] and the corresponding NHCMCl (M = Cu, Ag, Au complex. The molecular structures of NHCDippCu{η3Ge9(Si(iPr33} (1 and (NHCDippCu2{η3-Ge9(Si(TMS32} (2 were determined by single crystal X-ray diffraction methods. In 2, the coordination of the [NHCDippCu]+ moieties to the cluster unit takes place via both open triangular faces of the [Ge9] entity. Furthermore, all compounds were characterized by means of NMR spectroscopy (1H, 13C, 29Si and ESI-MS.

  14. Structural and optical properties of Er{sup 3+} doped SiO{sub 2}–Al{sub 2}O{sub 3}–GeO{sub 2} compounds prepared by a simple route

    Energy Technology Data Exchange (ETDEWEB)

    Filho, Fausto M. Faria [Instituto de Física, Universidade Federal de Goiás-UFG, Campus II, Caixa Postal 131, CEP 74001-970 Goiânia, GO (Brazil); Gonçalves, Rogéria R. [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo-USP, Av. Bandeirantes, 3900, CEP 14040-901 Ribeirão Preto, SP (Brazil); Ribeiro, Sidney J.L. [Institute of Chemistry, São Paulo State University-UNESP, Rua Professor Francisco Degni, 55, CEP 14801-970 Araraquara, SP (Brazil); Maia, Lauro J.Q., E-mail: lauro@ufg.br [Instituto de Física, Universidade Federal de Goiás-UFG, Campus II, Caixa Postal 131, CEP 74001-970 Goiânia, GO (Brazil)

    2015-04-15

    Highlights: • We developed a simple route to obtain gels and powders using GeO{sub 2}, TEOS and TMAH solution. • Al{sub 6}Ge{sub 2}O{sub 13} crystalline nanoparticles embedded in amorphous matrix were obtained. • The Al{sub 2}O{sub 3} enhance Er{sup 3+} dispersion in GeO{sub 2}–SiO{sub 2} increasing its emission and the full width at half maximum from 41 to 56 nm. • The {sup 4}I{sub 13/2} Er{sup 3+} level lifetime varies between 4.8 and 5.6 ms (1533 nm emission). - Abstract: Samples of (1 − x)[0.70SiO{sub 2} + 0.30Al{sub 2}O{sub 3}] + xGeO{sub 2} compositions, containing x = 0.05, 0.10, 0.20, 0.30, 0.40 and 0.50, and doped with 1 mol% of Er{sup 3+}, were prepared by a mixed route (sol–gel process and Pechini method). Transparent gels were synthesized and homogeneous powders were obtained by heat treatments from 800 °C to 1050 °C. The final powders were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and high-resolution transmission electron microscopy. The optical properties were studied by photoluminescence measurements in the infrared region, and the average lifetime of the metastable state {sup 4}I{sub 13/2} of Er{sup 3+} ions and the full-width at half maximum (FWHM) were determined. A silica-rich amorphous phase and nanocrystallites with orthorhombic structure of Al{sub 6}Ge{sub 2}O{sub 13} phase were obtained. The samples present a broad emission centered at around 1532 nm under excitation at 977 nm, with a FWHM of 53 nm and a lifetime of 5.6 ms. The synthesized compounds by an easy chemical procedure are potentially applicable in integrated optical systems.

  15. Monolithically Integrated Ge-on-Si Active Photonics

    OpenAIRE

    Jifeng Liu

    2014-01-01

    Monolithically integrated, active photonic devices on Si are key components in Si-based large-scale electronic-photonic integration for future generations of high-performance, low-power computation and communication systems. Ge has become an interesting candidate for active photonic devices in Si photonics due to its pseudo-direct gap behavior and compatibility with Si complementary metal oxide semiconductor (CMOS) processing. In this paper, we present a review of the recent progress in Ge-on...

  16. Transport and magnetic study of the spin reorientation transition in the Tb{sub 5}(Si{sub 0.5}Ge{sub 0.5}){sub 4} magnetocaloric compound

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, J P [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Pereira, A M [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Braga, M E [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Pinto, R P [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Teixeira, J M [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Correia, F C [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Sousa, J B [IFIMUP and Physics Department of FCUP, University of Porto, R. Campo Alegre 687, Porto 4169-007 (Portugal); Morellon, L [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones CientIficas and Instituto de Nanociencia de Aragon, 50009 Zaragoza (Spain); Algarabel, P A [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones CientIficas, 50009 Zaragoza (Spain); Magen, C [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones CientIficas, 50009 Zaragoza (Spain); Ibarra, M R [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones CientIficas and Instituto de Nanociencia de Aragon, 50009 Zaragoza (Spain)

    2005-08-17

    Detailed measurements of the electrical resistivity {rho}(T), thermopower S(T) and magnetization of Tb{sub 5}(Si{sub 0.5}Ge{sub 0.5}){sub 4} in the vicinity of the spin reorientation transitions observed in this compound are reported. Our results indicate a complex spin reorientation process associated with three different lattice sites occupied by the Tb ions. We identify two critical transition temperatures: one at T{sub SR{sub 1}} = 57 K, as previously reported, and a new one at T{sub SR{sub 2}} = 40 K. A simple model based on an approximate magnetic anisotropy energy is presented; it gives a satisfactory qualitative description of the main features of the reorientation processes.

  17. Segregation of Ge in B and Ge codoped Czochralski-Si crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Arivanandhan, Mukannan, E-mail: rmarivu@ipc.shizuoka.ac.jp [Department of Electronics and Materials Science, Graduate School of Engineering, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan); Research Institute of Electronics, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan); Gotoh, Raira; Fujiwara, Kozo; Uda, Satoshi [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Hayakawa, Yasuhiro [Department of Electronics and Materials Science, Graduate School of Engineering, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan); Research Institute of Electronics, Shizuoka University, Johoku 3-5-1, Naka-Ku, Hamamatsu 432-8011 (Japan)

    2015-08-05

    Highlights: • Effective segregation of Ge in B and Ge codoped Czochralski-Si crystal growth was analyzed. • The equilibrium segregation coefficient of Ge was calculated. • The experimentally results were analytically analyzed using partitioning theory. - Abstract: The segregation of Ge in B and Ge codoped Czochralski (CZ)-Si crystal growth was investigated. The concentration of Ge in heavily Ge codoped CZ-Si was measured by electron probe micro analysis (EPMA) and X-ray fluorescence spectroscopy. The effective segregation coefficient of Ge (k{sub eff}) was calculated by fitting the EPMA data to the normal freezing equation, and by taking the logarithmic ratio of the Ge concentrations at the seed and tail of the ingots (top to bottom approach). The k{sub eff} of Ge increased from 0.30 to 0.55, when the initial Ge concentration in the Si melt (C{sub L(o)}{sup Ge}) was increased from 3 × 10{sup 19} to 3 × 10{sup 21} cm{sup −3}. To avoid cellular growth, the crystal pulling rate was decreased for heavily Ge codoped crystal growth (C{sub L(o)}{sup Ge} > 3 × 10{sup 20} cm{sup −3}). The equilibrium segregation coefficient (k{sub 0}) of Ge was calculated by partitioning theory, and was smaller than the experimentally estimated k{sub eff}. The variation of k{sub eff} from k{sub 0} was discussed based on Ge clustering in the heavily Ge codoped crystal, which led to changes in the bonding and strain energies caused by the incorporation of Ge into Si.

  18. Crystal structure of the Nd(Ru{sub 0.6}Ge{sub 0.4}){sub 2} and ErRuGe compounds

    Energy Technology Data Exchange (ETDEWEB)

    Rizzoli, C.; Sologub, O.; Salamakha, P

    2003-02-17

    Using X-ray powder and single crystal diffraction, the crystal structures of the Nd(Ru{sub 0.6}Ge{sub 0.4}){sub 2} and ErRuGe compounds were investigated. The compounds belong to the KHg{sub 2} and TiNiSi type structure, respectively.

  19. Formation and function of vacancies in Si/Ge Clathrates: The importance of broken symmetries

    Science.gov (United States)

    Bhattacharya, Amrita; Carbogno, Christian; Scheffler, Matthias; Dr. Matthias Scheffler Team, Prof.

    2015-03-01

    One promising material class for improved thermoelectrics are the clathrates, i.e., semiconducting host lattices encapsulating guest atom. Even in simple clathrates, such as, Si46 and Ge46, the introduction of guests can result in important but not yet understood effects: In Si hosts, the addition of K (or Ba) results in defect-free K8Si46 (Ba8Si46) phases. In spite of their structural and electronic similitude, Ge hosts behave fundamentally different upon filling, where, the spontaneously formed framework vacancies completely (or partially) balance the electron donated by K (or Ba) guests leading to K8Ge44(orBa8Ge43) clathrates. In this work, we use density-functional theory, carefully validating the exchange correlation functional, to compute the formation energies of vacancies and vacancy complexes in Si- and Ge-hosts as function of the filling of guests. By taking into account of the structural disorder, geometric relaxations, and vibrational entropies, we verify the experimentally found vacancy concentration and the thermodynamic stabilities of these compounds. We can trace back the contrasting behaviour of Si/Ge clathrates upon filling to a curious, charged vacancy induced break in symmetry that occurs in Si but not in Ge hosts.

  20. (Si)GeSn nanostructures for light emitters

    Science.gov (United States)

    Rainko, D.; Stange, D.; von den Driesch, N.; Schulte-Braucks, C.; Mussler, G.; Ikonic, Z.; Hartmann, J. M.; Luysberg, M.; Mantl, S.; Grützmacher, D.; Buca, D.

    2016-05-01

    Energy-efficient integrated circuits for on-chip or chip-to-chip data transfer via photons could be tackled by monolithically grown group IV photonic devices. The major goal here is the realization of fully integrated group IV room temperature electrically driven lasers. An approach beyond the already demonstrated optically-pumped lasers would be the introduction of GeSn/(Si)Ge(Sn) heterostructures and exploitation of quantum mechanical effects by reducing the dimensionality, which affects the density of states. In this contribution we present epitaxial growth, processing and characterization of GeSn/(Si)Ge(Sn) heterostructures, ranging from GeSn/Ge multi quantum wells (MQWs) to GeSn quantum dots (QDs) embedded in a Ge matrix. Light emitting diodes (LEDs) were fabricated based on the MQW structure and structurally analyzed via TEM, XRD and RBS. Moreover, EL measurements were performed to investigate quantum confinement effects in the wells. The GeSn QDs were formed via Sn diffusion /segregation upon thermal annealing of GeSn single quantum wells (SQW) embedded in Ge layers. The evaluation of the experimental results is supported by band structure calculations of GeSn/(Si)Ge(Sn) heterostructures to investigate their applicability for photonic devices.

  1. Behaviour of Oxygen-Implanted and Hydrogen-Implanted SiGe/Si Heterostructures

    Institute of Scientific and Technical Information of China (English)

    安正华; 张苗; 门传玲; 沈勤我; 林梓鑫; 李开成; 林成鲁

    2002-01-01

    For SiGe-on-insulator fabrication, a l00nm SiGe tilm with uniform germanium composition was grown on a Si(l00) substrate using a molecular beam epitaxy system without a graded SiGe buffer layer. The samples were implanted by oxygen ions at an energy of 45kev and a dose of 3 × 1017 cm-2, and annealed for five hours at 1250°C in flowing (Ar + 5% 02) atmosphere with a l00nm oxide protective layer. The result indicates that a buried oxide layer was successfully formed at the interface of SiGe and Si on the substrate. Furthermore,hydrogen was implanted into SiGe at the energy of 62keV and the dose of 6 × 1016 cm-2 to perform a blistering study, which confirmed the feasibility of H-induced layer splitting in SiGe layer.

  2. Crystal Chemistry of the New Families of Interstitial Compounds R6Mg23C (R = La, Ce, Pr, Nd, Sm, or Gd) and Ce6Mg23Z (Z = C, Si, Ge, Sn, Pb, P, As, or Sb).

    Science.gov (United States)

    Wrubl, Federico; Manfrinetti, Pietro; Pani, Marcella; Solokha, Pavlo; Saccone, Adriana

    2016-01-01

    The crystal chemical features of the new series of compounds R6Mg23C with R = La-Sm or Gd and Ce6Mg23Z with Z = C, Si, Ge, Sn, Pb, P, As, or Sb have been studied by means of single-crystal and powder X-ray diffraction techniques. All phases crystallize with the cubic Zr6Zn23Si prototype (cF120, space group Fm3̅m, Z = 4), a filled variant of the Th6Mn23 structure. While no Th6Mn23-type binary rare earth-magnesium compound is known to exist, the addition of a third element Z (only 3 atom %), located into the octahedral cavity of the Th6Mn23 cell (Wyckoff site 4a), stabilizes this structural arrangement and makes possible the formation of the ternary R6Mg23Z compounds. The results of both structural and topological analyses as well as of LMTO electronic structure calculations show that the interstitial element plays a crucial role in the stability of these phases, forming a strongly bonded [R6Z] octahedral moiety spaced by zeolite cage-like [Mg45] clusters. Considering these two building units, the crystal structure of these apparently complex intermetallics can be simplified to the NaCl-type topology. Moreover, a structural relationship between RMg3 and R6Mg23C compounds has been unveiled; the latter can be described as substitutional derivatives of the former. The geometrical distortions and the consequent symmetry reduction that accompany this transformation are explicitly described by means of the Bärnighausen formalism within group theory.

  3. Synthesis of Ge nanocrystals embedded in a Si host matrix

    Science.gov (United States)

    Ngiam, Shih-Tung; Jensen, Klavs F.; Kolenbrander, K. D.

    1994-12-01

    The synthesis of a composite material consisting of Ge nanoclusters (greater than or equal to 2 nm in diameter) embedded in a Si host matrix is reported. The Ge nanoparticles are produced by pulsed laser ablation and are codeposited in a Si film simultaneously grown by chemical beam epitaxy using disilane. Scanning transmission electron microscopy, combined with energy-dispersive x-ray measurements, show that discrete Ge particles (greater than or equal to 2 nm diameter) are deposited within a polycrystalline Si host matrix. High-resolution transmission electron microscopy reveals that the paricles are crystalline with a lattice spacing corresponding to that of Ge. The enhancement of Si deposition rates from silanes in the presence of Ge, previously demonstrated in chemical vapor deposition of Si(1 - x)Ge(x) alloys, is shown to facilitate the growth of a Si layer around the Ge nanocrystals. The overall composition of the Ge cluster/Si host composite material is determined by Rutherford backscattering measurements.

  4. Structural and Magnetothermal Properties of Compounds: Yb5SixGe4-x,Sm5SixGe4-x, EuO, and Eu3O4

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Kyunghan [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    The family of R5SixGe4-x alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R5SixGe4-x systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R5SixGe4-x pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R5SixGe4-x systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb5SixGe4-xand Sm5SixGe4-x pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb5SixGe4-x alloys with 0 ≤ x ≤ 4 have been examined by using single crystal and powder x-ray diffraction at room temperature, and dc magnetization and heat capacity measurements between 1.8 K and 400 K in magnetic fields ranging from 0 to 7 T. Unlike the majority of R5SixGe4-x systems studied to date, where R is the rare earth metal, all Yb-based germanide-silicides with the 5:4 stoichiometry crystallize in the same Gd5Si4-type structure. The magnetic properties of Yb5SixGe4-x materials are nearly composition

  5. Electrical Performance of Electron Irradiated SiGe HBT and Si BJT

    Institute of Scientific and Technical Information of China (English)

    Wentao HUANG; Jilin WANG; Zhinong LIU; Peiyi CHEN; Peihsin TSIEN; Xiangti MENG

    2004-01-01

    The change of electrical performances of 1 MeV electron irradiated silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) and Si bipolar junction transistor (BJT) was studied. After electron irradiation, both the collector current IC and the base current IB changed a little, and the current gainβ decreased a little for SiGe HBT. The higher the electron irradiation fluence was, the lower the IC decreased. For conventional Si BJT, IC and IB increased as well asβ decreased much larger than SiGe HBT under the same fluence. The contribution of IB was more important to the degradation ofβ for both SiGeHBT and Si BJT. It was shown that SiGe HBT had a larger anti-radiation threshold and better anti-radiation performance than Si BJT. The mechanism of electrical performance changes induced by irradiation was preliminarily discussed.

  6. Neutron diffraction study of the La{sub 1-x}Pr{sub x}Mn{sub 2}Si{sub 2} (x=0.4, 0.7 and 1) compounds and the general description of the magnetic behavior of Mn in RMn{sub 2}Ge{sub 2} and RMn{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Dincer, I. [Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100 Besevler-Ankara (Turkey)]. E-mail: idincer@eng.ankara.edu.tr; Elerman, Y. [Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100 Besevler-Ankara (Turkey); Elmali, A. [Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100 Besevler-Ankara (Turkey); Ehrenberg, H. [Institute for Materials Science, Darmstadt University of Technology, Petersenstrasse 23, D-64287 Darmstadt (Germany); Andre, G. [Laboratoire Leon Brillouin (CEA-CNRS), CEN-Saclay, 91191 Gif-Sur-Yvette (France)

    2007-06-15

    The magnetic structures of the La{sub 1-x}Pr{sub x}Mn{sub 2}Si{sub 2} (x=0.4, 0.7 and 1) have been investigated by powder neutron diffraction between 2 and 308K. According to magnetic measurements, the x=0.4 sample shows a typical SmMn{sub 2}Ge{sub 2}-like magnetic behavior. Neutron diffraction indicates a canted antiferromagnetic structure below 130K and a canted ferromagnetic structure above 240K. Between 130 and 240K, the canted ferromagnetic and antiferromagnetic structures coexist. Since the magnetic moments of Mn atoms, the unit cell parameters and the scale parameters of the canted antiferromagnetism and canted ferromagnetism are highly correlated between 130 and 240K, a special refinement procedure was introduced. The critical Mn-Mn value was determined as 2.87Angst, and the spontaneous volume change and linear magnetostriction are derived. Neutron diffraction revealed a canted antiferromagnetic structure for La{sub 0.3}Pr{sub 0.7}Mn{sub 2}Si{sub 2}. A canted antiferromagnetic structure was also detected for PrMn{sub 2}Si{sub 2} by neutron diffraction in contrast to previous reports of a collinear arrangement. The present results are compiled together with previous ones on RMn{sub 2}Ge{sub 2} and RMn{sub 2}Si{sub 2} (R: Y, La and rare-earth) compounds in two magnetic phase diagrams. These two graphics summarize the general magnetic behavior of Mn in the RMn{sub 2}Ge{sub 2} and RMn{sub 2}Si{sub 2} compounds.

  7. Monolithically Integrated Ge-on-Si Active Photonics

    Directory of Open Access Journals (Sweden)

    Jifeng Liu

    2014-07-01

    Full Text Available Monolithically integrated, active photonic devices on Si are key components in Si-based large-scale electronic-photonic integration for future generations of high-performance, low-power computation and communication systems. Ge has become an interesting candidate for active photonic devices in Si photonics due to its pseudo-direct gap behavior and compatibility with Si complementary metal oxide semiconductor (CMOS processing. In this paper, we present a review of the recent progress in Ge-on-Si active photonics materials and devices for photon detection, modulation, and generation. We first discuss the band engineering of Ge using tensile strain, n-type doping, Sn alloying, and separate confinement of Γ vs. L electrons in quantum well (QW structures to transform the material towards a direct band gap semiconductor for enhancing optoelectronic properties. We then give a brief overview of epitaxial Ge-on-Si materials growth, followed by a summary of recent investigations towards low-temperature, direct growth of high crystallinity Ge and GeSn alloys on dielectric layers for 3D photonic integration. Finally, we review the most recent studies on waveguide-integrated Ge-on-Si photodetectors (PDs, electroabsorption modulators (EAMs, and laser diodes (LDs, and suggest possible future research directions for large-scale monolithic electronic-photonic integrated circuits on a Si platform.

  8. Next Generation, Si-Compatible Materials and Devices in the Si-Ge-Sn System

    Science.gov (United States)

    2015-10-09

    performed extensive growth studies aimed to create entire new families of Ge1-x-ySixSny materials on industrially compatible group IV platforms ( Si , Ge and...AFRL-AFOSR-VA-TR-2016-0044 Next generation, Si -compatible materials and devices in the Si -Ge-Sn system John Kouvetakis ARIZONA STATE UNIVERSITY Final...4. TITLE AND SUBTITLE Next generation, Si -compatible materials and devices in the Si -Ge-Sn system 5a. CONTRACT NUMBER FA9550-12-1-0208 5b. GRANT

  9. Deep levels, transport and THz emission properties of SiGe/Si quantum-well structures

    Institute of Scientific and Technical Information of China (English)

    I.; V.; ANTONOVA; M.; S.; KAGAN; E.; P.; NEUSTROEV; S.; A.; SMAGULOVA

    2009-01-01

    Recharging of quantum confinement levels in SiGe quantum wells (QW) was studied by charge deep-level transient spectroscopy (Q-DLTS) for Si/SiGe/Si structures with different Ge contents in the SiGe layer. A peak with activation energy varying in the range from 0 to 100 meV in different tempera-ture intervals was observed in Q-DLTS spectra. Activation energies extracted from Q-DLTS measure-mens are in good agreement with energies of quantum confinement levels in the QW.

  10. Study of a SiGeSn/GeSn/SiGeSn structure toward direct bandgap type-I quantum well for all group-IV optoelectronics.

    Science.gov (United States)

    Ghetmiri, Seyed Amir; Zhou, Yiyin; Margetis, Joe; Al-Kabi, Sattar; Dou, Wei; Mosleh, Aboozar; Du, Wei; Kuchuk, Andrian; Liu, Jifeng; Sun, Greg; Soref, Richard A; Tolle, John; Naseem, Hameed A; Li, Baohua; Mortazavi, Mansour; Yu, Shui-Qing

    2017-02-01

    A SiGeSn/GeSn/SiGeSn single quantum well structure was grown using an industry standard chemical vapor deposition reactor with low-cost commercially available precursors. The material characterization revealed the precisely controlled material growth process. Temperature-dependent photoluminescence spectra were correlated with band structure calculation for a structure accurately determined by high-resolution x-ray diffraction and transmission electron microscopy. Based on the result, a systematic study of SiGeSn and GeSn bandgap energy separation and barrier heights versus material compositions and strain was conducted, leading to a practical design of a type-I direct bandgap quantum well.

  11. Impacts of excimer laser annealing on Ge epilayer on Si

    Science.gov (United States)

    Huang, Zhiwei; Mao, Yichen; Yi, Xiaohui; Lin, Guangyang; Li, Cheng; Chen, Songyan; Huang, Wei; Wang, Jianyuan

    2017-02-01

    The impacts of excimer laser annealing on the crystallinity of Ge epilayers on Si substrate grown by low- and high-temperature two-step approach in an ultra-high vacuum chemical vapor deposition system were investigated. The samples were treated by excimer laser annealing (ELA) at various laser power densities with the temperature above the melting point of Ge, while below that of Si, resulting in effective reduction of point defects and dislocations in the Ge layer with smooth surface. The full-width at half-maximum (FWHM) of X-ray diffraction patterns of the low-temperature Ge epilayer decreases with the increase in laser power density, indicating the crystalline improvement and negligible effect of Ge-Si intermixing during ELA processes. The short laser pulse time and large cooling rate cause quick melting and recrystallization of Ge epilayer on Si in the non-thermal equilibrium process, rendering tensile strain in Ge epilayer as calculated quantitatively with thermal mismatch between Si and Ge. The FWHM of X-ray diffraction patterns is significantly reduced for the two-step grown samples after treated by a combination of ELA and conventional furnace thermal annealing, indicating that the crystalline of Ge epilayer is improved more effectively with pre- annealing by excimer laser.

  12. Si/SiGe/Si HBT直流特性的可靠性%Reliability of DC characteristics in mesa Si/SiGe/Si HBT

    Institute of Scientific and Technical Information of China (English)

    崔福现; 张万荣

    2003-01-01

    对单台面SiGe HBT在E-B结反偏应力下直流特性的可靠性进行了研究.研究结果表明,随应力时间的增加,开启电压增加,直流电流增益下降,特别是在低E-B正偏电压时下降明显;而交流电流增益退化缓慢.

  13. Carrier transport in Ge nanowires / Si substrate heterojunction

    Science.gov (United States)

    Lee, E.-K.; Kamenev, B.; Tsybeskov, L.; Sharma, S.; Kamins, T. I.

    2006-03-01

    Semiconductor nanowires (NWs) attached to lattice-mismatched single-crystal substrates form quasi-one-dimensional (QOD) heterojunctions (HJs) where efficient structural relaxation might occur due to high surface-to-volume ratio. Current-voltage characteristics in Ge NW/(p+)Si samples with nearly micron-long Ge NWs exhibit metal-type conductivity with ohmic behavior and little conductivity temperature dependence. In contrast, Ge NW/(n+)Si samples display significant change in conductivity as a function of temperature with an activation energy up to 200 meV. In a narrow temperature interval near 150 K we observed current instabilities and oscillations for Ge NW/(n+)Si. At higher temperatures we find negative differential photoconductivity at low forward biases. Our experimental results are explained using a model of nearly ideal Si substrate/Ge NW hetero-interfaces.

  14. High quality Ge epilayer on Si (1 0 0) with an ultrathin Si1-x Ge x /Si buffer layer by RPCVD

    Science.gov (United States)

    Chen, Da; Guo, Qinglei; Zhang, Nan; Xu, Anli; Wang, Bei; Li, Ya; Wang, Gang

    2017-07-01

    The authors report a method to grow high quality strain-relaxed Ge epilayer on a combination of low temperature Ge seed layer and Si1-x Ge x /Si superlattice buffer layer by reduced pressure chemical vapor deposition system without any subsequent annealing treatment. Prior to the growth of high quality Ge epilayer, an ultrathin Si1-x Ge x /Si superlattice buffer layer with the thickness of 50 nm and a 460 nm Ge seed layer were deposited successively at low temperature. Then an 840 nm Ge epilayer was grown at high deposition rate with the surface root-mean-square roughness of 0.707 nm and threading dislocation density of 2.5  ×  106 cm-2, respectively. Detailed investigations of the influence of ultrathin low-temperature Si1-x Ge x /Si superlattice buffer layer on the quality of Ge epilayer were performed, which indicates that the crystalline quality of Ge epilayer can be significantly improved by enhancing the Ge concentration of Si1-x Ge x /Si superlattice buffer layer.

  15. The effect of biaxial strain on impurity diffusion in Si and SiGe

    DEFF Research Database (Denmark)

    Larsen, Arne Nylandsted; Zangenberg, Nikolaj; Fage-Pedersen, Jacob

    2005-01-01

    Results from diffusion studies of different impurities in biaxially strained Si and Si"1"-"xGe"x for low x-values will be presented. The structures are all molecular-beam epitaxy (MBE) grown on strain-relaxed Si"1"-"xGe"x layers, and the impurity profiles are introduced during growth. We have...

  16. Improvement on Frequency Performance of SOI SiGe HBT

    Institute of Scientific and Technical Information of China (English)

    DAI Guang-hao; WANG Sheng-rong; LI Wen-jie

    2006-01-01

    Based on the advantages of SOI technology,the frequency performance of SiGe HBT with SOI structure has been simulated. Compared with bulk SiGe HBT,the results show that the buried oxide layer(BOX) can reduce collector-base capacitance CCB with the maximum value 89.3%,substrate-base capacitance CSB with 94.6%,and the maximum oscillation frequency is improved by 2.7. The SOI structure improves the frequency performance of SiGe HBT,which is adaptable to high-speed and high power applications.

  17. Acheivement of Nano-Scale SiGe Layer with Discrete Ge Mole Fraction Profile Using Batch-Type HVCVD

    Institute of Scientific and Technical Information of China (English)

    Gon-sub Lee; Tae-hun Shim; Jea-gun Park

    2004-01-01

    The strained Si grown on the relaxed SiGe-on-insulator C-MOSFET's is a promising device for the future system LSI devices with the design rule of sub-micron. The achievement of the discrete Ge mole fraction in the SiGe layer is a key engineering in low-temperature SiGe epitaxial growth using HVCVD. The pre-flow of GeH4 gas enhanced the Ge mole fraction and SiGe layer thickness. In addition, the Ge mole fraction and SiGe layer thickness increases with the gas ratio of GeH4/SiH4 + GeH4, process temperature, and gas flow time. However, the haze was produced if the Ge mole fraction is above 22wt%. The discrete-like Ge mole fraction with 22 wt% in 10 nm SiGe layer was obtained by the pre-flow of GeH4 for 10 s, the mixture gas ratio of GeH4/SiH4 + GeH4 of 67%, and the gas flow time for 150 s at the process temperature of 550 C.

  18. Determination of Ge content in high concentration Ge-doped Czochralski Si single crystals by FTIR

    Institute of Scientific and Technical Information of China (English)

    JIANG Zhongwei; ZHANG Weilian; NIU Xinhuan

    2005-01-01

    SiGe single crystals with different Ge concentrations were measured by Fourier transform infrared (FTIR) spectroscopy at room temperature (RT) and 10 K. A new peak appears at the wave number of 710 cm-1 and the spectroscopy becomes clearer with an increase in Ge content. The absorption strength and wave sharp of the 710 cm-1 peak are independent of temperature. The relation of the absorption coefficient amax, the band width of half maximum (BWHM) W1/2 of the 710 cm-1 peak, and the Ge concentration is determined with the Ge content obtained by SEM-EDX. The conversion factor is k = 1.211 at 10 K. Therefore, the Ge content in high concentration Ge doped CZ-Si single crystals can be determined by FTIR.

  19. MnFe1-xTixP0.63Ge0.12Si0.25(x=0,0.01,0.02,0.03)系列化合物的磁热效应%Magnetocaloric Effect of MnFe1 -xTixP0.63Ge0.12Si0.25 (x =0, 0.01, 0.02, 0.03) Compounds

    Institute of Scientific and Technical Information of China (English)

    王冬梅; 松林; 王耀辉; 张伟; 耿遥祥; 特古斯

    2012-01-01

    通过X射线衍射分析(XRD)和振动磁强计(VSM)磁性测量,研究了替代元素Ti替代Fe元素含量的MnFe1-xTixP0.63Ge0.12Si0.25(x=0,0.01,0.02,0.03)系列化合物的物相结构与磁热效应的影响.结果表明:该系列化合物的结构为Fe2P型六角晶系结构,空间群为P62m.主相均为( Mn,Fe)2(P,Ge,Si),并含有少量的第二相(Mn,Fe)3Si相.随着Ti原子替代Fe原子的增加化合物的晶格常数a增大,晶格常数c略有减小,晶胞体积V基本保持不变.随着Ti含量增加居里温度(TC)减小,热滞△Thys的大小改进不太明显.MnFeP0.63Ge0.12Si0.25的TC为305 K,当外磁场变化为0~1.5T时最大磁熵变的绝对值为14.8 J·(kg·K)-1.%The substitution effect of Ti for Fe on the structure and magnetoealoric properties in the MnFe1-xTixP0.63Ge0.12Si0.25(x= 0, 0.01, 0.02, 0.03) compounds was investigated by means of X-ray diffraction (XRD) and magnetic measurements. Analysis showed that the MnFe1-xTixP0.63Ge0.12Si0.25(x= 0, 0. 01, 0. 02, 0. 03) compounds mainly crystallized in the Fe2P-type hexagonal structure, and a small second phase of ( Mn,Fe)3Si was detected in all compounds. It was found that the lattice parameter a increased and the lattice parameter c slightly decreased with increasing x, and the unit cell volume did not obviously change. The Curie temperature decreased with the increase of Ti content and thermal hysteresis did not obviously change. Curie temperature of MnFeP0.63Ge0.12 Si0.25 was 305 K and the maximum magnetic entropy was 14. 8 J·( kg·K)-1 for a field change from 0 to 1.5 T.

  20. High Temperature Stable Nanocrystalline SiGe Thermoelectric Material

    Science.gov (United States)

    Yang, Sherwin (Inventor); Matejczyk, Daniel Edward (Inventor); Determan, William (Inventor)

    2013-01-01

    A method of forming a nanocomposite thermoelectric material having microstructural stability at temperatures greater than 1000 C. The method includes creating nanocrystalline powder by cryomilling. The method is particularly useful in forming SiGe alloy powder.

  1. Si-Ge-metal ternary phase diagram calculations

    Science.gov (United States)

    Fleurial, J. P.; Borshchevsky, A.

    1990-01-01

    Solution crystal growth and doping conditions of Si-Ge alloys used for high-temperature thermoelectric generation are determined here. Liquid-phase epitaxy (LPE) has been successfully employed recently to obtain single-crystalline homogeneous layers of Si-Ge solid solutions from a liquid metal solvent. Knowledge of Si-Ge-metallic solvent ternary phase diagrams is essential for further single-crystal growth development. Consequently, a thermodynamic equilibrium model was used to calculate the phase diagrams of the Si-Ge-M systems, including solid solubilities, where M is Al, Ga, In, Sn, Pb, Sb, or Bi. Good agreement between calculated liquidus and solidus data and experimental DTA and microprobe results was obtained. The results are used to compare the suitability of the different systems for crystal growth (by LPE-type process).

  2. Laser ablation and growth of Si and Ge

    Energy Technology Data Exchange (ETDEWEB)

    Yap, Seong Shan, E-mail: seong.yap@ntnu.no [Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Siew, Wee Ong; Nee, Chen Hon [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia); Reenaas, Turid Worren [Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Tou, Teck Yong [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia)

    2012-02-01

    In this work, we investigated the laser ablation and deposition of Si and Ge at room temperature in vacuum by employing nanosecond lasers of 248 nm, 355 nm, 532 nm and 1064 nm. Time-integrated optical emission spectra were obtained for neutrals and ionized Ge and Si species in the plasma at laser fluences from 0.5 to 11 J/cm{sup 2}. The deposited films were characterized by using Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Amorphous Si and Ge films, micron-sized crystalline droplets and nano-sized particles were deposited. The results suggested that ionized species in the plasma promote the process of subsurface implantation for both Si and Ge films while large droplets were produced from the superheated and melted layer of the target. The dependence of the properties of the materials on laser wavelength and fluence were discussed.

  3. 193 nm Excimer laser processing of Si/Ge/Si(100) micropatterns

    Science.gov (United States)

    Gontad, F.; Conde, J. C.; Chiussi, S.; Serra, C.; González, P.

    2016-01-01

    193 nm Excimer laser assisted growth and crystallization of amorphous Si/Ge bilayer patterns with circular structures of 3 μm diameter and around 25 nm total thickness, is presented. Amorphous patterns were grown by Laser induced Chemical Vapor Deposition, using nanostencils as shadow masks and then irradiated with the same laser to induce structural and compositional modifications for producing crystalline SiGe alloys through fast melting/solidification cycles. Compositional and structural analyses demonstrated that pulses of 240 mJ/cm2 lead to graded SiGe alloys with Si rich discs of 2 μm diameter on top, a buried Ge layer, and Ge rich SiGe rings surrounding each feature, as predicted by previous numerical simulation.

  4. Photoluminescence quenching effect by Si cap in n+ Ge on Si

    Science.gov (United States)

    Pan, H.; Takahashi, R.; Takinai, K.; Wada, K.

    2015-02-01

    Monolithically integrated Ge lasers on Si have long been one of the biggest challenges for electronic and photonic integration on Si Complementary Metal Oxide Semiconductor (CMOS) platform. The "last one mile" is to reduce the threshold current of the electrically pumped Ge-on-Si laser. We have studied the growth of heavily doped n type (n+) Ge and analyzed its photoluminescence (PL) characteristics of Ge with a Si cap and thermal oxide layers. It is found that the PL intensity of n+ Ge was significantly reduced by the cap and etching off the cap showed a ~100% recovery to the intensity of n+ Ge without the cap. Thermally oxidized n+ Ge, on the other hand, showed a ~50% increase in the PL intensity of uncapped n+ Ge. These finding indicated that capping of n+ Ge introduces non-radiative recombination centers due to defects (dislocations) to reduce the PL intensity, while oxidation passivates surface defects remained even on uncapped n+ Ge. Considering these, we have designed and fabricated an electrically pumped n+ Ge light emitting diode with no Si cap layer but oxidation. A broad luminescence of Ge at 1500-1700 nm has been demonstrated but yet lasing not observed.

  5. Optical phonons in Ge quantum dots obtained on Si(111)

    CERN Document Server

    Talochkin, A B

    2002-01-01

    The light combination scattering on the optical phonons in the Ge quantum dots, obtained on the Si surface of the (111) orientation through the molecular-beam epitaxy, is studied. The series of lines, connected with the phonon spectrum quantization, was observed. It is shown, that the phonon modes frequencies are well described by the elastic properties and dispersion of the voluminous Ge optical phonons. The value of the Ge quantum dots deformation is determined

  6. Optimization of Waveguide Structure for Tunable Optical Switch in Si/SiGe System

    Institute of Scientific and Technical Information of China (English)

    Seongjae Boo; Won-Taek Han

    2003-01-01

    A new electro-optical device using Si/SiGe-system with two parallel ridge waveguides is proposed for optical switching and the optimization of the structure for a single mode operation is investigated.

  7. Early effect of SiGe heterojunction bipolar transistors

    Science.gov (United States)

    Xu, Xiao-Bo; Zhang, He-Ming; Hu, Hui-Yong; Qu, Jiang-Tao

    2012-06-01

    The standard Early voltage of the SGP model is generalized for SiGe NPN heterojunction bipolar transistors (HBTs). A new compact formulation of the Early voltage compatible with the SGP model is presented. The impact of the Ge profile on Early effect is shown and validated by experiments. The model can be applied to the SGP model for circuit simulation.

  8. Properties of Si{sub n}, Ge{sub n}, and Si{sub n}Ge{sub n} clusters

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Yi; Rehman, Habib ur; Springborg, Michael [Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrücken (Germany)

    2015-01-22

    The structures of Si{sub n}, Ge{sub n}, and Si{sub n}Ge{sub n} clusters with up to 44 atoms have been determined theoretically using an unbiased structure-optimization method in combination with a parametrized, density-functional description of the total energy for a given structure. By analyzing the total energy in detail, particularly stable clusters are identified. Moreover, general trends in the structures are identified with the help of specifically constructed descriptors.

  9. Quantum Confinement Effects in Strained SiGe/Si Multiple Quantum Wells

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Strained SiGe/Si multiple quantum wells (MQWs) were grown by cold-wall ultrahigh vacuum chemical vapor deposition (UHV/CVD). Photoluminescence measurement was performed to study the exciton energies of strained Si0.84 Ge0.16/Si MQWs with SiGe well widths ranging from 4.2nm to 25.4nm. The confinement energy of 43meV is found in the Si0.84Ge0.16/Si MQWs with well width of 4.2nm. The confinement energy was calculated by solving the problem of a particle confined in a single finite rectangular poteintial well using one band effect mass model. Experimental and theoretical confinement energies are in good agreement

  10. Ge nanocrystals embedded in ultrathin Si3N4 multilayers with SiO2 barriers

    Science.gov (United States)

    Bahariqushchi, R.; Gundogdu, Sinan; Aydinli, A.

    2017-04-01

    Multilayers of germanium nanocrystals (NCs) embedded in thin films of silicon nitride matrix separated with SiO2 barriers have been fabricated using plasma enhanced chemical vapor deposition (PECVD). SiGeN/SiO2 alternating bilayers have been grown on quartz and Si substrates followed by post annealing in Ar ambient from 600 to 900 °C. High resolution transmission electron microscopy (HRTEM) as well as Raman spectroscopy show good crystallinity of Ge confined to SiGeN layers in samples annealed at 900 °C. Strong compressive stress for SiGeN/SiO2 structures were observed through Raman spectroscopy. Size, as well as NC-NC distance were controlled along the growth direction for multilayer samples by varying the thickness of bilayers. Visible photoluminescence (PL) at 2.3 and 3.1 eV with NC size dependent intensity is observed and possible origin of PL is discussed.

  11. Hydrostatic strain enhancement in laterally confined SiGe nanostripes

    Science.gov (United States)

    Vanacore, G. M.; Chaigneau, M.; Barrett, N.; Bollani, M.; Boioli, F.; Salvalaglio, M.; Montalenti, F.; Manini, N.; Caramella, L.; Biagioni, P.; Chrastina, D.; Isella, G.; Renault, O.; Zani, M.; Sordan, R.; Onida, G.; Ossikovski, R.; Drouhin, H.-J.; Tagliaferri, A.

    2013-09-01

    Strain engineering in SiGe nanostructures is fundamental for the design of optoelectronic devices at the nanoscale. Here we explore a new strategy, where SiGe structures are laterally confined by the Si substrate, to obtain high tensile strain yet avoid the use of external stressors, thus improving the scalability. Spectromicroscopy techniques, finite element method simulations, and ab initio calculations are used to investigate the strain state of laterally confined Ge-rich SiGe nanostripes. Strain information is obtained by tip-enhanced Raman spectroscopy with an unprecedented lateral resolution of ˜30 nm. The nanostripes exhibit a large tensile hydrostatic strain component, which is maximal at the center of the top free surface and becomes very small at the edges. The maximum lattice deformation is larger than the typical values of thermally relaxed Ge/Si(001) layers. This strain enhancement originates from a frustrated relaxation in the out-of-plane direction, resulting from the combination of the lateral confinement induced by the substrate side walls and the plastic relaxation of the misfit strain in the (001) plane at the SiGe/Si interface. The effect of this tensile lattice deformation at the stripe surface is probed by work function mapping, which is performed with a spatial resolution better than 100 nm using x-ray photoelectron emission microscopy. The nanostripes exhibit a positive work function shift with respect to a bulk SiGe alloy, quantitatively confirmed by electronic structure calculations of tensile-strained configurations. The present results have a potential impact on the design of optoelectronic devices at a nanometer-length scale.

  12. Fabrication and evaluation of propagation loss of Si/SiGe/Si photonic-wire waveguides for Si based optical modulator

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Younghyun, E-mail: yhkim@mosfet.t.u-tokyo.ac.jp [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Takenaka, Mitsuru [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Osada, Takenori; Hata, Masahiko [Sumitomo Chemical Co. Ltd., 6 Kitahara, Tsukuba, Ibaraki 300-3294 (Japan); Takagi, Shinichi [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2014-04-30

    We have characterized photonic-wire waveguides with Si/SiGe/Si heterostructure ribs for Si-based optical modulators. The Si (80 nm)/Si{sub 0.72}Ge{sub 0.28} (40 nm) layers grown on Si-on-insulator by molecular beam epitaxy for optical modulators were evaluated by in-situ reflection high-energy electron diffraction, atomic force microscope, X-ray diffraction and Raman spectroscopy, exhibiting that the fully-strained highly-crystalline SiGe layer was obtained. We have evaluated the propagation loss of the Si/strained SiGe/Si photonic-wire waveguides. The wavelength dependence of the propagation loss exhibits the bandgap narrowing of the strained Si{sub 0.72}Ge{sub 0.28}, while the optical absorption of the strained Si{sub 0.72}Ge{sub 0.28} is not significant for the optical modulator application at 1.55-μm wavelength. - Highlights: • We have characterized photonic-wire waveguides with Si/SiGe/Si heterostructure ribs. • The Si/Si{sub 0.72}Ge{sub 0.28} grown on Si-on-insulator were evaluated to be fully strained. • We have fabricated and evaluated the Si/strained SiGe/Si photonic-wire waveguides. • The wavelength dependence exhibits bandgap narrowing of the strained Si{sub 0.72}Ge{sub 0.28}. • Optical absorption of the SiGe is not significant for optical modulators at 1.55 μm.

  13. Fabrication and measurement of devices in Si/SiGe nanomembranes

    Science.gov (United States)

    Mohr, Robert

    Silicon/silicon-germanium (Si/SiGe) heterostructures are useful as hosts for gated quantum dots. The quality of the as-grown Si/SiGe heterostructure has a large impact on the final quality of the quantum dot as a qubit host. For many years, quantum dots have been fab- ricated on strain-graded heterostructures. Commonly used strain-graded heterostructures inevitably develop plastic defects that lead to interface roughness, crosshatch, and mosaic tilt. All of these factors are sources of disorder in Si/SiGe quantum electronics. In this dissertation, I report the fabrication of Hall bars and gated quantum dots on heterostructures grown on fully elastically relaxed SiGe nanomembranes, rather than strain-graded heterostructures. I report measurements of Hall bars demonstrating the creation of two-dimensional electron gases in these structures. I report the fabrication procedures used to create pairs of Hall bars and quantum dots on individual membranes. In addition, I explain a general process flow for the creation of Si/SiGe quantum devices. I focus especially on an ion-implantation technique I implemented for the fabrication of Hall bars and quantum dots in Si/SiGe heterostructures without modulation doping layers.

  14. Ge-Photodetectors for Si-Based Optoelectronic Integration

    Directory of Open Access Journals (Sweden)

    Sungjoo Lee

    2011-01-01

    Full Text Available High speed photodetectors are a key building block, which allow a large wavelength range of detection from 850 nm to telecommunication standards at optical fiber band passes of 1.3–1.55 µm. Such devices are key components in several applications such as local area networks, board to board, chip to chip and intrachip interconnects. Recent technological achievements in growth of high quality SiGe/Ge films on Si wafers have opened up the possibility of low cost Ge-based photodetectors for near infrared communication bands and high resolution spectral imaging with high quantum efficiencies. In this review article, the recent progress in the development and integration of Ge-photodetectors on Si-based photonics will be comprehensively reviewed, along with remaining technological issues to be overcome and future research trends.

  15. Nanoscale elemental quantification in heterostructured SiGe nanowires.

    Science.gov (United States)

    Hourani, W; Periwal, P; Bassani, F; Baron, T; Patriarche, G; Martinez, E

    2015-05-14

    The nanoscale chemical characterization of axial heterostructured Si1-xGex nanowires (NWs) has been performed using scanning Auger microscopy (SAM) through local spectroscopy, line-scan and depth profile measurements. Local Auger profiles are realized with sufficient lateral resolution to resolve individual nanowires. Axial and radial composition heterogeneities are highlighted. Our results confirm the phenomenon of Ge radial growth forming a Ge shell around the nanowire. Moreover, quantification is performed after verifying the absence of preferential sputtering of Si or Ge on a bulk SiGe sample. Hence, reliable results are obtained for heterostructured NW diameters higher than 100 nm. However, for smaller sizes, we have noticed that the sensitivity factors evaluated from bulk samples cannot be used because of edge effects occurring for highly topographical features and a modified contribution of backscattered electrons.

  16. Ge/GeSn heterostructures grown on Si (100) by molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Sadofyev, Yu. G., E-mail: sadofyev@hotmail.com; Martovitsky, V. P.; Bazalevsky, M. A.; Klekovkin, A. V. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Averyanov, D. V.; Vasil’evskii, I. S. [National Research Nuclear University MEPhI (Russian Federation)

    2015-01-15

    The growth of GeSn layers by molecular-beam epitaxy on Si (100) wafers coated with a germanium buffer layer is investigated. The properties of the fabricated structures are controlled by reflection high-energy electron diffraction, atomic-force microscopy, X-ray diffractometry, Rutherford backscattering, and Raman scattering. It is shown that GeSn layers with thicknesses up to 0.5 μm and Sn molar fractions up to 0.073 manifest no sign of plastic relaxation upon epitaxy. The lattice constant of the GeSn layers within the growth plane is precisely the same as that of Ge. The effect of rapid thermal annealing on the conversion of metastable elastically strained GeSn layers into a plastically relaxed state is examined. Ge/GeSn quantum wells with Sn molar fraction up to 0.11 are obtained.

  17. Poly-SiGe for MEMS-above-CMOS sensors

    CERN Document Server

    Gonzalez Ruiz, Pilar; Witvrouw, Ann

    2014-01-01

    Polycrystalline SiGe has emerged as a promising MEMS (Microelectromechanical Systems) structural material since it provides the desired mechanical properties at lower temperatures compared to poly-Si, allowing the direct post-processing on top of CMOS. This CMOS-MEMS monolithic integration can lead to more compact MEMS with improved performance. The potential of poly-SiGe for MEMS above-aluminum-backend CMOS integration has already been demonstrated. However, aggressive interconnect scaling has led to the replacement of the traditional aluminum metallization by copper (Cu) metallization, due to its lower resistivity and improved reliability. Poly-SiGe for MEMS-above-CMOS sensors demonstrates the compatibility of poly-SiGe with post-processing above the advanced CMOS technology nodes through the successful fabrication of an integrated poly-SiGe piezoresistive pressure sensor, directly fabricated above 0.13 m Cu-backend CMOS. Furthermore, this book presents the first detailed investigation on the influence o...

  18. Ge-on-Si laser operating at room temperature.

    Science.gov (United States)

    Liu, Jifeng; Sun, Xiaochen; Camacho-Aguilera, Rodolfo; Kimerling, Lionel C; Michel, Jurgen

    2010-03-01

    Monolithic lasers on Si are ideal for high-volume and large-scale electronic-photonic integration. Ge is an interesting candidate owing to its pseudodirect gap properties and compatibility with Si complementary metal oxide semiconductor technology. Recently we have demonstrated room-temperature photoluminescence, electroluminescence, and optical gain from the direct gap transition of band-engineered Ge-on-Si using tensile strain and n-type doping. Here we report what we believe to be the first experimental observation of lasing from the direct gap transition of Ge-on-Si at room temperature using an edge-emitting waveguide device. The emission exhibited a gain spectrum of 1590-1610 nm, line narrowing and polarization evolution from a mixed TE/TM to predominantly TE with increasing gain, and a clear threshold behavior.

  19. SiGe HBTs Optimization for Wireless Power Amplifier Applications

    Directory of Open Access Journals (Sweden)

    Pierre-Marie Mans

    2010-01-01

    Full Text Available This paper deals with SiGe HBTs optimization for power amplifier applications dedicated to wireless communications. In this work, we investigate the fT-BVCEO tradeoff by various collector optimization schemes such as epilayer thickness and dopant concentration, and SIC and CAP characteristics. Furthermore, a new trapezoidal base Germanium (Ge profile is proposed. Thanks to this profile, precise control of Ge content at the metallurgical emitter-base junction is obtained. Gain stability is obtained for a wide range of temperatures through tuning the emitter-base junction Ge percent. Finally, a comprehensive investigation of Ge introduction into the collector (backside Ge profile is conducted in order to improve the fT values at high injection levels.

  20. TEM studies of Ge nanocrystal formation in PECVD grown SiO2:Ge/SiO2 multilayers

    Science.gov (United States)

    Agan, S.; Dana, A.; Aydinli, A.

    2006-06-01

    We investigate the effect of annealing on the Ge nanocrystal formation in multilayered germanosilicate-oxide films grown on Si substrates by plasma enhanced chemical vapour deposition (PECVD). The multilayered samples were annealed at temperatures ranging from 750 to 900 °C for 5 min under nitrogen atmosphere. The onset of formation of Ge nanocrystals, at 750 °C, can be observed via high resolution TEM micrographs. The diameters of Ge nanocrystals were observed to be between 5 and 14 nm. As the annealing temperature is raised to 850 °C, a second layer of Ge nanocrystals forms next to the original precipitation band, positioning itself closer to the substrate SiO2 interface. High resolution cross section TEM images, electron diffraction and electron energy-loss spectroscopy as well as energy-dispersive x-ray analysis (EDAX) data all indicate that Ge nanocrystals are present in each layer.

  1. Experiments and Modeling of Si-Ge Interdiffusion with Partial Strain Relaxation in Epitaxial SiGe Heterostructures

    KAUST Repository

    Dong, Y.

    2014-07-26

    Si-Ge interdiffusion and strain relaxation were studied in a metastable SiGe epitaxial structure. With Ge concentration profiling and ex-situ strain analysis, it was shown that during thermal anneals, both Si-Ge interdiffusion and strain relaxation occurred. Furthermore, the time evolutions of both strain relaxation and interdiffusion were characterized. It showed that during the ramp-up stage of thermal anneals at higher temperatures (800°C and 840°C), the degree of relaxation, R, reached a “plateau”, while interdiffusion was negligible. With the approximation that the R value is constant after the ramp-up stage, a quantitative interdiffusivity model was built to account for both the effect of strain relaxation and the impact of the relaxation induced dislocations, which gave good agreement with the experiment data.

  2. Tensile-strained Ge/SiGe quantum-well photodetectors on silicon substrates with extended infrared response.

    Science.gov (United States)

    Chang, Guo-En; Chen, Shao-Wei; Cheng, H H

    2016-08-08

    We report on tensile-strained Ge/Si0.11Ge0.89 quantum-well (QW) metal-semiconductor-metal (MSM) photodetectors on Si substrates. A tensile strain of 0.21% is introduced into the Ge wells by growing the QW stack on in-situ annealed Ge-on-Si virtual substrates (VS). The optical characterization of Ge/Si0.11Ge0.89 QW MSM photodetectors indicates that the optical response increases to a wavelength of 1.5 μm or higher owing to the strain-induced direct bandgap shrinkage. Analysis of the band structure by using a k · p model suggests that by optimizing the tensile strain and Ge well width, tensile-strained Ge/SiGe QW photodetectors can be designed to cover the telecommunication C-band and beyond for optical telecommunications and on-chip interconnection.

  3. Ion beam synthesis of SiGe alloy layers

    Energy Technology Data Exchange (ETDEWEB)

    Im, Seongil [Univ. of California, Berkeley, CA (United States)

    1994-05-01

    Procedures required for minimizing structural defects generated during ion beam synthesis of SiGe alloy layers were studied. Synthesis of 200 mm SiGe alloy layers by implantation of 120-keV Ge ions into <100> oriented Si wafers yielded various Ge peak concentrations after the following doses, 2 x 1016cm-2, 3 x 1016cm-2 (mid), and 5 x 1016cm-2 (high). Following implantation, solid phase epitaxial (SPE) annealing in ambient N2 at 800C for 1 hr. resulted in only slight redistribution of the Ge. Two kinds of extended defects were observed in alloy layers over 3 x l016cm-2cm dose at room temperature (RT): end-of-range (EOR) dislocation loops and strain-induced stacking faults. Density of EOR dislocation loops was much lower in alloys produced by 77K implantation than by RT implantation. Decreasing the dose to obtain 5 at% peak Ge concentration prevents strain relaxation, while those SPE layers with more than 7 at% Ge peak show high densities of misfit- induced stacking faults. Sequential implantation of C following high dose Ge implantation (12 at% Ge peak concentration in layer) brought about a remarkable decrease in density of misfit-induced stacking faults. For peak implanted C > 0.55 at%, stacking fault generation in the epitaxial layer was suppressed, owing to strain compensation by C atoms in the SiGe lattice. A SiGe alloy layer with 0.9 at% C peak concentration under a 12 at% Ge peak exhibited the best microstructure. Results indicate that optimum Ge/C ratio for strain compensation is between 11 and 22. The interface between amorphous and regrown phases (a/c interface) had a dramatic morphology change during its migration to the surface. Initial <100> planar interface decomposes into a <111> faceted interface, changing the growth kinetics; this is associated with strain relaxation by stacking fault formation on (111) planes in the a/c interface.

  4. Nanoengineering of an Si/MnGe quantum dot superlattice for high Curie-temperature ferromagnetism.

    Science.gov (United States)

    Nie, Tianxiao; Kou, Xufeng; Tang, Jianshi; Fan, Yabin; Lee, Shengwei; He, Qinglin; Chang, Li-Te; Murata, Koichi; Gen, Yin; Wang, Kang L

    2017-02-14

    The realization and application of spintronic devices would be dramatically advanced if room-temperature ferromagnetism could be integrated into semiconductor nanostructures, especially when compatible with mature silicon technology. Herein, we report the observation of such a system - an Si/MnGe superlattice with quantum dots well aligned in the vertical direction successfully grown by molecular beam epitaxy. Such a unique system could take full advantage of the type-II energy band structure of the Si/Ge heterostructure, which could trap the holes inside MnGe QDs, significantly enhancing the hole-mediated ferromagnetism. Magnetic measurements indeed found that the superlattice structure exhibited a Curie temperature of above 400 K. Furthermore, zero-field cooling and field cooling curves could confirm the absence of ferromagnetic compounds, such as Ge8Mn11 (Tc ∼ 270 K) and Ge3Mn5 (Tc ∼ 296 K) in our system. Magnetotransport measurement revealed a clear magnetoresistance transition from negative to positive and a pronounced anomalous Hall effect. Such a unique Si/MnGe superlattice sets a new stage for strengthening ferromagnetism due to the enhanced hole-mediation by quantum confinement, which can be exploited for realizing the room-temperature Ge-based spin field-effect transistors in the future.

  5. Si/SiGe heterointerfaces in one-, two-, and three-dimensional nanostructures: their impact on SiGe light emission

    Science.gov (United States)

    Lockwood, David; Wu, Xiaohua; Baribeau, Jean-Marc; Mala, Selina; Wang, Xialou; Tsybeskov, Leonid

    2016-03-01

    Fast optical interconnects together with an associated light emitter that are both compatible with conventional Si-based complementary metal-oxide- semiconductor (CMOS) integrated circuit technology is an unavoidable requirement for the next-generation microprocessors and computers. Self-assembled Si/Si1-xGex nanostructures, which can emit light at wavelengths within the important optical communication wavelength range of 1.3 - 1.55 μm, are already compatible with standard CMOS practices. However, the expected long carrier radiative lifetimes observed to date in Si and Si/Si1-xGex nanostructures have prevented the attainment of efficient light-emitting devices including the desired lasers. Thus, the engineering of Si/Si1-xGex heterostructures having a controlled composition and sharp interfaces is crucial for producing the requisite fast and efficient photoluminescence (PL) at energies in the range 0.8-0.9 eV. In this paper we assess how the nature of the interfaces between SiGe nanostructures and Si in heterostructures strongly affects carrier mobility and recombination for physical confinement in three dimensions (corresponding to the case of quantum dots), two dimensions (corresponding to quantum wires), and one dimension (corresponding to quantum wells). The interface sharpness is influenced by many factors such as growth conditions, strain, and thermal processing, which in practice can make it difficult to attain the ideal structures required. This is certainly the case for nanostructure confinement in one dimension. However, we demonstrate that axial Si/Ge nanowire (NW) heterojunctions (HJs) with a Si/Ge NW diameter in the range 50 - 120 nm produce a clear PL signal associated with band-to-band electron-hole recombination at the NW HJ that is attributed to a specific interfacial SiGe alloy composition. For three-dimensional confinement, the experiments outlined here show that two quite different Si1-xGex nanostructures incorporated into a Si0.6Ge0.4 wavy

  6. Si/SiGe heterointerfaces in one-, two-, and three-dimensional nanostructures: their impact on SiGe light emission

    Directory of Open Access Journals (Sweden)

    David J. Lockwood

    2016-03-01

    Full Text Available Fast optical interconnects together with an associated light emitter that are both compatible with conventional Si-based complementary metal-oxide- semiconductor (CMOS integrated circuit technology is an unavoidable requirement for the next-generation microprocessors and computers. Self-assembled Si/Si1-xGex nanostructures, which can emit light at wavelengths within the important optical communication wavelength range of 1.3 – 1.55 μm, are already compatible with standard CMOS practices. However, the expected long carrier radiative lifetimes observed to date in Si and Si/Si1-xGex nanostructures have prevented the attainment of efficient light-emitting devices including the desired lasers. Thus, the engineering of Si/Si1-xGex heterostructures having a controlled composition and sharp interfaces is crucial for producing the requisite fast and efficient photoluminescence (PL at energies in the range 0.8-0.9 eV. In this paper we assess how the nature of the interfaces between SiGe nanostructures and Si in heterostructures strongly affects carrier mobility and recombination for physical confinement in three dimensions (corresponding to the case of quantum dots, two dimensions (corresponding to quantum wires, and one dimension (corresponding to quantum wells. The interface sharpness is influenced by many factors such as growth conditions, strain, and thermal processing, which in practice can make it difficult to attain the ideal structures required. This is certainly the case for nanostructure confinement in one dimension. However, we demonstrate that axial Si/Ge nanowire (NW heterojunctions (HJs with a Si/Ge NW diameter in the range 50 – 120 nm produce a clear PL signal associated with band-to-band electron-hole recombination at the NW HJ that is attributed to a specific interfacial SiGe alloy composition. For three-dimensional confinement, the experiments outlined here show that two quite different Si1-xGex nanostructures incorporated into a Si

  7. On the compliant behaviour of free-standing Si nanostructures on Si(001) for Ge nanoheteroepitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kozlowski, Grzegorz

    2012-04-24

    Selective chemical vapor deposition Ge heteroepitaxy approaches for high quality Ge nanostructure growth with reasonable thermal budget must be developed for local Ge photonic module integration. A promising vision is offered by the compliant substrate effects within nanometer scale Ge/Si heteroepitaxial structures. Here, in contrast to the classical Ge deposition on bulk Si substrates, the thermal and lattice mismatch strain energy accumulated in the Ge epilayer is partially shifted to the free-standing Si nanostructure. This strain partitioning phenomenon is at the very heart of the nanoheteroepitaxy theory (NHE) and, if strain energy levels are correctly balanced, offers the vision to grow defect-free nanostructures of lattice mismatched semiconductors on Si. In case of the Ge/Si heterosystem with a lattice mismatch of 4.2%, the strain partitioning phenomenon is expected to be triggered when free-standing Si nanopillars with the width of 50 nm and below are used. In order to experimentally verify NHE with its compliant substrate effects, a set of free-standing Ge/Si nanostructures with diameter ranging from 150 to 50 nm were fabricated and investigated. The main limitation corresponds to a simultaneous detection of (a) the strain partitioning phenomenon between Ge and Si and (b) the absence of defects on the nano-scale. In this respect, synchrotron-based grazing incidence X-ray diffraction was applied to study the epitaxial relationship, defect and strain characteristics with high resolution and sensitivity in a non-destructive way. Raman spectroscopy supported by finite element method calculations were used to investigate the strain distribution within a single Ge/Si nanostructure. Special focus was devoted to transmission electron microscopy to determine the quality of the Ge epilayer. It was found, that although high quality Ge nanoclusters can be achieved by thermal annealing on Si pillars bigger than 50 nm in width, no proof of strain partitioning

  8. Structure of compounds E(SnMe3)4 (E = Si, Ge) as seen by high-resolution X-ray powder diffraction and solid-state NMR.

    Science.gov (United States)

    Dinnebier, Robert E; Bernatowicz, Piotr; Helluy, Xavier; Sebald, Angelika; Wunschel, Markus; Fitch, Andy; van Smaalen, Sander

    2002-02-01

    The compounds tetrakis(trimethylstannyl)germane, Ge(SnMe3)4 (1), and tetrakis(trimethylstannyl)silane, Si(SnMe3)4 (2), have crystal structures with the quasispherical molecules in a closed-packed stacking. At room temperature both structures have the space group P1 (Z = 2) with a = 9.94457 (5), b = 14.52927 (8), c = 9.16021 (5) A, alpha = 90.53390 (30), beta = 111.73080 (30), gamma = 90.0049 (4) degrees, and V = 1229.414 (12) A3 for (1) and a = 9.92009 (7), b = 14.51029 (11), c = 9.13585 (7) A, alpha = 90.4769 (4), beta = 111.6724 (4), gamma = 89.9877 (6) degrees, and V = 1222.037 (16) A3 for (2). The molecules are found to be ordered as a result of steric interactions between neighboring molecules, as shown by analyzing the distances between the atoms. Upon heating, both compounds undergo a first-order phase transition at temperatures T(c) = 348 +/- 5 K, as characterized by a relative jump of the lattice parameter of approximately 16%. At 353 K, both structures have the space group P1 (Z = 4), with a = 14.2037 (2) A, and V = 2865.52 (7) A3 for (1) and a = 14.1346 (2) A, and V = 2823.90 (7) A3 for (2). Rietveld refinements were performed for the low-temperature phases measured at T = 295 K [R(wp) = 0.0844 for (1), R(wp) = 0.0940 for (2)] and for the high-temperature phases measured at T = 353 K [R(wp) = 0.0891 for (1), R(wp) = 0.0542 for (2)]. The combination of high-resolution X-ray powder diffraction measurements and variable-temperature magic-angle-spinning 13C, 29Si and 119Sn NMR experiments demonstrates low crystallographic and molecular (C1) symmetries for the low-temperature phases of (1) and (2) at temperatures T 348 +/- 5 K.

  9. Thermal oxidation of Ge-implanted Si: Role of defects

    Science.gov (United States)

    Dedyulin, S. N.; Goncharova, L. V.

    2012-02-01

    Thermal oxidation of Ge-implanted Si (SiGe) was carried out in dry O at 1073, 1173, and 1273 K for various times. Rutherford backscattering spectrometry in random and channeling geometry was used to characterize the SiO thickness and composition of the Si (dry oxidation) [3,4,8,9,13-17] or by bubbling N/O through HO (wet oxidation) [5-7,9-12,18]. In these studies SiGe thin films were obtained by different growth techniques such as chemical vapor deposition (CVD) [4-6,19,12], molecular beam epitaxy (MBE) [7,8,14,19,21-23], physical evaporation [3,18] as well as Ge ion implantation in Si [9-11,13,15-17]. Despite the great differences in the preparation of SiGe samples and oxidation procedures, the main features of SiGe thermal oxidation may be summarized by the following: Pure SiO was formed during oxidation: Ge atoms that were rejected from the growing silicon oxide piled up at the interface. This was observed in all cases, unless the temperature was low enough (⩽973 K)[24], or the oxidation pressure was high [6,19], or the Ge concentration, x, in the alloy satisfied x⩾0.5[7,8], or the oxidation time was very short [22,23]. All these conditions prevent Ge diffusion away from the reacting interface. The oxidation rate of SiGe in a wet atmosphere was enhanced in comparison to pure Si [4,5,9-12,18,25], while there was no enhancement in the dry O[9,16,22,25] (unless the sample was first pre-enriched with Ge to form approximately one monolayer of Ge at the interface [9]). Oxidation rate enhancement occurs during an initial linear regime of oxide growth [10]. SiGe oxidation rate enhancement has been explained by: (i) the weaker Si-Ge bond [11], (ii) Ge catalytic role for oxidation reaction [12], and (iii) changes in defect generation at the reacting interface [12]. It was shown for Ge ion implanted samples that the Deal and Grove model (DG model) for Si oxidation can still be applied with the linear B/ A constant modified to take into account enhanced oxidation

  10. Formation mechanisms of nano and microcones by laser radiation on surfaces of Si, Ge, and SiGe crystals.

    Science.gov (United States)

    Medvid, Artur; Onufrijevs, Pavels; Jarimaviciute-Gudaitiene, Renata; Dauksta, Edvins; Prosycevas, Igoris

    2013-06-04

    In this work we study the mechanisms of laser radiation interaction with elementary semiconductors such as Si and Ge and their solid solution SiGe. As a result of this investigation, the mechanisms of nanocones and microcones formation on a surface of semiconductor were proposed. We have shown the possibility to control the size and the shape of cones both by the laser. The main reason for the formation of nanocones is the mechanical compressive stresses due to the atoms' redistribution caused by the gradient of temperature induced by strongly absorbed laser radiation. According to our investigation, the nanocone formation mechanism in semiconductors is characterized by two stages. The first stage is characterized by formation of a p-n junction for elementary semiconductors or of a Ge/Si heterojunction for SiGe solid solution. The generation and redistribution of intrinsic point defects in elementary semiconductors and Ge atoms concentration on the irradiated surface of SiGe solid solution in temperature gradient field take place at this stage due to the thermogradient effect which is caused by strongly absorbed laser radiation. The second stage is characterized by formation of nanocones due to mechanical plastic deformation of the compressed Ge layer on Si. Moreover, a new 1D-graded band gap structure in elementary semiconductors due to quantum confinement effect was formed. For the formation of microcones Ni/Si structure was used. The mechanism of the formation of microcones is characterized by two stages as well. The first stage is the melting of Ni film after irradiation by laser beam and formation of Ni islands due to surface tension force. The second step is the melting of Ni and subsequent manifestations of Marangoni effect with the growth of microcones.

  11. Theoretical Investigations of Si-Ge Alloys in P42/ncm Phase: First-Principles Calculations

    Science.gov (United States)

    Ma, Zhenyang; Liu, Xuhong; Yu, Xinhai; Shi, Chunlei; Yan, Fang

    2017-01-01

    The structural, mechanical, anisotropic, electronic and thermal properties of Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase are investigated in this work. The calculations have been performed with an ultra-soft pseudopotential by using the generalized gradient approximation and local density approximation in the framework of density functional theory. The achieved results for the lattice constants and band gaps of P42/ncm-Si and P42/ncm-Ge in this research have good accordance with other results. The calculated elastic constants and elastic moduli of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase are better than that of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/mnm phase. The Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase exhibit varying degrees of mechanical anisotropic properties in Poisson’s ratio, shear modulus, Young’s modulus, and universal anisotropic index. The band structures of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase show that they are all indirect band gap semiconductors with band gap of 1.46 eV, 1.25 eV, 1.36 eV and 1.00 eV, respectively. In addition, we also found that the minimum thermal conductivity κmin of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase exhibit different degrees of anisotropic properties in (001), (010), (100) and (01¯0) planes. PMID:28772964

  12. Theoretical Investigations of Si-Ge Alloys in P42/ncm Phase: First-Principles Calculations

    Directory of Open Access Journals (Sweden)

    Zhenyang Ma

    2017-05-01

    Full Text Available The structural, mechanical, anisotropic, electronic and thermal properties of Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase are investigated in this work. The calculations have been performed with an ultra-soft pseudopotential by using the generalized gradient approximation and local density approximation in the framework of density functional theory. The achieved results for the lattice constants and band gaps of P42/ncm-Si and P42/ncm-Ge in this research have good accordance with other results. The calculated elastic constants and elastic moduli of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase are better than that of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/mnm phase. The Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase exhibit varying degrees of mechanical anisotropic properties in Poisson’s ratio, shear modulus, Young’s modulus, and universal anisotropic index. The band structures of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase show that they are all indirect band gap semiconductors with band gap of 1.46 eV, 1.25 eV, 1.36 eV and 1.00 eV, respectively. In addition, we also found that the minimum thermal conductivity κmin of the Si, Si0.667Ge0.333, Si0.333Ge0.667 and Ge in P42/ncm phase exhibit different degrees of anisotropic properties in (001, (010, (100 and (01¯0 planes.

  13. p-n Junction Diodes Fabricated on Si-Si/Ge Heteroepitaxial Films

    Science.gov (United States)

    Das, K.; Mazumder, M. D. A.; Hall, H.; Alterovitz, Samuel A. (Technical Monitor)

    2000-01-01

    A set of photolithographic masks was designed for the fabrication of diodes in the Si-Si/Ge material system. Fabrication was performed on samples obtained from two different wafers: (1) a complete HBT structure with an n (Si emitter), p (Si/Ge base), and an n/n+ (Si collector/sub-collector) deposited epitaxially (MBE) on a high resistivity p-Si substrate, (2) an HBT structure where epitaxial growth was terminated after the p-type base (Si/Ge) layer deposition. Two different process runs were attempted for the fabrication of Si-Si/Ge (n-p) and Si/Ge-Si (p-n) junction diodes formed between the emitter-base and base-collector layers, respectively, of the Si-Si/Ge-Si HBT structure. One of the processes employed a plasma etching step to expose the p-layer in the structure (1) and to expose the e-layer in structure (2). The Contact metallization used for these diodes was a Cu-based metallization scheme that was developed during the first year of the grant. The plasma-etched base-collector diodes on structure (2) exhibited well-behaved diode-like characteristics. However, the plasma-etched emitter-base diodes demonstrated back-to-back diode characteristics. These back-to back characteristics were probably due to complete etching of the base-layer, yielding a p-n-p diode. The deep implantation process yielded rectifying diodes with asymmetric forward and reverse characteristics. The ideality factor of these diodes were between 1.6 -2.1, indicating that the quality of the MBE grown epitaxial films was not sufficiently high, and also incomplete annealing of the implantation damage. Further study will be conducted on CVD grown films, which are expected to have higher epitaxial quality.

  14. Study on Gd-Si-Ge Alloys Using Domestic Gd

    Institute of Scientific and Technical Information of China (English)

    吴卫; 卢定伟

    2004-01-01

    To evaluate the possibility of using Gd-Si-Ge alloys in magnetic refrigerators,samples of Gd-Si-Ge alloys were made of domestic Gd.The magnetocaloric effect of samples was estimated by magnetic entropy change (-ΔSm) calculated from M-H curves according to Maxwell relation.The first order phase transformation was destroyed due to the impurities in the commercial Gd,so that no giant magnetocaloric effect was found.The samples made of purified Gd exhibit first order phase transformation,and the -ΔSm is basically consistent with the published data of Ames laboratory,USA.This work proves that Gd-Si-Ge alloys made of domestic Gd can be utilized in magnetic refrigerators.

  15. Low-temperature strain relaxation in SiGe/Si heterostructures implanted with Ge{sup +} ions

    Energy Technology Data Exchange (ETDEWEB)

    Avrutin, V.S.; Izyumskaya, N.F.; Vyatkin, A.F.; Zinenko, V.I.; Agafonov, Yu.A.; Irzhak, D.V.; Roshchupkin, D.V.; Steinman, E.A.; Vdovin, V.I.; Yugova, T.G

    2003-06-15

    Pseudomorphic Si{sub 0.76}Ge{sub 0.24}/Si heterostructures grown by molecular beam epitaxy were implanted with Ge{sup +} ions at 400 deg. C in such a way that an ion-damaged region was located below the SiGe/Si interface. The effect of Ge{sup +}-ion irradiation on strain-relaxation rate and defect structure in the heterostructures was studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and low-temperature photoluminescence (PL). It was found that annealing at a temperature as low as 600 deg. C resulted in very high degree of strain relaxation, while density of threading dislocations was low (<10{sup 5} cm{sup -2}). The enhanced strain relaxation was attributed to the fact that complexes of point defects produced by the heavy-ion implantation at the elevated temperature acted as nucleation sites for dislocations. The obtained results allowed us to propose a method for preparation of thin highly relaxed SiGe layer with low threading dislocation density and good surface morphology.

  16. Spin-polarized photoemission from SiGe heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, A.; Bottegoni, F.; Isella, G.; Cecchi, S.; Chrastina, D.; Finazzi, M.; Ciccacci, F. [LNESS-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2013-12-04

    We apply the principles of Optical Orientation to measure by Mott polarimetry the spin polarization of electrons photoemitted from different group-IV heterostructures. The maximum measured spin polarization, obtained from a Ge/Si{sub 0.31}Ge{sub 0.69} strained film, undoubtedly exceeds the maximum value of 50% attainable in bulk structures. The explanation we give for this result lies in the enhanced band orbital mixing between light hole and split-off valence bands as a consequence of the compressive strain experienced by the thin Ge layer.

  17. Photoluminescence of phosphorus atomic layer doped Ge grown on Si

    Science.gov (United States)

    Yamamoto, Yuji; Nien, Li-Wei; Capellini, Giovanni; Virgilio, Michele; Costina, Ioan; Schubert, Markus Andreas; Seifert, Winfried; Srinivasan, Ashwyn; Loo, Roger; Scappucci, Giordano; Sabbagh, Diego; Hesse, Anne; Murota, Junichi; Schroeder, Thomas; Tillack, Bernd

    2017-10-01

    Improvement of the photoluminescence (PL) of Phosphorus (P) doped Ge by P atomic layer doping (ALD) is investigated. Fifty P delta layers of 8 × 1013 cm‑2 separated by 4 nm Ge spacer are selectively deposited at 300 °C on a 700 nm thick P-doped Ge buffer layer of 1.4 × 1019 cm‑3 on SiO2 structured Si (100) substrate. A high P concentration region of 1.6 × 1020 cm‑3 with abrupt P delta profiles is formed by the P-ALD process. Compared to the P-doped Ge buffer layer, a reduced PL intensity is observed, which might be caused by a higher density of point defects in the P delta doped Ge layer. The peak position is shifted by ∼0.1 eV towards lower energy, indicating an increased active carrier concentration in the P-delta doped Ge layer. By introducing annealing at 400 °C to 500 °C after each Ge spacer deposition, P desorption and diffusion is observed resulting in relatively uniform P profiles of ∼2 × 1019 cm‑3. Increased PL intensity and red shift of the PL peak are observed due to improved crystallinity and higher active P concentration.

  18. Ternary and quaternary Ni(Si)Ge(Sn) contact formation for highly strained Ge p- and n-MOSFETs

    Science.gov (United States)

    Wirths, S.; Troitsch, R.; Mussler, G.; Hartmann, J.-M.; Zaumseil, P.; Schroeder, T.; Mantl, S.; Buca, D.

    2015-05-01

    The formation of new ternary NiGeSn and quaternary NiSiGeSn alloys has been investigated to fabricate metallic contacts on high Sn content, potentially direct bandgap group IV semiconductors. (Si)GeSn layers were pseudomorphically grown on Ge buffered Si(001) by reduced pressure chemical vapor deposition. Ni, i.e. the metal of choice for source/drain metallization in Si nanoelectronics, is employed for the stano-(silicon)-germanidation of highly strained (Si)GeSn alloys. We show that NiGeSn on GeSn layers change phase from well-oriented Ni5(GeSn)3 to poly-crystalline Ni1(GeSn)1 at very low annealing temperatures. A large range of GeSn compositions with Sn concentrations up to 12 at.%, and SiGeSn ternaries with large Si and Sn compositions from 18%/3% to 4%/11% are investigated. In addition, the sheet resistance, of importance for electronic or optoelectronic device contacts, is quantified. The incorporation of Si extends the thermal stability of the resulting low resistive quaternary phase compared to their NiGeSn counterparts.

  19. Substrate Effects in Wideband SiGe HBT Mixer Circuits

    DEFF Research Database (Denmark)

    Johansen, Tom Keinicke; Vidkjær, Jens; Krozer, Viktor

    2005-01-01

    In this paper, the influence from substrate effects on the performance of wideband SiGe HBT mixer circuits is investigated. Equivalent circuit models including substrate networks are extracted from on-wafer test structures and compared with electromagnetic simulations. Electromagnetic simulations...... are also applied to predict short distance substrate coupling effects. Simulation results using extracted equivalent circuit models and substrate coupling networks are compared with experimental results obtained on a wideband mixer circuit implemented in a 0.35 μm, 60 GHz ft SiGe HBT BiCMOS process....

  20. Experimental observation of motion of edge dislocations in Ge/Ge x Si1- x /Si(001) ( x = 0.2-0.6) heterostructures

    Science.gov (United States)

    Bolkhovityanov, Yu. B.; Gutakovskii, A. K.; Deryabin, A. S.; Sokolov, L. V.

    2016-11-01

    The Ge/Ge x Si1- x /Si(001) ( x = 0.2-0.6) heterostructures grown by the molecular epitaxy method are analyzed using high-resolution electron microscopy with atomic resolution. The thickness of the Ge x Si1- x buffer layer is 7-35 nm. It is shown that such heterostructures relax in two stages: an ordered network of edge dislocations is formed during their growth (500°C) at the Ge/GeSi interface and then, contrary to the generally accepted opinion concerning their immobility, some of the edge dislocations move through the buffer GeSi layer to the GeSi/Si(001) interface during annealing at higher temperatures and x > 0.3. It is found that plastic relaxation of the GeSi buffer layer occurs due to motion of dislocation complexes of the edge type, consisting of a pair of complementary 60° dislocations with the ends of {111} extra planes located approximately at a distance from 2 to 12 interplanar spacings. It is shown that the penetration of dislocation complexes into the GeSi buffer layer and further to the GeSi/Si interface is intensified with increasing annealing temperature (600-800°C) and the fraction of Ge in the buffer layer.

  1. Solid State Synthesis and Thermoelectric Properties of Mg-Si-Ge System

    Institute of Scientific and Technical Information of China (English)

    Renbo SONG; Yazheng LIU; Tatsuhiko AIZAWA

    2005-01-01

    Thermoelectric materials, Mg2Si1-xGex (x=0, 0.2, 0.4, 0.6, 0.8, 1), have been prepared by bulk mechanical alloying (BMA) and hot pressing (HP). The electrical conductivity, Seebeck coefficient and thermal conductivity were measured from room temperature up to about 700 K. The electrical conductivity of all the samples increases with increasing temperature, while the Seebeck coefficient and thermal conductivity decrease with increasing temperature.Mg2Si and Mg2Si0.8Ge0.2 possess negative type of conductivity, while for other compounds it is positive. At the same time, the effect of hot processing condition on thermoelectric properties was also investigated. The maximum figure of merit of Mg2Si0.6Ge0.4 was obtained with the processing parameter of BMA at 600 cycles and hot pressing at 773 K and 1 GPa for 1 h.

  2. Development of an improved performance SiGe unicouple

    Science.gov (United States)

    Nakahara, Jan F.; Franklin, Brian; DeFillipo, Lawrence E.

    1995-01-01

    This paper describes the fabrication of unicouples with improved SiGe alloys. Based on laboratory measurements of the thermoelectric properties the improved materials provide about a 10% improvement in the figure-of-merit between 573 and 1273 K compared to standard coarse grain unicouple materials. The improved materials are p-type Si0.796Ge0.199B0.005 fabricated at Martin Marietta Astro Space by the Vacuum casting/hot pressing method and n-type Si0.784Ge0.196Ga0.005P0.015 fabricated at Ames Laboratory by the mechanical alloying/hot isostatic pressing method. The standard unicouple bonding process was adjusted to accommodate the lower melting temperature of the SiGe/GaP material. A two-step diffusion bonding process was developed such that the p-type material is bonded to the SiMo hot shoe first at 1594 K followed by the lower melting point n-type material between 1518 and 1520 K. Standard procedures were used to silicon nitride coat the thermoelectric pellets and to attach the cold side CTE transition and heat rejection components to produce unicouples. Two unicouples successfully withstood simulated rivet operations as would be experienced in the fabrication of a Radioisotope Thermoelectric Generator (RTG) converter to verify the integrity of the tungsten cold shoe to thermoelectric material interface. The performance of these unicouples will be further evaluated in an 18-couple test module.

  3. Phase Competitions behind the Giant Magnetic Entropy Variation: Gd5Si2Ge2 and Tb5Si2Ge2 Case Studies

    Directory of Open Access Journals (Sweden)

    Ana Lúcia Pires

    2014-07-01

    Full Text Available Magnetic materials with strong spin-lattice coupling are a powerful set of candidates for multifunctional applications because of their multiferroic, magnetocaloric (MCE, magnetostrictive and magnetoresistive effects. In these materials there is a strong competition between two states (where a state comprises an atomic and an associated magnetic structure that leads to the occurrence of phase transitions under subtle variations of external parameters, such as temperature, magnetic field and hydrostatic pressure. In this review a general method combining detailed magnetic measurements/analysis and first principles calculations with the purpose of estimating the phase transition temperature is presented with the help of two examples (Gd5Si2Ge2 and Tb5Si2Ge2. It is demonstrated that such method is an important tool for a deeper understanding of the (decoupled nature of each phase transition in the materials belonging to the R5(Si,Ge4 family and most possibly can be applied to other systems. The exotic Griffiths-like phase in the framework of the R5(SixGe1-x4 compounds is reviewed and its generalization as a requisite for strong phase competitions systems that present large magneto-responsive properties is proposed.

  4. Visible photoluminescence of porous Si(1-x)Ge(x) obtained by stain etching

    Science.gov (United States)

    Ksendzov, A.; Fathauer, R. W.; George, T.; Pike, W. T.; Vasquez, R. P.; Taylor, A. P.

    1993-01-01

    We have investigated visible photoluminescence (PL) from thin porous Si(1-x)Ge(x) alloy layers prepared by stain etching of molecular-beam-epitaxy-grown material. Seven samples with nominal Ge fraction x varying from 0.04 to 0.41 were studied at room temperature and 80 K. Samples of bulk stain etched Si and Ge were also investigated. The composition of the porous material was determined using X-ray photoemission spectroscopy and Rutherford backscattering techniques to be considerably more Ge-rich than the starting epitaxial layers. While the luminescence intensity drops significantly with the increasing Ge fraction, we observe no significant variation in the PL wavelength at room temperature. This is clearly in contradiction to the popular model based on quantum confinement in crystalline silicon which predicts that the PL energy should follow the bandgap variation of the starting material. However, our data are consistent with small active units containing only a few Si atoms that are responsible for the light emission. Such units are present in many compounds proposed in the literature as the cause of the visible PL in porous Si.

  5. New approach to the growth of low dislocation relaxed SiGe material

    Science.gov (United States)

    Powell, A. R.; Iyer, S. S.; LeGoues, F. K.

    1994-04-01

    In this growth process a new strain relief mechanism operates, whereby the SiGe epitaxial layer relaxes without the generation of threading dislocations within the SiGe layer. This is achieved by depositing SiGe on an ultrathin silicon on insulator (SOI) substrate with a superficial silicon thickness less than the SiGe layer thickness. Initially, the thin Si layer is put under tension due to an equalization of the strain between the Si and SiGe layers. Thereafter, the strain created in the thin Si layer relaxes by plastic deformation. Since the dislocations are formed and glide in the thin Si layer, no threading dislocation is ever introduced in to the upper SiGe material, which appeared dislocation free to the limit of the cross sectional transmission electron microscopy analysis. We thus have a method for producing very low dislocation, relaxes SiGe films with the additional benefit of an SOI substrate.

  6. Hole transport simulations in SiGe cascade quantum wells

    Science.gov (United States)

    Ikonić, Z.; Harrison, P.; Kelsall, R. W.

    2004-03-01

    Hole transport in p-Si/SiGe quantum well cascade structures has been analyzed using a rate equation method with thermal balancing (self-consistent energy balance method). The carrier and energy relaxation due to alloy disorder, acoustic and optical phonon scattering are included. The model includes the in-plane k-space anisotropy. The results are compared to those obtained from Monte Carlo simulations and from the basic particle rate equation method.

  7. Carrier recombination in tailored multilayer Si/Si{sub 1−x}Ge{sub x} nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Mala, S.A. [Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Tsybeskov, L., E-mail: tsybesko@njit.edu [Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Lockwood, D.J.; Wu, X.; Baribeau, J.-M. [National Research Council, Ottawa, ON, Canada KIA 0R6 (Canada)

    2014-11-15

    Photoluminescence (PL) measurements were performed in Si/Si{sub 1−x}Ge{sub x} nanostructures with a single Si{sub 0.92}Ge{sub 0.08} nanometer-thick layer incorporated into Si/Si{sub 0.6}Ge{sub 0.4} cluster multilayers. Under pulsed laser excitation, the PL decay associated with the Si{sub 0.92}Ge{sub 0.08} nano-layer is found to be nearly a 1000 times faster compared to that in Si/Si{sub 0.6}Ge{sub 0.4} cluster multilayers. A model considering Si/SiGe hetero-interface composition and explaining the fast and slow time-dependent recombination rates is proposed.

  8. Monte Carlo simulations of hole dynamics in SiGe/Si terahertz quantum-cascade structures

    Science.gov (United States)

    Ikonić, Z.; Kelsall, R. W.; Harrison, P.

    2004-06-01

    A detailed analysis of hole transport in cascaded p - Si/SiGe quantum well structures is performed using ensemble Monte Carlo simulations. The hole subband structure is calculated using the 6×6 k·p model, and then used to find carrier relaxation rates due to the alloy disorder, acoustic and optical phonon scattering. The simulation accounts for the in-plane k -space anisotropy of both the hole subband structure and the scattering rates. Results are presented for prototype terahertz Si/SiGe quantum cascade structures.

  9. Design and Manufacture of GeSi/Si Superlattice Nanocrystalline Photodetector

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    According to Maxwell's theory, the optical transmission characteristics in GeSi/Si superlattice nanocrystalline layer have been analyzed and calculated. The calculated result shows that when the total thickness L is 340nm, the single mode lightwave can be transmitted only at periodic number M≥15.5. In addition, at the direction of transmission, when the transmission distance is larger than 500μm, the lightwave intensity is decreased greatly. Based on the above parameters, the design and manufacture of GeSi/Si superlattice nanocrystalline photodetector are carried out.

  10. HREM study on stacking structure of SiGe/Si infrared detector

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Stacking structure and defects in SiGe/P-Si infrared detector were studied by using localization high resolutionelectron microscopy (HREM). The photosensitive region in the detector consists of 3 P+-Si0.65 Ge0.35 layers and 2 UD-Si(undoped Si) layers. The interface between Si0.65 Ge0.35 and UD-Si is not sharp and has a transition zone with non-uniform contrast. The misfit stress of interface is distributed gradiently along the normal direction of the interface. Thereforethe crystal defects and serious lattice deformations on the interface have not been found. A defect area with a shape of in-verted triangle exists in the edge of photosensitive region. The main types of the defects in the area are stacking faults andmicrotwins. The stacking faults are on ( 1 11), and the thickness of the most microtwins is less than 4 interplanar spacingand the twin plane is (111). The Si0.65Ge0.35 and UD-Si layers on amorphous SiO2 layer consist of polycrystals grown byrandom nueleation, and are in wave

  11. DC Characteristics of Gamma-ray Irradiated SiGe HBT in Comparison with Si BJT

    Institute of Scientific and Technical Information of China (English)

    MENG Xiang-ti; HUANG Qian; WANG Ji-lin; CHEN Pei-yi; TSIEN Pei-hsin

    2006-01-01

    The changes of DC characteristics of SiGe HBT after being submitted to γ-ray irradiation of 700 krad, 7 000 krad and 10 000 krad were compared to those of Si BJT. Generally speaking, Ib and Ib - Ib0 increase with the doses increasing. For SiGe HBT, with the doses increasing, Ic and Ic - Ic0 as well as the related changes of the current gain (β) will decrease at higher Vbe, while for Si BJT, with the doses increasing, after irradiation, Ib and Ic - Ic0 increase; β and its related changes also decrease with their differences, however, tending to be very small at high doses of 7 000 krad and 10 000 krad. Moreover, given the same doses, the decreases of β are much larger than SiGe HBT, which shows that SiGe HBT's anti-radiation performance proves to be better than Si BJT. Still, in SiGe HBT, some strange phenomena were observed: Ic - Ic0 will increase after the radiation of 7 000 krad in less than 0.65 V and as will β in less than 0.75 V. The mechanism of radiation-induced change in DC characteristics was also discussed.

  12. Strong room temperature electroluminescence from lateral p-SiGe/i-Ge/n-SiGe heterojunction diodes on silicon-on-insulator substrate

    Science.gov (United States)

    Lin, Guangyang; Yi, Xiaohui; Li, Cheng; Chen, Ningli; Zhang, Lu; Chen, Songyan; Huang, Wei; Wang, Jianyuan; Xiong, Xihuan; Sun, Jiaming

    2016-10-01

    A lateral p-Si0.05Ge0.95/i-Ge/n-Si0.05Ge0.95 heterojunction light emitting diode on a silicon-on-insulator (SOI) substrate was proposed, which is profitable to achieve higher luminous extraction compared to vertical junctions. Due to the high carrier injection ratio of heterostructures and optical reflection at the SiO2/Si interface of the SOI, strong room temperature electroluminescence (EL) at around 1600 nm from the direct bandgap of i-Ge with 0.30% tensile strain was observed. The EL peak intensity of the lateral heterojunction is enhanced by ˜4 folds with a larger peak energy than that of the vertical Ge p-i-n homojunction, suggesting that the light emitting efficiency of the lateral heterojunction is effectively improved. The EL peak intensity of the lateral heterojunction, which increases quadratically with injection current density, becomes stronger for diodes with a wider i-Ge region. The CMOS compatible fabrication process of the lateral heterojunctions paves the way for the integration of the light source with the Ge metal-oxide-semiconductor field-effect-transistor.

  13. Comparison of thermoelectric properties of nanostructured Mg2Si, FeSi2, SiGe, and nanocomposites of SiGe–Mg2Si, SiGe–FeSi2

    Directory of Open Access Journals (Sweden)

    Amin Nozariasbmarz

    2016-10-01

    Full Text Available Thermoelectric properties of nanostructured FeSi2, Mg2Si, and SiGe are compared with their nanocomposites of SiGe–Mg2Si and SiGe–FeSi2. It was found that the addition of silicide nanoinclusions to SiGe alloy maintained or increased the power factor while further reduced the thermal conductivity compared to the nanostructured single-phase SiGe alloy. This resulted in ZT enhancement of Si0.88Ge0.12–FeSi2 by ∼30% over the broad temperature range of 500-950 °C compared to the conventional Si0.80Ge0.20 alloy. The Si0.88Ge0.12–Mg2Si nanocomposite showed constantly increasing ZT versus temperature up to 950 °C (highest measured temperature reaching ZT ∼ 1.3. These results confirm the concept of silicide nanoparticle-in-SiGe-alloy proposed earlier by Mingo et al. [Nano Lett. 9, 711–715 (2009].

  14. Energy relaxation in optically excited Si and Ge nanocrystals

    NARCIS (Netherlands)

    S. Saeed

    2014-01-01

    The scientific objective of the research presented in this thesis is to explore energy relaxation processes of optically excited Si and Ge nanocrystals. The identification and deeper understanding of unique energy relaxation paths in these materials will open a new window of opportunity for these ma

  15. Antilocalization of Coulomb Blockade in a Ge-Si Nanowire

    DEFF Research Database (Denmark)

    Higginbotham, Andrew P.; Kuemmeth, Ferdinand; Larsen, Thorvald Wadum

    2014-01-01

    The distribution of Coulomb blockade peak heights as a function of magnetic field is investigated experimentally in a Ge-Si nanowire quantum dot. Strong spin-orbit coupling in this hole-gas system leads to antilocalization of Coulomb blockade peaks, consistent with theory. In particular, the peak...

  16. Electrical and Optical Characterization of Si-Ge-Sn

    Science.gov (United States)

    2012-03-01

    the typical mounting brackets were too large to hold the samples. The FTIR uses a Michelson -type interferometer. The optical path difference is...al., "Tensile-strained, n-type Ge as a Gain Medium for Monolithic Laser Integration on Si," Optical Express 15 (18), 11272 (2007). 32. W. C. Dash

  17. Combined wet and dry cleaning of SiGe(001)

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Wook; Kaufman-Osborn, Tobin; Kim, Hyonwoong [Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093 (United States); Siddiqui, Shariq; Sahu, Bhagawan [TD Research, GLOBALFOUNDRIES USA, Inc., 257 Fuller Road, Albany, New York 12203 (United States); Yoshida, Naomi; Brandt, Adam [Applied Materials, Inc., Santa Clara, California 95054 (United States); Kummel, Andrew C., E-mail: akummel@ucsd.edu [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093 (United States)

    2015-07-15

    Combined wet and dry cleaning via hydrofluoric acid (HF) and atomic hydrogen on Si{sub 0.6}Ge{sub 0.4}(001) surface was studied at the atomic level using ultrahigh vacuum scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and x-ray photoelectron spectroscopy to understand the chemical transformations of the surface. Aqueous HF removes native oxide, but residual carbon and oxygen are still observed on Si{sub 0.6}Ge{sub 0.4}(001) due to hydrocarbon contamination from post HF exposure to ambient. The oxygen contamination can be eliminated by shielding the sample from ambient via covering the sample in the HF cleaning solution until the sample is introduced to the vacuum chamber or by transferring the sample in an inert environment; however, both processes still leave carbon contaminant. Dry in-situ atomic hydrogen cleaning above 330 °C removes the carbon contamination on the surface consistent with a thermally activated atomic hydrogen reaction with surface hydrocarbon. A postdeposition anneal at 550 °C induces formation of an atomically flat and ordered SiGe surface observed by STM. STS verifies that the wet and dry cleaned surface has an unpinned Fermi level with no states between the conduction and valence band edge comparable to sputter cleaned SiGe surfaces.

  18. SiGe Building Blocks for Microwave Frequency Synthesizers

    OpenAIRE

    Vaucher, Cicero S.; Apostolidou, M; Farrugia, Andrew; Praamsma, Louis

    2004-01-01

    Implementations of Ku- and Ka-band PLL building blocks in the Philips QUBiC4G SiGe technology are presented: a 10 GHz fully-integrated low-phase-noise differential Colpttis oscillator, a 25 GHz low-power adaptive prescaler, and a 18 GHz truly-modular fully-programmable frequency divider.

  19. Reactivity of [Ge9 {Si(SiMe3 )3 }3 ](-) Towards Transition-Metal M(2+) Cations: Coordination and Redox Chemistry.

    Science.gov (United States)

    Kysliak, Oleksandr; Schrenk, Claudio; Schnepf, Andreas

    2016-12-23

    Recently the metalloid cluster compound [Ge9 Hyp3 ](-) (1; Hyp=Si(SiMe3 )3 ) was oxidatively coupled by an iron(II) salt to give the largest metalloid Group 14 cluster [Ge18 Hyp6 ]. Such redox chemistry is also possible with different transition metal (TM) salts TM(2+) (TM=Fe, Co, Ni) to give the TM(+) complexes [Fe(dppe)2 ][Ge9 Hyp3 ] (3; dppe=1,2-bis(diphenylphosphino)ethane), [Co(dppe)2 ][Ge9 Hyp3 ] (4), [Ni(dppe)(Ge9 Hyp3 )] (5) and [Ni(dppe)2 (Ge9 Hyp3 )](+) (6). Such a redox reaction does not proceed for Mn, for which a salt metathesis gives the first open shell [Hyp3 Ge9 -M-Ge9 Hyp3 ] cluster (2; M=Mn). The bonding of the transition metal atom to 1 is also possible for Ni (e.g., compound 6), in which one or even two nickel atoms can bind to 1. In contrast to this in case of the Fe and Co compounds 3 and 4, respectively, the transition-metal atom is not bound to the Ge9 core of 1. The synthesis and the experimentally determined structures of 2-6 are presented. Additionally the bonding within 2-6 is analyzed and discussed with the aid of EPR measurements and quantum chemical calculations. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Thermoelectric properties of Mg2X (X = Si, Ge) based bulk and quantum well systems

    Science.gov (United States)

    Yelgel, Övgü Ceyda

    2017-01-01

    Mg2X (X = Si, Ge) compounds are promising thermoelectric materials for middle temperature applications due to good thermoelectric properties, nontoxicity, and abundantly available constituent elements. So far, these materials used in applications have all been in bulk form. Herein we report a full theory of thermoelectric transport properties of 3D bulk and 2D quantum well systems. The main aim of this present work is to show the effect of quantum confinement on the enhancement of the thermoelectric figure of merit theoretically. Results are given for n-type Mg2 Si0.5 Ge0.5 solid solutions and n-type Mg2Si/Mg2Ge/Mg2Si quantum well systems where the values of well widths are taken as 10 nm, 15 nm, and 20 nm, respectively. The n-type doping is made by using Sb- and La-elements as dopants. Experimental results for solid solutions are included to provide demonstration of proof of principle for the theoretical model applied for 3D bulk structures. The maximum thermoelectric figure of merits of Lax Mg2 -x Si0.49 Ge0.5 Sb0.01 solid solutions are obtained to be 0.64 and 0.56 at 800 K for x = 0 and x = 0.01 sample, respectively. While, at the same temperature, due to the relatively low phonon thermal conductivity the state-of-the-art ZT values of 2.41 and 2.26 have been attained in the Mg2Si/Mg2Ge/Mg2Si quantum well samples with 0.01 wt. % Sb-doped and 0.01 wt. % Sb- and 0.01 wt. % La-doped, respectively.

  1. The microstructure of Ge/Si layers grown at low temperature

    Science.gov (United States)

    Roddatis, V. V.; Vasiliev, A. L.; Kovalchuk, M. V.

    2013-11-01

    Multilayer Si/Ge heterostructures with the thickness of Ge layers varying from 2 to 12 monolayers (ML) were formed by molecular beam epitaxy (MBE) on the (001) Si substrates at 300°C (Ge) and 450°C (Si). The study of the Si/Ge heterostructures was performed by transmission and Cs corrected scanning transmission electron microscopy (STEM). It was shown that the growth of Ge layers up to thickness of 5 ML occurs through the Frank - van der Merwe mechanism. For thicker Ge layers the growth mechanism of the Si-Ge heterostructure changes to Stranski - Krastanov with Si-Ge islands having the shape of inverted pyramids. The Si-Ge layer intermixing was discussed.

  2. Local Structure of Ge/Si(100) Self-Assembled Quantum Dot

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Local structure of uncapped and Si-capped Ge quantum dots grownon Si(100) has been probed by X-ray absorption fine structure spectroscopy. It is found that the uncapped Ge dots are partially oxidized and partially alloyed with Si. The amount of Ge present in the Ge phase is found to be about 20-30%. In the Si-capped sample, Ge is found to be dissolved in silicon, the fraction of Ge atoms existing as pure Ge phase being not more than 10%.

  3. Toward 17µm pitch heterogeneously integrated Si/SiGe quantum well bolometer focal plane arrays

    Science.gov (United States)

    Ericsson, Per; Fischer, Andreas C.; Forsberg, Fredrik; Roxhed, Niclas; Samel, Björn; Savage, Susan; Stemme, Göran; Wissmar, Stanley; Öberg, Olof; Niklaus, Frank

    2011-06-01

    Most of today's commercial solutions for un-cooled IR imaging sensors are based on resistive bolometers using either Vanadium oxide (VOx) or amorphous Silicon (a-Si) as the thermistor material. Despite the long history for both concepts, market penetration outside high-end applications is still limited. By allowing actors in adjacent fields, such as those from the MEMS industry, to enter the market, this situation could change. This requires, however, that technologies fitting their tools and processes are developed. Heterogeneous integration of Si/SiGe quantum well bolometers on standard CMOS read out circuits is one approach that could easily be adopted by the MEMS industry. Due to its mono crystalline nature, the Si/SiGe thermistor material has excellent noise properties that result in a state-ofthe- art signal-to-noise ratio. The material is also stable at temperatures well above 450°C which offers great flexibility for both sensor integration and novel vacuum packaging concepts. We have previously reported on heterogeneous integration of Si/SiGe quantum well bolometers with pitches of 40μm x 40μm and 25μm x 25μm. The technology scales well to smaller pixel pitches and in this paper, we will report on our work on developing heterogeneous integration for Si/SiGe QW bolometers with a pixel pitch of 17μm x 17μm.

  4. Material gain engineering in GeSn/Ge quantum wells integrated with an Si platform

    Science.gov (United States)

    Mączko, H. S.; Kudrawiec, R.; Gladysiewicz, M.

    2016-09-01

    It is shown that compressively strained Ge1‑xSnx/Ge quantum wells (QWs) grown on a Ge substrate with 0.1 ≤ x ≤ 0.2 and width of 8 nm ≤ d ≤ 14 nm are a very promising gain medium for lasers integrated with an Si platform. Such QWs are type-I QWs with a direct bandgap and positive transverse electric mode of material gain, i.e. the modal gain. The electronic band structure near the center of Brillouin zone has been calculated for various Ge1‑xSnx/Ge QWs with use of the 8-band kp Hamiltonian. To calculate the material gain for these QWs, occupation of the L valley in Ge barriers has been taken into account. It is clearly shown that this occupation has a lot of influence on the material gain in the QWs with low Sn concentrations (Sn  15%). However, for QWs with Sn > 20% the critical thickness of a GeSn layer deposited on a Ge substrate starts to play an important role. Reduction in the QW width shifts up the ground electron subband in the QW and increases occupation of the L valley in the barriers instead of the Γ valley in the QW region.

  5. Growth and self-organization of SiGe nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Aqua, J.-N., E-mail: aqua@insp.jussieu.fr [Institut des Nanosciences de Paris, Université Pierre et Marie Curie Paris 6 and CNRS UMR 7588, 4 place Jussieu, 75252 Paris (France); Berbezier, I., E-mail: isabelle.berbezier@im2np.fr [Institut Matériaux Microélectronique Nanoscience de Provence, Aix-Marseille Université, UMR CNRS 6242, 13997 Marseille (France); Favre, L. [Institut Matériaux Microélectronique Nanoscience de Provence, Aix-Marseille Université, UMR CNRS 6242, 13997 Marseille (France); Frisch, T. [Institut Non Linéaire de Nice, Université de Nice Sophia Antipolis, UMR CNRS 6618, 1361 routes des Lucioles, 06560 Valbonne (France); Ronda, A. [Institut Matériaux Microélectronique Nanoscience de Provence, Aix-Marseille Université, UMR CNRS 6242, 13997 Marseille (France)

    2013-01-01

    Many recent advances in microelectronics would not have been possible without the development of strain induced nanodevices and bandgap engineering, in particular concerning the common SiGe system. In this context, a huge amount of literature has been devoted to the growth and self-organization of strained nanostructures. However, even if an overall picture has been drawn out, the confrontation between theories and experiments is still, under various aspects, not fully satisfactory. The objective of this review is to present a state-of-the-art of theoretical concepts and experimental results on the spontaneous formation and self-organization of SiGe quantum dots on silicon substrates. The goal is to give a comprehensive overview of the main experimental results on the growth and long time evolution of these dots together with their morphological, structural and compositional properties. We also aim at describing the basis of the commonly used thermodynamic and kinetic models and their recent refinements. The review covers the thermodynamic theory for different levels of elastic strain, but focuses also on the growth dynamics of SiGe quantum dots in several experimental circumstances. The strain driven kinetically promoted instability, which is the main form of instability encountered in the epitaxy of SiGe nanostructures at low strain, is described. Recent developments on its continuum description based on a non-linear analysis particularly useful for studying self-organization and coarsening are described together with other theoretical frameworks. The kinetic evolution of the elastic relaxation, island morphology and film composition are also extensively addressed. Theoretical issues concerning the formation of ordered island arrays on a pre-patterned substrate, which is governed both by equilibrium ordering and kinetically-controlled ordering, are also reported in connection with the experimental results for the fabrication technology of ordered arrays of SiGe

  6. Intersubband carrier scattering in n - and p-Si/SiGe quantum wells with diffuse interfaces

    Science.gov (United States)

    Valavanis, A.; Ikonić, Z.; Kelsall, R. W.

    2008-02-01

    Scattering rate calculations in two-dimensional Si/Si1-xGex systems have typically been restricted to rectangular Ge profiles at interfaces between layers. Real interfaces, however, may exhibit diffuse Ge profiles either by design or as a limitation of the growth process. It is shown here that alloy disorder scattering dramatically increases with Ge interdiffusion in (100) and (111) n -type quantum wells, but remains almost constant in (100) p -type heterostructures. It is also shown that smoothing of the confining potential leads to large changes in subband energies and scattering rates, and a method is presented for calculating growth process tolerances.

  7. Research progress of self-organized Ge quantum dots on Si substrate

    Institute of Scientific and Technical Information of China (English)

    HUANG Changjun; YU Jinzhong; WANG Qiming

    2004-01-01

    A review is presented on recent research development of self-organized Ge/Si quantum dots (QDs).Emphasis is put on the morphological evolution of the Ge quantum dots grown on Si (001) substrate,the structure analysis of multilayer Ge QDs,the optical and electronic properties of these nanostructures,and the approaches to fabricating ordered Ge quantum dots.

  8. Mn-doped Ge and Si: A Review of the Experimental Status

    Directory of Open Access Journals (Sweden)

    Heidemarie Schmidt

    2010-11-01

    Full Text Available Diluted ferromagnetic semiconductors (FMS are in the focus of intense research due to their potential applications in spintronics and their striking new physical properties. So far Mn-doped III-V compound semiconductors such as GaMnAs are the most important and best understood ones, but they are ferromagnetic only at well below room temperature. An interesting alternative could be magnetic semiconductors based on elemental semiconductors, also owing to their compatibility with Si microelectronics. In the last decades, considerable amount of work has been devoted to fabricate Mn-doped Ge and Si FMS. In this article, the structural, magnetic and magneto-transport properties of Mn-doped Ge and Si will be reviewed.

  9. Mn-doped Ge and Si: A Review of the Experimental Status

    Science.gov (United States)

    Zhou, Shengqiang; Schmidt, Heidemarie

    2010-01-01

    Diluted ferromagnetic semiconductors (FMS) are in the focus of intense research due to their potential applications in spintronics and their striking new physical properties. So far Mn-doped III-V compound semiconductors such as GaMnAs are the most important and best understood ones, but they are ferromagnetic only at well below room temperature. An interesting alternative could be magnetic semiconductors based on elemental semiconductors, also owing to their compatibility with Si microelectronics. In the last decades, considerable amount of work has been devoted to fabricate Mn-doped Ge and Si FMS. In this article, the structural, magnetic and magneto-transport properties of Mn-doped Ge and Si will be reviewed. PMID:28883369

  10. Electron transport in n-doped Si/SiGe quantum cascade structures

    NARCIS (Netherlands)

    Lazic, I.; Ikonic, Z.; Milanovic, V.; Kelsall, R.W.; Indjin, D.; Harrison, P.

    2007-01-01

    An electron transport model in n-Si/SiGe quantum cascade or superlattice structures is described. The model uses the electronic structure calculated within the effective-mass complex-energy framework, separately for perpendicular (Xz) and in-plane (Xxy) valleys, the degeneracy of which is lifted by

  11. Electron transport in n-doped Si/SiGe quantum cascade structures

    NARCIS (Netherlands)

    Lazic, I.; Ikonic, Z.; Milanovic, V.; Kelsall, R.W.; Indjin, D.; Harrison, P.

    2007-01-01

    An electron transport model in n-Si/SiGe quantum cascade or superlattice structures is described. The model uses the electronic structure calculated within the effective-mass complex-energy framework, separately for perpendicular (Xz) and in-plane (Xxy) valleys, the degeneracy of which is lifted by

  12. High-Performance Deep SubMicron CMOS Technologies with Polycrystalline-SiGe Gates

    NARCIS (Netherlands)

    Ponomarev, Youri V.; Stolk, Peter A.; Salm, Cora; Schmitz, Jurriaan; Woerlee, P.H.

    2000-01-01

    The use of polycrystalline SiGe as the gate material for deep submicron CMOS has been investigated. A complete compatibility to standard CMOS processing is demonstrated when polycrystalline Si is substituted with SiGe (for Ge fractions below 0.5) to form the gate electrode of the transistors. Perfor

  13. High-Performance Deep SubMicron CMOS Technologies with Polycrystalline-SiGe Gates

    NARCIS (Netherlands)

    Ponomarev, Youri V.; Stolk, Peter A.; Salm, Cora; Schmitz, Jurriaan; Woerlee, P.H.

    2000-01-01

    The use of polycrystalline SiGe as the gate material for deep submicron CMOS has been investigated. A complete compatibility to standard CMOS processing is demonstrated when polycrystalline Si is substituted with SiGe (for Ge fractions below 0.5) to form the gate electrode of the transistors.

  14. Misfit dislocation gettering by substrate pit-patterning in SiGe films on Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Grydlik, Martyna; Groiss, Heiko; Brehm, Moritz; Schaeffler, Friedrich [Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz (Austria); Boioli, Francesca; Montalenti, Francesco; Miglio, Leo [L-NESS and Department of Material Science, University of Milano-Bicocca (Italy); Gatti, Riccardo; Devincre, Benoit [LEM, CNRS/ONERA, Chatillon Cedex (France)

    2012-07-02

    We show that suitable pit-patterning of a Si(001) substrate can strongly influence the nucleation and the propagation of dislocations during epitaxial deposition of Si-rich Si{sub 1-x}Ge{sub x} alloys, preferentially gettering misfit segments along pit rows. In particular, for a 250 nm layer deposited by molecular beam epitaxy at x{sub Ge} = 15%, extended film regions appear free of dislocations, by atomic force microscopy, as confirmed by transmission electron microscopy sampling. This result is quite general, as explained by dislocation dynamics simulations, which reveal the key role of the inhomogeneous distribution in stress produced by the pit-patterning.

  15. Extended point defects in crystalline materials: Ge and Si.

    Science.gov (United States)

    Cowern, N E B; Simdyankin, S; Ahn, C; Bennett, N S; Goss, J P; Hartmann, J-M; Pakfar, A; Hamm, S; Valentin, J; Napolitani, E; De Salvador, D; Bruno, E; Mirabella, S

    2013-04-12

    B diffusion measurements are used to probe the basic nature of self-interstitial point defects in Ge. We find two distinct self-interstitial forms--a simple one with low entropy and a complex one with entropy ∼30  k at the migration saddle point. The latter dominates diffusion at high temperature. We propose that its structure is similar to that of an amorphous pocket--we name it a morph. Computational modeling suggests that morphs exist in both self-interstitial and vacancylike forms, and are crucial for diffusion and defect dynamics in Ge, Si, and probably many other crystalline solids.

  16. IBA study of SiGe/SiO{sub 2} nanostructured multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Barradas, Nuno P., E-mail: nunoni@ctn.ist.utl.pt [Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10 (ao km 139,7), 2695-066 Bobadela LRS (Portugal); Laboratório de Engenharia Nuclear, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10 (ao km 139,7), 2695-066 Bobadela LRS (Portugal); Alves, E. [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Vieira, E.M.F. [Centre of Physics and Physics Department, University of Minho, 4710-057 Braga (Portugal); Parisini, A. [CNR-IMM Sezione di Bologna, via P. Gobetti 101, 40129 Bologna (Italy); Conde, O. [Physics Department and ICEMS, University of Lisbon, 1749-016 Lisboa (Portugal); Martín-Sánchez, J. [Laser Processing Group, Instituto de Óptica, CSIC, C/Serrano 121, 28006 Madrid (Spain); Rolo, A.G. [Centre of Physics and Physics Department, University of Minho, 4710-057 Braga (Portugal); Chahboun, A. [Centre of Physics and Physics Department, University of Minho, 4710-057 Braga (Portugal); FST Tanger, Physics Department, BP 416 Tanger (Morocco); Gomes, M.J.M. [Centre of Physics and Physics Department, University of Minho, 4710-057 Braga (Portugal)

    2014-07-15

    SiGe/SiO{sub 2} multilayers with layer thickness of 5 nm were deposited with RF magnetron sputtering. The as deposited samples had well defined SiGe amorphous layers. Different annealing treatments were made to promote the formation of SiGe nanocrystals. We report an ion beam analysis study with the Rutherford backscattering and elastic recoil analysis detection techniques, in order to determine the thickness and composition of the nanolayers, and gain insight into the evolution of the roughness of the layers. The results are correlated with other structural properties of the samples, as measured with complementary techniques such as grazing incidence X-ray diffraction annular dark field scanning transmission electron microscopy and high resolution transmission electron microscopy.

  17. Materials and devices for quantum information processing in Si/SiGe

    Energy Technology Data Exchange (ETDEWEB)

    Sailer, Juergen

    2010-12-15

    In this thesis, we cover and discuss the complete way from material science, the fabrication of two-dimensional electron systems (2DES) in Si/SiGe heterostructures in molecular beam epitaxy (MBE), to quantum effects in few-electron devices based on these samples. We applied and compared two different approaches for the creation of pseudo-substrates that are as smooth, relaxed and defect free as possible. In the 'graded buffer' concept, starting from pure Si, the Ge content of the SiGe alloy is slowly and linearly increased until the desired Ge content is reached. In contrast, in the so-called 'low-temperature Si' concept, the SiGe alloy is deposited directly with the final Ge content, but onto a layer of highly defective Si. In terms of crystal defects, the 'graded buffer' turned out to be superior in comparison to the 'low-temperature Si' concept at the expense of a significantly higher material consumption. By continued optimization of the growth process, aiming at reducing the influence of the impurity, it nevertheless became possible to improve the charge carrier mobility from a mere 2000 cm{sup 2}/(Vs) to a record mobility exceeding 100 000 cm{sup 2}/(Vs). Within this work, we extended our MBE system with an electron beam evaporator for nuclear spin free {sup 28}Si. Together with the already existing effusion cell for {sup 70}Ge we were able to realize first 2DES in a nuclear spin free environment after successfully putting it to operation. The highest mobility 2DES in a nuclear spin free environment which have been realized in this thesis exhibited electron mobilities of up to 55 000 cm{sup 2}/(Vs). Quantum effects in Si/SiGe have been investigated in two- and zero-dimensional nanostructures. A remarkable phenomenon in the regime of the integer quantum Hall effect in Si/SiGe 2DES has been discovered and researched. For applications in quantum information processing and for the creation of qubits it is mandatory to

  18. Regrowth characteristics of SiGe/Si by IBIEC and SPEG

    Energy Technology Data Exchange (ETDEWEB)

    Awane, K.; Kokubo, Y.; Yomogida, M. [Graduate School of Engineering, Hosei University, Koganei, Tokyo 184-8584 (Japan); Nishimura, T. [Reseach Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Yamamoto, Y., E-mail: hiro@edl.ei.hosei.ac.jp [Graduate School of Engineering, Hosei University, Koganei, Tokyo 184-8584 (Japan)

    2013-07-15

    Single crystalline Si{sub 1−x}Ge{sub x}/Si with three kinds of Ge contents (x: 0.05, 0.1, and 0.2) with thicknesses of 400–440 nm were amorphized by 500 keV (x: 0.05 and 0.1) and 600 keV (x: 0.2) Ge ion beam bombardment to a fluence of 1.0 × 10{sup 16} ions/cm{sup 2} at room temperature. The regrowth behavior of the damaged layers were compared between ion beam induced epitaxial crystallization (IBIEC) by 2.0 MeV Ge ions at 300 °C to fluences of 1.0–3.0 × 10{sup 16} ions/cm{sup 2} and solid phase epitaxial growth (SPEG) carried out in a flowing N{sub 2} ambient for up to 40 min at 600 °C. Rutherford backscattering spectroscopy (RBS) with channeling techniques revealed that crystallinity improvement by IBIEC tended to be saturated with increasing fluence while crystallinity improvement by SPEG was proceeded with increasing annealing time and relatively high quality SiGe layers were obtained. Crystallinity improvement was more rapid and pronounced for SiGe with higher Ge concentration both in IBIEC and SPEG. In contrast to the case of SPEG at 600 °C, transmission electron microscope (TEM) image in SiGe treated by IBIEC showed that bunches of dislocation loops remained as islands surrounded by single crystalline lattice layers image, leading to the high RBS aligned yield even after completion of the layer-by-layer regrowth.

  19. Magnetic structure of Gd{sub 5}Si{sub 2}Ge{sub 2} and Gd{sub 5}Si{sub 2}Ge{sub 1.9}M{sub 0.1} (M = Ga, Cu)

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, E; Rodriguez-Velamazan, J A; Wang, G F; Burriel, R [Instituto de Ciencia de Materiales de Aragon, Departamento de Fisica de la Materia Condensada, CSIC-University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Cuello, G; RodrIguez-Carvajal, J, E-mail: elias@unizar.e [Institute Laue-Langevin, 6 rue Jules Horowitz, 38000 Grenoble (France)

    2010-10-10

    Powder x-ray diffraction patterns of the doped compounds Gd{sub 5}Si{sub 2}Ge{sub 1.9}M{sub 0.1} (M = Ga, Cu) show the same crystal structure, orthorhombic Gd{sub 5}Si{sub 4}-type, in the ferromagnetic and paramagnetic phases. This is different from Gd{sub 5}Si{sub 2}Ge{sub 2}, whose paramagnetic phase is monoclinic. The magnetic structure at low temperature, solved from diffraction experiments with hot neutrons, is the same in all the three compounds, collinear ferromagnetic with moments along the crystal b-axis, or F{sub y}F{sub By} according to Bertaut's notation. These results, combined with those of heat capacity and magnetocaloric effect, indicate, similarly to Gd{sub 5}Si{sub 4}, a second-order, purely magnetic, transition in the doped compounds explaining the absence of hysteresis.

  20. Effect of Si interface surface roughness to the tunneling current of the Si/Si{sub 1-x}Ge{sub x}/Si heterojunction bipolar transistor

    Energy Technology Data Exchange (ETDEWEB)

    Hasanah, Lilik, E-mail: lilikhasanah@upi.edu; Suhendi, Endi; Tayubi, Yuyu Rahmat; Yuwono, Heru [Department of Physics Education, Universitas Pendidikan Indonesia, Jl. Setiabudhi 229 Bandung 40154 (Indonesia); Nandiyanto, Asep Bayu Dani [Department Kimia, Universitas Pendidikan Indonesia, Jl. Setiabudhi 229 Bandung 40154 (Indonesia); Murakami, Hideki [Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8527 (Japan); Khairrurijal [Physics of Electronic Materials Research Division, Institut Teknologi Bandung, Bandung 40132 (Indonesia)

    2016-02-08

    In this work we discuss the surface roughness of Si interface impact to the tunneling current of the Si/Si{sub 1-x}Ge{sub x}/Si heterojunction bipolar transistor. The Si interface surface roughness can be analyzed from electrical characteristics through the transversal electron velocity obtained as fitting parameter factor. The results showed that surface roughness increase as Ge content of virtual substrate increase This model can be used to investigate the effect of Ge content of the virtual substrate to the interface surface condition through current-voltage characteristic.

  1. Magnetic Properties of Cr-based Ternary Compound CrAlGe

    Science.gov (United States)

    Yoshinaga, Soshi; Mitsui, Yoshifuru; Umetsu, Rie Y.; Koyama, Keiichi

    Structural and magnetic properties of Cr-based compound CrAlGe were investigated. The crystal structure was found to be an orthorhombic TiSi2-type with lattice parameters a = 0.4770 nm, b = 0.8254 nm and c = 0.8725 nm at room temperature. Magnetization curve of CrAlGe showed the ferromagnetic behavior. The saturation magnetic moment, spontaneous magnetic moment and Curie temperature of CrAlGe were determined to be 0.45 μB/f.u., 0.41 μB/f.u. and TC = 80 K, respectively. For the temperature T below 30 K, the decrease in the square of the spontaneous magnetization M0(T)2 was proportional to T2. However, for 30 Ge is a weak itinerant electron ferromagnet.

  2. Growth and Characterization of Bulk GeSi Solid Solutions

    Science.gov (United States)

    Ritter, Timothy M.

    1999-01-01

    In this work we have grown and characterized several GeSi samples in order to investigate the effects that Silicon concentration, applied magnetic field, and liquid encapsulation have on crystalline quality. Characterization techniques include NDIC microscopy and microprobe spectroscopy. Two samples were grown with a Silicon concentration of approximately 3% and are compared to previous growths having a Silicon fraction of approximately 5%. Growth conditions for one of these samples was varied with the presence of an external applied magnetic field to investigate the possibility of magnetic field damping. A comparison between these two ingots, and with previously grown material, revealed no clear improvement in sample crystalline quality. Three additional samples were grown using a CaCl2 liquid encapsulation technique that produced GeSi material with improved structural quality over previous samples. Comparisons to prior non-encapsulation grown material, details of our methodology, and suggestions for further improvements are discussed.

  3. Design of Ge/SiGe quantum-confined Stark effect modulators for CMOS compatible photonics

    Science.gov (United States)

    Lever, Leon; Ikonić, Zoran; Valavanis, Alex; Kelsall, Robert W.

    2010-02-01

    A simulation technique for modeling optical absorption in Ge/SiGe multiple quantum well (MQW) heterostructures is described, based on a combined 6 × 6 k • p hole wave-function a one-band effective mass electron wavefunction calculation. Using this model, we employ strain engineering to target a specific applications-oriented wavelength, namely 1310 nm, and arrive at a design for a MQW structure to modulate light at this wavelength. The modal confinement in a proposed device is then found using finite-element modeling, and we estimate the performance of a proposed waveguide-integrated electroabsorption modulator.

  4. Room-temperature direct-bandgap photoluminescence from strain-compensated Ge/SiGe multiplequantum wells on silicon

    Institute of Scientific and Technical Information of China (English)

    Hu Wei-Xuan; Cheng Bu-Wen; Xue Chun-Lai; Zhang Guang-Ze; Su Shao-Jian; Zuo Yu-Hua; Wang Qi-Ming

    2012-01-01

    Strain-compensated Ge/Si0.15Ge0.s5 multiple quantum wells were grown on an Si0.1Ge0.9 virtual substrate using ultrahigh vacuum chemical vapor deposition technology on an n+-Si(001) substrate.Photoluminescence measurements were performed at room temperature,and the quantum confinement effect of the direct-bandgap transitions of a Ge quantum well was observed,which is in good agreement with the calculated results.The luminescence mechanism was discussed by recombination rate analysis and the temperature dependence of the luminescence spectrum.

  5. Thermoelectric Properties of Czochralski GeSi Crystal

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In order to discuss the application possibility of SiGe crystal in thermoelectric materials, we investigated the thermoelectric properties of several silicon-germanium alloys with different content, orientation and electric conductive type. As discussed in the experiment result, the absolute value of Seebeck coefficient fluctuates from 300 to 600 μV/K in the whole temperature range. In the present paper, the relationship of Seebeck coefficient against content, orientation and electric conductive type is summarized in detail. The Seebeck coefficient of the sample with 〈111〉orientation is smaller than that in 〈100〉 at the same temperature. Absolute value of P-type is larger than that of N-type except pure Ge. But as the temperature increases, the absolute value of pure Ge decreases many times as quickly as that of other specimens. In addition, the specimens of bulk GeSi alloy crystals for experiment were grown by the Czochralski method through varying the pulling rate during the growing process.

  6. Ultralow Resistivity Ge:Sb heterostructures on Si Using Hydride Epitaxy of Deuterated Stibine and Trigermane.

    Science.gov (United States)

    Xu, Chi; Senaratne, Charutha L; Sims, Patrick; Kouvetakis, John; Menéndez, José

    2016-09-14

    The nonconventional deuterated stibine (SbD3) compound has been used for the first time in combination with trigermane (Ge3H8) to produce hyper-doped Ge-on-Si films with carrier concentrations n > 10(20) cm(-3) and record-low resistivities ρ = 1.8 × 10(-4) Ω cm. The growth takes place on Ge and Ge1-xSix buffered Si(100) wafers at ultralow temperatures (∼330 °C) at which Sb diffusion is negligible, leading to extremely flat atomic profiles of the constituents. The Sb substitution in the Ge lattice is determined by RBS channeling and corroborated by high-resolution XRD, which also reveal a systematic increase in lattice constant vs concentration, as expected due to the incorporation of the larger Sb. High-resolution TEM illustrates defect-free monocrystalline structures with device-quality morphologies. The electrical characteristics of the samples are measured using Hall effect and resistivity measurements combined with contactless infrared ellipsometry and are found to be consistent with an extrapolation of the bulk Ge:Sb properties to the high carrier concentrations achieved in our films. The Sb/Ge ratio in the doped layers is approximately the same as that in the precursor reaction mixture, indicating a highly efficient Sb incorporation afforded by the compatible reactivity of the molecules employed in this study. The resultant films are attractive for next generation germanium technologies that require low-resistance n+ junctions or a Fermi level that approaches the direct gap minimum in the conduction band, which drastically enhances the optical emission efficiency of n-type Ge.

  7. Electrical characterization Of SiGe thin films

    OpenAIRE

    1991-01-01

    An apparatus for measuring electrical resistivity and Hall coefficient on both thin films and bulk material over a temperature range of 300K to 1300K has been built. A unique alumina fixture, with four molybdenum probes, allows arbitrarily shaped samples, up to 2.5 cm diameter, to be measured using van der Pauw's method. The system is fully automated and is constructed with commercially available components. Measurements of the electrical properties of doped and undoped Si-Ge thin films, gro...

  8. Numerical simulation of microstructure of the GeSi alloy

    Energy Technology Data Exchange (ETDEWEB)

    Rasin, I.

    2006-09-08

    The goal of this work is to investigate pattern formation processes on the solid-liquid interface during the crystal growth of GeSi. GeSi crystals with cellular structure have great potential for applications in -ray and neutron optics. The interface patterns induce small quasi-periodic distortions of the microstructure called mosaicity. Existence and properties of this mosaicity are important for the application of the crystals. The properties depend on many factors; this dependence, is currently not known even not qualitatively. A better understanding of the physics near the crystal surface is therefore required, in order to optimise the growth process. There are three main physical processes in this system: phase-transition, diffusion and melt flow. Every process is described by its own set of equations. Finite difference methods and lattice kinetic methods are taken for solving these governing equations. We have developed a modification of the kinetic methods for the advectiondiffusion and extended this method for simulations of non-linear reaction diffusion equations. The phase-field method was chosen as a tool for describing the phase-transition. There are numerous works applied for different metallic alloys. An attempt to apply the method directly to simulation GeSi crystal growth showed that this method is unstable. This instability has not been observed in previous works due to the much smaller scale of simulations. We introduced a modified phase-field scheme, which enables to simulate pattern formation with the scale observed in experiment. A flow in the melt was taken in to account in the numerical model. The developed numerical model allows us to investigate pattern formation in GeSi crystals. Modelling shows that the flow near the crystal surface has impact on the patterns. The obtained patterns reproduce qualitatively and in some cases quantitatively the experimental results. (orig.)

  9. Development of Microwave SiGe Heterojunction Bipolar Transistors

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The microwave SiGe Heterojunction Bipolar Transistors (HBT) were fabricated by the material grown with home-made high vacuum/rapid thermal processing chemical vapor deposition equipment. The HBTs show good performance and industrial use value. The current gain is beyond 100;the breakdown voltage BVceo is 3.3V,and the cut-off frequency is 12.5GHz which is measured in packaged form.

  10. Magnetic structures of RCu{sub x}Ge{sub 2} (R=Ho, Er) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Gil, A.; Kaczorowski, D.; Hernandez-Velasco, J.; Penc, B.; Wawrzynska, E.; Szytula, A

    2004-12-14

    Neutron powder diffraction and magnetic measurements have been carried out on RCu{sub x}Ge{sub 2} (R=Ho, Er) compounds. Both compounds crystallize in the orthorhombic CeNiSi{sub 2}-type structure (space group Cmcm) and they are antiferromagnets with the Neel temperature equal to 4.5 K for R=Er and 8.0 K for R=Ho. Neutron diffraction measurements indicate the presence of collinear magnetic structures of the G{sub z} mode in HoCu{sub 0.33}Ge{sub 2} and G{sub x} mode in ErCu{sub 0.25}Ge{sub 2}.

  11. Carrier Mobility Enhancement of Tensile Strained Si and SiGe Nanowires via Surface Defect Engineering.

    Science.gov (United States)

    Ma, J W; Lee, W J; Bae, J M; Jeong, K S; Oh, S H; Kim, J H; Kim, S-H; Seo, J-H; Ahn, J-P; Kim, H; Cho, M-H

    2015-11-11

    Changes in the carrier mobility of tensile strained Si and SiGe nanowires (NWs) were examined using an electrical push-to-pull device (E-PTP, Hysitron). The changes were found to be closely related to the chemical structure at the surface, likely defect states. As tensile strain is increased, the resistivity of SiGe NWs deceases in a linear manner. However, the corresponding values for Si NWs increased with increasing tensile strain, which is closely related to broken bonds induced by defects at the NW surface. Broken bonds at the surface, which communicate with the defect state of Si are critically altered when Ge is incorporated in Si NW. In addition, the number of defects could be significantly decreased in Si NWs by incorporating a surface passivated Al2O3 layer, which removes broken bonds, resulting in a proportional decrease in the resistivity of Si NWs with increasing strain. Moreover, the presence of a passivation layer dramatically increases the extent of fracture strain in NWs, and a significant enhancement in mobility of about 2.6 times was observed for a tensile strain of 5.7%.

  12. Nondiffusive lattice thermal transport in Si-Ge alloy nanowires

    Science.gov (United States)

    Upadhyaya, M.; Aksamija, Z.

    2016-11-01

    We present a calculation of the lattice thermal conductivity of Si-Ge nanowires (NWs), based on solving the Boltzmann transport equation by the Monte Carlo method of sampling the phonon mean free paths. We augment the previous work with the full phonon dispersion and a partially diffuse momentum-dependent specularity model for boundary roughness scattering. We find that phonon flights are comprised of a mix of long free flights over several μ m interrupted by bursts of short flights, resulting in a heavy-tailed distribution of flight lengths, typically encountered in Lévy walk dynamics. Consequently, phonon transport in Si-Ge NWs is neither entirely ballistic nor diffusive; instead, it falls into an intermediate regime called superdiffusion where thermal conductivity scales with the length of the NW as κ ∝Lα with the exponent of length dependence α ≈0.33 over a broad range of wire lengths 10 nm thermal conductivity in Si-Ge alloy NWs is length dependent up to 10 μ m and therefore can be tuned for thermoelectric applications.

  13. Electronic properties of Fibonacci and random Si-Ge chains

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcelos, M S [Escola de Ciencias e Tecnologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN (Brazil); Azevedo, David L; Hadad, A [Departamento de Fisica, Universidade Federal do Maranhao 65080-040, Sao LuIs-MA (Brazil); Galvao, D S, E-mail: mvasconcelos@ect.ufrn.br [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas CP 6165, 13083-970 Campinas, SP (Brazil)

    2011-10-12

    In this paper we address a theoretical calculation of the electronic spectra of an Si-Ge atomic chain that is arranged in a Fibonacci quasi-periodic sequence, by using a semi-empirical quantum method based on the Hueckel extended model. We apply the Fibonacci substitutional sequences in the atomic building blocks A(Si) and B(Ge) through the inflation rule or a recursion relation. In our ab initio calculations we use only a single point, which is sufficient for considering all the orbitals and charge distribution across the entire system. Although the calculations presented here are more complete than the models adopted in the literature which take into account the electronic interaction only up to the second and third neighbors, an interesting property remains in their electronic spectra: the fractality (which is the main signature of this kind of system). We discuss this fractality of the spectra and we compare them with the random arrangement of the Si-Ge atomic chain, and with previous results based on the tight-binding approximation of the Schroedinger equation considering up to the nearest neighbor. (paper)

  14. Electronic properties of Fibonacci and random Si-Ge chains.

    Science.gov (United States)

    Vasconcelos, M S; Azevedo, David L; Hadad, A; Galvão, D S

    2011-10-12

    In this paper we address a theoretical calculation of the electronic spectra of an Si-Ge atomic chain that is arranged in a Fibonacci quasi-periodic sequence, by using a semi-empirical quantum method based on the Hückel extended model. We apply the Fibonacci substitutional sequences in the atomic building blocks A(Si) and B(Ge) through the inflation rule or a recursion relation. In our ab initio calculations we use only a single point, which is sufficient for considering all the orbitals and charge distribution across the entire system. Although the calculations presented here are more complete than the models adopted in the literature which take into account the electronic interaction only up to the second and third neighbors, an interesting property remains in their electronic spectra: the fractality (which is the main signature of this kind of system). We discuss this fractality of the spectra and we compare them with the random arrangement of the Si-Ge atomic chain, and with previous results based on the tight-binding approximation of the Schrödinger equation considering up to the nearest neighbor.

  15. GeSi nanocrystals formed by high temperature annealing of GeO/SiO2 multilayers: structure and optical properties

    Science.gov (United States)

    Volodin, V. A.; Cherkov, A. G.; Vdovin, V. I.; Stoffel, M.; Rinnert, H.; Vergnat, M.

    2016-12-01

    The structural and optical properties of Ge and GeSi nanocrystals, formed by annealing of GeO/SiO2 multilayers have been investigated. According to Raman spectroscopy, the formation of pure Ge nanocrystals is observed after post growth annealing at 700 °C. Annealings at 800°C-900°C leads to the formation of intermixed GexSi1-x nanocrystals. High resolution transmission electron microscopy shows that the structure and the size of the nanocrystals strongly depend on annealing temperature. Spatial redistribution of Ge with the formation of large faceted clusters located near the Si substrate as well as GeSi intermixing at the substrate/film interface were observed. In the case of the sample containing 20 pairs of GeO/SiO2 layers annealed at 900 °C, some clusters exhibit a pyramid-like shape. FTIR absorption spectroscopy measurements demonstrate that intermixing between the GeO and SiO2 layers occurs leading to the formation of a SiGeO2 glass. Low temperature (10 K-100 K) photoluminescence was observed in the spectral range 1400-2000 nm for samples containing nanocrystals. The temperature dependence of the photoluminescence is studied.

  16. SiGe-on-insulator substrate fabricated by low energy oxygen implantation

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Yukari E-mail: yukari@jfcc.or.jp; Saito, T.; Shibata, N.; Fukatsu, S

    1999-01-01

    Nanometer order SiGe-on-insulator substrates have become accessible by using the separation-by-implanted-oxygen (SIMOX) technique. Low energy (25 keV) oxygen ion (O{sup +}) implantation was performed on a strain-relieved Si{sub 0.82}Ge{sub 0.18} substrate. The dose window for a SOI structure was found by cross-sectional imaging to be 2-2.5x10{sup 17} cm{sup -2}. The Ge composition of the top SiGe layer is controllable by post-implant annealing. Fabrication of SiGe-on-insulator substrates on a thick pseudomorphic Si{sub 0.82}Ge{sub 0.18} grown on Si(1 0 0) is also demonstrated. The results hold promise for a low-cost and high-throughput SiGe-SIMOX.

  17. Growth of one-dimensional Si/SiGe heterostructures by thermal CVD

    Energy Technology Data Exchange (ETDEWEB)

    Mouchet, Celine; Latu-Romain, Laurence; Rouviere, Emmanuelle; Celle, Caroline; Simonato, Jean-Pierre [CEA, LITEN, DTNM, LCH, 38054 Grenoble (France); Cayron, Cyril [CEA, LITEN, DTH, Grenoble Electron Microscopy at Minatec, 38054 Grenoble (France)], E-mail: jean-pierre.simonato@cea.fr

    2008-08-20

    The first results on a simple new process for the direct fabrication of one-dimensional superlattices using common CVD chambers are presented. The experiments were carried out in a 200 mm industrial Centura reactor (Applied Materials). Low dimensionality and superlattices allow a significant increase in the figure of merit of thermoelectrics by controlling the transport of phonons and electrons. The monocrystalline nanowires produced according to this process are both one-dimensional and present heterostructures, with very thin layers (40 nm) of Si and SiGe. Concentrations up to 30 at.% Ge were obtained in the SiGe parts. Complementary techniques including transmission electronic microscopy (TEM), selected area electron diffraction (SAED), energy dispersive x-ray spectroscopy (EDS), scanning transmission electron microscopy (STEM) in bright field and high angle annular dark field (HAADF STEM), and energy-filtered transmission electron microscopy (EF-TEM) were used to characterize the nanoheterostructures.

  18. Analysis of X-Ray Diffraction as a Probe of Interdiffusion in Si/SiGe Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Brennan, Sean M

    2003-08-20

    We investigate numerical simulations that utilize a non-linear interdiffusion solver and dynamical x-ray diffraction calculations to predict the local composition evolution in low Ge concentration Si/SiGe superlattices and their diffraction patterns during annealing. Superlattice satellite peak decay rates are compared with experimentally measured values and simulated diffraction patterns are matched directly to data with good success. The simulations are used to test the sensitivity of x-ray diffraction to various uncertainties commonly encountered when measuring interdiffusion at Si/SiGe interfaces. It is found that the most serious errors result from variations in the Ge content across the surface of the wafer. For example, the resolution limit of most experimental techniques used to measure Ge concentration in a SiGe film is -1 at.%, for a film with 11% mean Ge concentration annealed for 5 hours at 870 C, this level of error will cause the observed interdiffusivity values to deviate by -25% or +50%. The simulations are further used to show that for Si/SiGe interdiffusion, superlattice diffraction produces valid measurements when applied to 004 superlattice satellite peaks and square wave composition modulations even though it is only exactly applicable to satellite peaks about 000 reflection and to sinusoidal composition modulations. Finally, we show that proper interpretation of x-ray scattering data to extract Si/SiGe interdiffusivity values must account for the strong dependence of the interdiffusivity on Ge concentration.

  19. Potential of asymmetrical Si/Ge and Ge/Si based hetero-junction transit time devices over homo-junction counterparts for generation of high power

    Institute of Scientific and Technical Information of China (English)

    Moumita Mukherjee; Pravash R. Tripathy; S. P. Pati

    2011-01-01

    Static and dynamic properties of both complementary n-Ge/p-Si and p-Ge/n-Si hetero-junction DoubleDrift IMPATT diodes have been investigated by an advanced and realistic computer simulation technique,developed by the authors,for operation in the Ka-,V- and W-band frequencies.The results are further compared with corresponding Si and Ge homo-junction devices.The study shows high values of device efficiency,such as 23%,22% and 21.5%,for n-Ge/p-Si IMPATTs at the Ka,V and W bands,respectively.The peak device negative conductances for n-Si/p-Ge and n-Ge/p-Si hetero-junction devices found to be 50.7 × 106 S/m2 and 71.3 × 106 S/m2,which are ~3-4 times better than their Si and Ge counterparts at the V-band.The computed values of RF powerdensity for n-Ge/p-Si hetero-junction IMPATTs are 1.0 × 109,1.1 × 109 and 1.4 × 109 W/m2,respectively,for Ka-,V- and W-band operation,which can be observed to be the highest when compared with Si,Ge and n-Si/p-Ge devices.Both of the hetero-junctions,especially the n-Ge/p-Si hetero-junction diode,can thus become a superior RF-power generator over a wide range of frequencies.The present study will help the device engineers to choose a suitable material pair for the development of high-power MM-wave IMPATT for applications in the civil and defense-related arena.

  20. Magnetism and electronic structure of CoFeCrX (X = Si, Ge) Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Y.; O' Connell, A. [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); Kharel, P., E-mail: parashu.kharel@sdstate.edu [Department of Physics, South Dakota State University, Brookings, South Dakota 57007 (United States); Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States); Lukashev, P., E-mail: pavel.lukashev@uni.edu; Staten, B.; Tutic, I. [Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614 (United States); Valloppilly, S. [Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States); Herran, J. [Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, Iowa 50614 (United States); Mitrakumar, M.; Bhusal, B.; Huh, Y. [Department of Physics, South Dakota State University, Brookings, South Dakota 57007 (United States); Yang, K. [Department of Physics, South Dakota State University, Brookings, South Dakota 57007 (United States); College of Mechanical and Electrical Engineering, Hohai University, Changzhou (China); Skomski, R.; Sellmyer, D. J. [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States)

    2016-08-07

    The structural, electronic, and magnetic properties of CoFeCrX (X = Si, Ge) Heusler alloys have been investigated. Experimentally, the alloys were synthesized in the cubic L2{sub 1} structure with small disorder. The cubic phase of CoFeCrSi was found to be highly stable against heat treatment, but CoFeCrGe disintegrated into other new compounds when the temperature reached 402 °C (675 K). Although the first-principle calculation predicted the possibility of tetragonal phase in CoFeCrGe, the tetragonal phase could not be stabilized experimentally. Both CoFeCrSi and CoFeCrGe compounds showed ferrimagnetic spin order at room temperature and have Curie temperatures (T{sub C}) significantly above room temperature. The measured T{sub C} for CoFeCrSi is 790 K but that of CoFeCrGe could not be measured due to its dissociation into new compounds at 675 K. The saturation magnetizations of CoFeCrSi and CoFeCrGe are 2.82 μ{sub B}/f.u. and 2.78 μ{sub B}/f.u., respectively, which are close to the theoretically predicted value of 3 μ{sub B}/f.u. for their half-metallic phases. The calculated band gaps for CoFeCrSi and CoFeCrGe are, respectively, 1 eV and 0.5 eV. These materials have potential for spintronic device applications, as they exhibit half-metallic electronic structures with large band gaps, and Curie temperatures significantly above room temperature.

  1. Theory and design of quantum cascade lasers in (111) n -type Si/SiGe

    Science.gov (United States)

    Valavanis, A.; Lever, L.; Evans, C. A.; Ikonić, Z.; Kelsall, R. W.

    2008-07-01

    Although most work toward the realization of group IV quantum cascade lasers (QCLs) has focused on valence-band transitions, there are many desirable properties associated with the conduction band. We show that the commonly cited shortcomings of n -type Si/SiGe heterostructures can be overcome by moving to the (111) growth direction. Specifically, a large band offset and low effective mass are achievable and subband degeneracy is preserved. We predict net gain up to lattice temperatures of 90 K in a bound-to-continuum QCL with a double-metal waveguide, and show that a Ge interdiffusion length of at least 8Å across interfaces is tolerable.

  2. Superconducting single electron transistor for charge sensing in Si/SiGe-based quantum dots

    Science.gov (United States)

    Yang, Zhen

    Si-based quantum devices, including Si/SiGe quantum dots (QD), are promising candidates for spin-based quantum bits (quits), which are a potential platform for quantum information processing. Meanwhile, qubit readout remains a challenging task related to semiconductor-based quantum computation. This thesis describes two readout devices for Si/SiGe QDs and the techniques for developing them from a traditional single electron transistor (SET). By embedding an SET in a tank circuit and operating it in the radio-frequency (RF) regime, a superconducting RF-SET has quick response as well as ultra high charge sensitivity and can be an excellent charge sensor for the QDs. We demonstrate such RF-SETs for QDs in a Si/SiGe heterostructure. Characterization of the SET in magnetic fields is studied for future exploration of advanced techniques such as spin detection and spin state manipulation. By replacing the tank circuit with a high-quality-factor microwave cavity, the embedded SET will be operated in the supercurrent regime as a single Cooper pair transistor (CPT) to further increase the charge sensitivity and reduce any dissipation. The operating principle and implementation of the cavity-embedded CPT (cCPT) will be introduced.

  3. A high performance Ge/Si0.5Ge0.5/Si heterojunction dual sources tunneling transistor with a U-shaped channel

    Science.gov (United States)

    Li, Wei; Liu, Hongxia; Wang, Shulong; Wang, Qianqiong; Chen, Shupeng

    2017-06-01

    In this paper, a new Ge/Si0.5Ge0.5/Si heterojunction dual sources tunneling transistor with a U-shaped channel (Ge_DUTFET) is proposed and investigated by Silvaco-Atlas simulation. The line tunneling perpendicular to channel and point tunneling parallel to channel simultaneously occur on both sides of the gate. The Ge is chosen as the source region material to increase the line tunneling current. The designed heterojunction between the Ge source and Si channel decreases the point tunneling barrier width to enhance the point tunneling current. And this heterojunction can also promote the Ge_DUTFET to occur point tunneling at the small gate voltage, which makes it obtain the smaller turn-on voltage. Furthermore, the Si0.5Ge0.5 buffer layer is also helpful for the enhancement of performance. The simulation results reveal that Ge_DUTFET has the better performance compared with the Si_DUTFET. The on-state current and average subthreshold swing of Ge_DUTFET are 1.11 × 10-5A/μm and 35.1mV/dec respectively. The max cut-off frequency (fT) and gain bandwidth product (GBW) are 26.6 GHz and 16.6 GHz respectively. The fT and GBW of the Ge_DUTFET are respectively increased by ∼27.4% and ∼84.3% compared with the Si_DUTFET.

  4. Templated self-assembly of SiGe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Dais, Christian

    2009-08-19

    This PhD thesis reports on the fabrication and characterization of exact aligned SiGe quantum dot structures. In general, SiGe quantum dots which nucleate via the Stranski-Krastanov growth mode exhibit broad size dispersion and nucleate randomly on the surface. However, to tap the full potential of SiGe quantum dots it is necessary to control the positioning and size of the dots on a nanometer length, e.g. for electronically addressing of individual dots. This can be realized by so-called templated self-assembly, which combines top-down lithography with bottom-up selfassembly. In this process the lithographically defined pits serve as pre-defined nucleation points for the epitaxially grown quantum dots. In this thesis, extreme ultraviolet interference lithography at a wavelength of e=13.4 nm is employed for prepatterning of the Si substrates. This technique allows the precise and fast fabrication of high-resolution templates with a high degree of reproducibility. The subsequent epitaxial deposition is either performed by molecular beam epitaxy or low-pressure chemical vapour deposition. It is shown that the dot nucleation on pre-patterned substrates depends strongly on the lithography parameters, e.g. size and periodicity of the pits, as well as on the epitaxy parameters, e.g. growth temperature or material coverage. The interrelations are carefully analyzed by means of scanning force microscopy, transmission electron microscopy and X-ray diffraction measurements. Provided that correct template and overgrowth parameters are chosen, perfectly aligned and uniform SiGe quantum dot arrays of different period, size as well as symmetry are created. In particular, the quantum dot arrays with the so far smallest period (35 nm) and smallest size dispersion are fabricated in this thesis. Furthermore, the strain fields of the underlying quantum dots allow the fabrication of vertically aligned quantum dot stacks. Combining lateral and vertical dot alignment results in three

  5. Magnetocaloric effect of Gd5Si2Ge2 alloys in low magnetic field

    Indian Academy of Sciences (India)

    Hong Zeng; Chunjiang Kuang; Jiuxing Zhang; Ming Yue

    2011-07-01

    The magnetocaloric effect of Gd5Si2Ge2 alloys under heat treatment conditions are investigated in low magnetic fields. The magnetocaloric effect (MCE) is studied by measuring magnetic entropy change ( M) and adiabatic temperature change ( ad) in a magnetic field of 1.5 T using a vibrating sample magnetometer (VSM) and a home-made magnetocaloric effect measuring apparatus, respectively. The maximum M of the alloys increases by 200% from 4.38 to 13.32 J kg-1 K-1, the maximum ad increases by 105% from 1.9 to 3.9 K when compared to the as-cast due to the homogeneous composition distribution and microstructure, while the magnetic ordering temperature is slightly reduced. These results indicate that the annealed Gd5Si2Ge2 compounds are promising as high-performance magnetic refrigerants working room temperature in relatively low magnetic fields.

  6. Low-temperature reduction of Ge oxide by Si and SiH4 in low-pressure H2 and Ar environment

    Science.gov (United States)

    Minami, Kaichiro; Moriya, Atsushi; Yuasa, Kazuhiro; Maeda, Kiyohiko; Yamada, Masayuki; Kunii, Yasuo; Niwano, Michio; Murota, Junichi

    2015-08-01

    Introduction of Ge into ULSIs has become increasingly attractive because of the higher carrier mobility of Ge. Since Ge native oxide is formed easily in cleanroom air, the control of formation and reduction of the Ge oxide is requested for the introduction of Ge layers into Si process. Here, the reactions between gas phase Ge oxide and Si substrate and between the Ge oxide on Ge epitaxial layer and SiH4 are investigated. The native-oxidized Ge amount is obtained by calculating from chemically shifted peak intensity of Ge 3d measured by X-ray photoelectron spectroscopy. By the adsorption of the Ge oxide on Si(1 0 0) surface, pure Ge and Si oxide are formed on the Si surface even at 350 °C and the formed Ge amount tends to correspond to the oxidized Si amount, independently of the heat-treatment environment of H2 and Ar under the condition that Si oxide is not reduced by H2. By SiH4 treatment, the amount of the oxidized Ge on the Ge layer decreases drastically even at 350 °C and Si oxide is formed on the Ge layer. From these results, it is suggested that the Ge oxide is reduced even at 350 °C by Si or SiH4, and the Si oxide and the pure Ge are formed.

  7. Magnetism of carbon doped Mn5Si3 and Mn5Ge3 films

    Indian Academy of Sciences (India)

    C Sürgers; K Potzger; G Fischer

    2009-03-01

    The magnetic properties of Mn5Si3C and Mn5Ge3C films prepared by magnetron cosputtering or C+-ion implantation are studied. The carbon-doped films exhibit ferromagnetic properties with Curie temperatures C well above room temperature and metallic conductivity, making them possible candidates for future magnetic semiconductor-based devices. In Mn5Si3C, the carbon gives rise to a lattice expansion and a concomitant change of the magnetic order from antiferromagnetic Mn5Si3 to ferromagnetic Mn5Si3C0.8 with C = 350 K. Likewise, C of ferromagnetic Mn5Ge3 is strongly enhanced in Mn5Ge3C0.8. However, in this case the lattice is slightly compressed by carbon. This demonstrates that the effect of carbon on the magnetic behaviour in these compounds is not simply due to a change of the various interatomic distances by carbon but also due to a modification of the electronic band structure.

  8. Thermally induced strain relaxation in SiGe/Si heterostructures with low-temperature buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Vdovin, V.I.; Mil' vidskii, M.G. [Institute for Chemical Problems of Microelectronics, 119017 Moscow (Russian Federation); Yugova, T.G. [Institute of Rare Metals ' Giredmet' , 119017 Moscow (Russian Federation); Rzaev, M.M. [Lebedev Physical Institute, RAS, 119991 Moscow (Russian Federation); Schaeffler, F. [Institut fuer Halbleiter- und Festkoerperphysik, 4040 Linz (Austria)

    2005-04-01

    Processes of misfit dislocation (MD) nucleation and multiplication in SiGe/Si strained-layer heterostructures under thermal annealing were studied. Specific subjects include the kinetics of dislocation network formation in heterostructures with low-temperature (LT) buffer layers and mechanisms of dislocation nucleation. Samples with LT-Si (400 C) and LT-SiGe (250 C) buffer layers were grown by MBE. In general, the processes of MD generation occur similarly in the heterostructures studied independently of the alloy composition (Ge content: 0.15, 0.30) and kind of buffer layer. Intrinsic point defects related to the LT epitaxial growth influence mainly the rate of MD nucleation. We suggest a new mechanism of MD generation which includes a nucleation of incipient dislocation loops at heterogeneous sources within SiGe epitaxial layer and formation of spiral sources at threading V-shaped dislocation half-loops. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. The Effects of Annealing Temperatures on Composition and Strain in SixGe1−x Obtained by Melting Growth of Electrodeposited Ge on Si (100

    Directory of Open Access Journals (Sweden)

    Mastura Shafinaz Zainal Abidin

    2014-02-01

    Full Text Available The effects of annealing temperatures on composition and strain in SixGe1−x, obtained by rapid melting growth of electrodeposited Ge on Si (100 substrate were investigated. Here, a rapid melting process was performed at temperatures of 1000, 1050 and 1100 °C for 1 s. All annealed samples show single crystalline structure in (100 orientation. A significant appearance of Si-Ge vibration mode peak at ~400 cm−1 confirms the existence of Si-Ge intermixing due to out-diffusion of Si into Ge region. On a rapid melting process, Ge melts and reaches the thermal equilibrium in short time. Si at Ge/Si interface begins to dissolve once in contact with the molten Ge to produce Si-Ge intermixing. The Si fraction in Si-Ge intermixing was calculated by taking into account the intensity ratio of Ge-Ge and Si-Ge vibration mode peaks and was found to increase with the annealing temperatures. It is found that the strain turns from tensile to compressive as the annealing temperature increases. The Si fraction dependent thermal expansion coefficient of SixGe1−x is a possible cause to generate such strain behavior. The understanding of compositional and strain characteristics is important in Ge/Si heterostructure as these properties seem to give significant effects in device performance.

  10. Effect of asymmetric concentration profile on thermal conductivity in Ge/SiGe superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, Konstanze R., E-mail: konstanze.hahn@dsf.unica.it [Department of Physics, University of Cagliari, Cittadella Universitaria, 09042 Monserrato (Italy); Cecchi, Stefano [Department of Epitaxy, Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Colombo, Luciano [Department of Physics, University of Cagliari, Cittadella Universitaria, 09042 Monserrato (Italy); Institut de Cieǹcia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, 08193 Barcelona (Spain); Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, 08193 Barcelona (Spain)

    2016-05-16

    The effect of the chemical composition in Si/Ge-based superlattices on their thermal conductivity has been investigated using molecular dynamics simulations. Simulation cells of Ge/SiGe superlattices have been generated with different concentration profiles such that the Si concentration follows a step-like, a tooth-saw, a Gaussian, and a gamma-type function in direction of the heat flux. The step-like and tooth-saw profiles mimic ideally sharp interfaces, whereas Gaussian and gamma-type profiles are smooth functions imitating atomic diffusion at the interface as obtained experimentally. Symmetry effects have been investigated comparing the symmetric profiles of the step-like and the Gaussian function to the asymmetric profiles of the tooth-saw and the gamma-type function. At longer sample length and similar degree of interdiffusion, the thermal conductivity is found to be lower in asymmetric profiles. Furthermore, it is found that with smooth concentration profiles where atomic diffusion at the interface takes place the thermal conductivity is higher compared to systems with atomically sharp concentration profiles.

  11. Effect of asymmetric concentration profile on thermal conductivity in Ge/SiGe superlattices

    Science.gov (United States)

    Hahn, Konstanze R.; Cecchi, Stefano; Colombo, Luciano

    2016-05-01

    The effect of the chemical composition in Si/Ge-based superlattices on their thermal conductivity has been investigated using molecular dynamics simulations. Simulation cells of Ge/SiGe superlattices have been generated with different concentration profiles such that the Si concentration follows a step-like, a tooth-saw, a Gaussian, and a gamma-type function in direction of the heat flux. The step-like and tooth-saw profiles mimic ideally sharp interfaces, whereas Gaussian and gamma-type profiles are smooth functions imitating atomic diffusion at the interface as obtained experimentally. Symmetry effects have been investigated comparing the symmetric profiles of the step-like and the Gaussian function to the asymmetric profiles of the tooth-saw and the gamma-type function. At longer sample length and similar degree of interdiffusion, the thermal conductivity is found to be lower in asymmetric profiles. Furthermore, it is found that with smooth concentration profiles where atomic diffusion at the interface takes place the thermal conductivity is higher compared to systems with atomically sharp concentration profiles.

  12. Photoreflectance Spectroscopy Characterization of Ge/Si0.16Ge0.84 Multiple Quantum Wells on Ge Virtual Substrate

    Directory of Open Access Journals (Sweden)

    Hung-Pin Hsu

    2013-01-01

    Full Text Available We report a detailed characterization of a Ge/Si0.16Ge0.84 multiple quantum well (MQW structure on Ge-on-Si virtual substrate (VS grown by ultrahigh vacuum chemical vapor deposition by using temperature-dependent photoreflectance (PR in the temperature range from 10 to 300 K. The PR spectra revealed a wide range of optical transitions from the MQW region as well as transitions corresponding to the light-hole and heavy-hole splitting energies of Ge-on-Si VS. A detailed comparison of PR spectral line shape fits and theoretical calculation led to the identification of various quantum-confined interband transitions. The temperature-dependent PR spectra of Ge/Si0.16Ge0.84 MQW were analyzed using Varshni and Bose-Einstein expressions. The parameters that describe the temperature variations of various quantum-confined interband transition energies were evaluated and discussed.

  13. Ultra-smooth epitaxial Ge grown on Si(001) utilizing a thin C-doped Ge buffer layer

    KAUST Repository

    Mantey, J.

    2013-01-01

    Here, we present work on epitaxial Ge films grown on a thin buffer layer of C doped Ge (Ge:C). The growth rate of Ge:C is found to slow over time and is thus unsuitable for thick (>20 nm) layers. We demonstrate Ge films from 10 nm to >150 nm are possible by growing pure Ge on a thin Ge:C buffer. It is shown that this stack yields exceedingly low roughness levels (comparable to bulk Si wafers) and contains fewer defects and higher Hall mobility compared to traditional heteroepitaxial Ge. The addition of C at the interface helps reduce strain by its smaller atomic radius and its ability to pin defects within the thin buffer layer that do not thread to the top Ge layer. © 2013 AIP Publishing LLC.

  14. Coherently Strained Si-SixGe1-x Core-Shell Nanowire Heterostructures.

    Science.gov (United States)

    Dillen, David C; Wen, Feng; Kim, Kyounghwan; Tutuc, Emanuel

    2016-01-13

    Coherently strained Si-SixGe1-x core-shell nanowire heterostructures are expected to possess a positive shell-to-core conduction band offset, allowing for quantum confinement of electrons in the Si core. We report the growth of epitaxial, coherently strained Si-SixGe1-x core-shell heterostructures through the vapor-liquid-solid mechanism for the Si core, followed in situ by the epitaxial SixGe1-x shell growth using ultrahigh vacuum chemical vapor deposition. The Raman spectra of individual nanowires reveal peaks associated with the Si-Si optical phonon mode in the Si core and the Si-Si, Si-Ge, and Ge-Ge vibrational modes of the SixGe1-x shell. The core Si-Si mode displays a clear red-shift compared to unstrained, bare Si nanowires thanks to the lattice mismatch-induced tensile strain, in agreement with calculated values using a finite-element continuum elasticity model combined with lattice dynamic theory. N-type field-effect transistors using Si-SixGe1-x core-shell nanowires as channel are demonstrated.

  15. Si/SiGe bound-to-continuum quantum cascade terahertz emitters

    Science.gov (United States)

    Paul, D. J.; Matmon, G.; Lever, L.; Ikonić, Z.; Kelsall, R. W.; Chrastina, D.; Isella, G.; von Känel, H.

    2008-04-01

    A review will be presented of recent work on Si/SiGe heavy-hole to heavy-hole quantum cascade emitters showing progress towards a laser using the bound-to-continuum design for the active region. The sample was grown by low energy plasma enhanced chemical vapour deposition in significantly less time than comparable structures and designs in III-V or Si/SiGe technology using molecular beam epitaxy or more standard chemical vapour deposition techniques. Clear intersubband electroluminescence is demonstrated at 4.2 K between 6.7 and 10.1 THz. This is inside the III-V restrahlung band where III-V materials cannot lase, unlike Group IV materials. A review of waveguide losses will also be presented and some ideas of how to design an active region with gain higher than the waveguide losses will be discussed.

  16. Vertical Ge/Si Core/Shell Nanowire Junctionless Transistor.

    Science.gov (United States)

    Chen, Lin; Cai, Fuxi; Otuonye, Ugo; Lu, Wei D

    2016-01-13

    Vertical junctionless transistors with a gate-all-around (GAA) structure based on Ge/Si core/shell nanowires epitaxially grown and integrated on a ⟨111⟩ Si substrate were fabricated and analyzed. Because of efficient gate coupling in the nanowire-GAA transistor structure and the high density one-dimensional hole gas formed in the Ge nanowire core, excellent P-type transistor behaviors with Ion of 750 μA/μm were obtained at a moderate gate length of 544 nm with minimal short-channel effects. The experimental data can be quantitatively modeled by a GAA junctionless transistor model with few fitting parameters, suggesting the nanowire transistors can be fabricated reliably without introducing additional factors that can degrade device performance. Devices with different gate lengths were readily obtained by tuning the thickness of an etching mask film. Analysis of the histogram of different devices yielded a single dominate peak in device parameter distribution, indicating excellent uniformity and high confidence of single nanowire operation. Using two vertical nanowire junctionless transistors, a PMOS-logic inverter with near rail-to-rail output voltage was demonstrated, and device matching in the logic can be conveniently obtained by controlling the number of nanowires employed in different devices rather than modifying device geometry. These studies show that junctionless transistors based on vertical Ge/Si core/shell nanowires can be fabricated in a controlled fashion with excellent performance and may be used in future hybrid, high-performance circuits where bottom-up grown nanowire devices with different functionalities can be directly integrated with an existing Si platform.

  17. Strain-induced morphology manipulations of Si and Ge-based heterostructures on Si(0 0 1) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dentel, D.; Aiet-Mansour, K.; Bischoff, J.L.; Kubler, L.; Bolmont, D

    2004-07-31

    By using reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM) analyses, we show that the well-known Stranski-Krastanov growth mode of Ge/Si(0 0 1) can be modified in a Volmer-Weber one by C pre-deposition on the Si(0 0 1) surface or in a Frank-Van der Merve one by supplying atomic hydrogen during the Ge growth. By tuning the growth conditions and acting on the interplay of surface diffusion, strain and surface energy, morphology manipulations by the growth process control are therefore possible. The Si capping of these Ge self-assembled nanostructures also allows us to point out a correlation between the nucleation mechanism of the Ge or SiGe islands and their associated embedding process. On bare Si surfaces, the final morphology of the embedded Ge film is strongly dependent on the kinetic parameters of the capping layer. Indeed oriented migrations of both Si and Ge atoms are able to smooth or to maintain the islands on the surface. Si diffusions also contribute in a rapid restoration of a planar morphology. On Si(0 0 1)-c(4 x 4) the adatom migrations and consequently the covering mechanism of the Ge islands seems to be governed by the strain mapping related to the C pre-deposited surface. The first stages of the Si capping process have revealed the preservation of the Ge islands associated to an increase of the surface roughness.

  18. Waveguide design for mid- and far-infrared p-Si/SiGe quantum cascade lasers

    Science.gov (United States)

    Ikonic, Z.; Kelsall, R. W.; Harrison, P.

    2004-01-01

    Design considerations are presented for waveguides to be used in p-Si/SiGe based quantum cascade lasers operating in the mid- and far-infrared wavelength ranges. Modal losses and confinement factors are calculated for both TM and TE modes in conventional double metal clad structures, metal-highly doped semiconductor layer structures and also in novel metal-metal silicide structures. Guidelines for choosing the confinement and contact layer parameters are given.

  19. Photoluminescence enhancement in double Ge/Si quantum dot structures

    Science.gov (United States)

    Zinovieva, A. F.; Zinovyev, V. A.; Nikiforov, A. I.; Timofeev, V. A.; Mudryi, A. V.; Nenashev, A. V.; Dvurechenskii, A. V.

    2016-12-01

    Luminescence properties of double Ge/Si quantum dot structures were studied at liquid helium temperature depending on the Si spacer thickness d in QD molecules. A seven-fold increase of the integrated photoluminescence intensity was obtained for the structures with optimal thickness d = 2 nm. This enhancement is explained by increasing the overlap integral of electron and hole wave functions. Two main factors promote this increasing. The first one is that the electrons are localized at the QD base edges and their wave functions are the linear combinations of the states of in-plane Δ valleys, which are perpendicular in k-space to the growth direction [001]. This results in the increasing probability of electron penetration into Ge barriers. The second factor is the arrangement of Ge nanoclusters in closely spaced QD groups. The strong tunnel coupling of QDs within these groups increases the probability of hole finding at the QD base edge, that also promotes the increase of the radiative recombination probability.

  20. Structural, elastic constants, hardness, and optical properties of pyrite-type dinitrides (CN 2, SiN 2, GeN 2)

    Science.gov (United States)

    Ding, Y. C.; Xiang, A. P.; He, X. J.; Hu, X. F.

    2011-04-01

    The crystal structures, band structures, elastic constants, hardness, and optical properties of pyrite-type dinitrides (CN 2, SiN 2, and GeN 2) are obtained from the density functional theory using the plane-wave pseudopotential (PWP) method within the local density and generalized gradient approximations. The formation enthalpies for AN 2 (A=C, Si, and Ge) compounds suggest the three structures that are stable. The calculated band structures show the indirect gaps ( Γ-R) in CN 2, SiN 2, and GeN 2. The intrinsic hardnesses of AN 2 (A=C, Si, and Ge ) compounds are calculated. Our results show that the cubic CN 2 and SiN 2 are superhard materials. Furthermore, we studied the optical properties such as the complex dielectric function and the electron energy loss spectra.

  1. Thermal oxidation of Si/SiGe heterostructures for use in quantum dot qubits

    Science.gov (United States)

    Neyens, Samuel F.; Foote, Ryan H.; Knapp, T. J.; McJunkin, Thomas; Savage, D. E.; Lagally, M. G.; Coppersmith, S. N.; Eriksson, M. A.

    Here we demonstrate dry thermal oxidation of a Si/SiGe heterostructure at 700°C and use a Hall bar device to measure the mobility after oxidation to be 43,000 cm2V-1s-1 at a carrier density of 4.1 ×1011 cm-2. Surprisingly, we find no significant reduction in mobility compared with an Al2O3 device made with atomic layer deposition on the same heterostructure, indicating thermal oxidation can be used to process Si/SiGe quantum dot devices. This result provides a path for investigating improvements to the gate oxide in Si/SiGe qubit devices, whose performance is believed to be limited by charge noise in the oxide layer. This work was supported in part by ARO (W911NF-12-0607) and NSF (DMR-1206915 and PHY-1104660). Development and maintenance of the growth facilities used for fabricating samples is supported by DOE (DE-FG02-03ER46028). This research utilized NSF-supported shared facilities at the University of Wisconsin-Madison.

  2. The effect of donors on lateral gated quantum-devices in Si/SiGe heterostructures

    Science.gov (United States)

    Lin, Xi; Hu, Jingshi; Lai, A.; Zhang, Z.; Maclean, K.; Xie, Y. H.; Kastner, M. A.

    2011-03-01

    Much activity has focused on the development of quantum dots in Si/SiGe because of its potentially very long decoherence times (T2). However, to fabricate well-controlled quantum dots in Si/SiGe heterostructures, one must overcome complications that do not arise in GaAs/AlGaAs heterostructures. We demonstrate that switching charge noise and donor-layer conduction can lead to instability and cross-coupling among the tunnel barriers, thus making it difficult to achieve highly stable and tunable quantum devices in a Si/SiGe heterostructure. In particular, we have used an integrated charge-sensing quantum point contact to investigate the charge motion that originates from the excess donors, and present a systematic capacitance measurement to show how the donor layer affects device function in devices with large (~ 100 μ m 2) gates as well as nanometer-size ones. This work has been supported by the Nanoscale Science and Engineering Center program of NSF (PHY-0117795), NSF (DMR-0701386).

  3. Self-assembled strained GeSiSn nanoscale structures grown by MBE on Si(100)

    Science.gov (United States)

    Nikiforov, A. I.; Timofeev, V. A.; Tuktamyshev, A. R.; Yakimov, A. I.; Mashanov, V. I.; Gutakovskii, A. K.

    2017-01-01

    Gradual relaxation of elastic deformations in a silicon layer at the growth of a covering layer on strained layers was established. The dependence of the thickness of a silicon film, where full elastic strain relaxation occurs, on the germanium layer thickness was determined. The dependence of the critical thickness of 2D-3D transition of temperature and composition of the GeSiSn film on Si(100) was studied. Regularities of the formation of multilayer structures on quantum wells comprising pseudomorphous GeSiSn layers without relaxed buffer layers but creating the structures directly on Si. A possibility of synthesizing multilayer structures by molecular beam epitaxy was shown, and the crystal lattice constants using the high-resolution transmission electron microscopy were determined. Based on multilayer GeSiSn/Si structures the p-i-n-diodes, which demonstrated the photoresponse increasing by several orders of magnitude compared to the Sn-free structures at an increase in the Sn content, were created.

  4. Tunable thermal hysteresis in MnFe(P,Ge) compounds

    NARCIS (Netherlands)

    Trung, N.T.; Ou, Z.Q.; Gortenmulder, T.J.; Tegus, O.; Buschow, K.H.J.; Brück, E.

    2009-01-01

    Structural, magnetic, and magnetocaloric properties of the MnFe(P,Ge) compounds were systematically studied on both bulk alloys and melt-spun ribbons. The experimental results show that the critical behavior of the phase transition can be controlled by changing either the compositions or the anneali

  5. Tunable thermal hysteresis in MnFe(P,Ge) compounds

    NARCIS (Netherlands)

    Trung, N.T.; Ou, Z.Q.; Gortenmulder, T.J.; Tegus, O.; Buschow, K.H.J.; Brück, E.

    2009-01-01

    Structural, magnetic, and magnetocaloric properties of the MnFe(P,Ge) compounds were systematically studied on both bulk alloys and melt-spun ribbons. The experimental results show that the critical behavior of the phase transition can be controlled by changing either the compositions or the anneali

  6. Origin and removal of stacking faults in Ge islands nucleated on Si within nanoscale openings in SiO2

    Science.gov (United States)

    Leonhardt, Darin; Ghosh, Swapnadip; Han, Sang M.

    2011-10-01

    We have previously reported that Ge films formed after nucleation of Ge islands within nanometer size openings in SiO2 and their subsequent coalescence over the SiO2 template exhibit threading dislocation densities below 106 cm-2. However, these films contain a density of twin/stacking fault defects on the order of 5 × 1010 cm-2 that emanate primarily from the Ge-SiO2 interface. Most of these faults self-terminate within 200 nm of the interface; however, a total of 5 × 107 cm-2 propagate to the Ge surface. These defects are found to be detrimental to the morphology and minority carrier lifetime in III-V films integrated onto the Ge-on-Si virtual substrates. We have found that annealing the Ge islands during the initial stage of coalescence eliminates stacking faults, but further Ge growth leads to a film containing a threading dislocation density of 5 × 107 cm-2. To explain the origin of the twin/stacking fault defects in the Ge films and their removal after annealing Ge islands, we have studied the Ge islands before and after annealing. Our results indicate that twin/stacking faults originate from Ge islands that nucleate within nanoscale windows in the SiO2 template, in twin relationship to the underlying Si, and their coalescence with other epitaxial Ge islands. The density of Ge islands in twin relationship is approximately 4 × 1010 cm-2. In addition to the twin-oriented Ge islands, we observe that another group of Ge islands on the order of 2 × 1010 cm-2 have a small tilt-misorientation to the underlying Si ranging from 1.8 to 5.6°. After annealing, the density of both epitaxial and twin-oriented Ge islands is significantly reduced, and only the tilt-misoriented islands remain. The reduction in epitaxial and twin-oriented Ge islands stems from the thermal desorption of SiO2 template during the annealing, which leads to the transfer of Ge by surface diffusion from these Ge islands to the freshly exposed Si. This surface diffusion, while causing

  7. Experimental evidence of improved thermoelectric properties at 300K in Si/Ge superlattice structures

    Energy Technology Data Exchange (ETDEWEB)

    Venkatasubramanian, R.; Colpitts, T.; Watko, E.; Malta, D. [Research Triangle Inst., Research Triangle Park, NC (United States)

    1997-04-01

    The authors have found that it may be possible to obtain significant enhancement in ZT at 300 K, over conventional bulk SiGe alloys, through the use of Si/Ge Superlattice (SL) structures. The Seebeck coefficient in Si/Ge SL structures was observed to increase rapidly with decreasing SL period with no loss of electrical conductivity. The carrier mobilities in Si/Ge SLs were higher than in a comparable thin-film Si/Ge alloy. The best power factor of the short-period Si/Ge SLs is 112.2 {micro}W/K{sup 2} cm, over five-fold better than state-of-the-art n-type, bulk SiGe alloys. Approximately a two to four-fold reduction in thermal conductivity in short-period SL structures, compared to bulk SiGe alloy, was observed. The authors estimate at least a factor of five improvement over current state-of-the-art SiGe alloys, in several Si/Ge SL samples with periodicity of {approximately}45 to 75 {angstrom}. The results of this study are promising, but tentative due to the possible effects of substrate and the developmental nature of the thermoelectric property measurements.

  8. Enhanced relaxation of strained Ge{sub x}Si{sub 1-x} layers induced by Co/Ge{sub x}Si{sub 1-x} thermal reaction

    Energy Technology Data Exchange (ETDEWEB)

    Ridgway, M.C.; Elliman, R.G.; Rao, M.R. [Australian National Univ., Canberra, ACT (Australia); Baribeau, J.M. [National Research Council of Canada, Ottawa, ON (Canada)

    1993-12-31

    Enhanced relaxation of strained Ge{sub x}Si{sub l-x} layers during the formation of CoSi{sub 2} by Co/Ge{sub x}Si{sub 1-x} thermal reaction has been observed. Raman spectroscopy and transmission electron microscopy were used to monitor the extent of relaxation. Possible mechanisms responsible for the enhanced relaxation, including metal-induced dislocation nucleation, chemical and/or structural inhomogeneities at the reacted layer/Ge{sub x}Si{sub 1-x} interface and point defect injection due to silicide formation will be discussed. Also, methodologies for inhibiting relaxation will be presented. 11 refs., 1 fig.

  9. Infrared photoluminescence from GeSi nanocrystals embedded in a germanium–silicate matrix

    Energy Technology Data Exchange (ETDEWEB)

    Volodin, V. A., E-mail: volodin@isp.nsc.ru; Gambaryan, M. P.; Cherkov, A. G.; Vdovin, V. I. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Stoffel, M.; Rinnert, H.; Vergnat, M. [Université de Lorraine, Institut Jean Lamour UMR CNRS 7198 (France)

    2015-12-15

    We investigate the structural and optical properties of GeO/SiO{sub 2} multilayers obtained by evaporation of GeO{sub 2} and SiO{sub 2} powders under ultrahigh vacuum conditions on Si(001) substrates. Both Raman and infrared absorption spectroscopy measurements indicate the formation of GeSi nanocrystals after postgrowth annealing at 800°C. High-resolution transmission electron microscopy characterizations show that the average size of the nanocrystals is about 5 nm. For samples containing GeSi nanocrystals, photoluminescence is observed at 14 K in the spectral range 1500–1600 nm. The temperature dependence of the photoluminescence is studied.

  10. Infrared photoluminescence from GeSi nanocrystals embedded in a germanium-silicate matrix

    Science.gov (United States)

    Volodin, V. A.; Gambaryan, M. P.; Cherkov, A. G.; Vdovin, V. I.; Stoffel, M.; Rinnert, H.; Vergnat, M.

    2015-12-01

    We investigate the structural and optical properties of GeO/SiO2 multilayers obtained by evaporation of GeO2 and SiO2 powders under ultrahigh vacuum conditions on Si(001) substrates. Both Raman and infrared absorption spectroscopy measurements indicate the formation of GeSi nanocrystals after postgrowth annealing at 800°C. High-resolution transmission electron microscopy characterizations show that the average size of the nanocrystals is about 5 nm. For samples containing GeSi nanocrystals, photoluminescence is observed at 14 K in the spectral range 1500-1600 nm. The temperature dependence of the photoluminescence is studied.

  11. High Quality SiGe Layer Deposited by a New Ultrahigh Vacuum Chemical Vapor Deposition System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    An ultrahigh vacuum chemical vapor deposition (UHV/CVD) system is developed and the details of its construction and operation are reported. Using high purity SiH4 and GeH4 reactant gases,the Si0.82Ge0.18 layer is deposited at 550℃. With the measurements by double crystal X-ray diffraction (DCXRD), transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy (RBS) techniques, it is shown that the crystalline quality of the SiGe layer is good,and the underlying SiGe/Si heterointerface is sharply defined.

  12. Ge/SiGe quantum confined Stark effect electro-absorption modulation with low voltage swing at λ = 1550 nm.

    Science.gov (United States)

    Dumas, D C S; Gallacher, K; Rhead, S; Myronov, M; Leadley, D R; Paul, D J

    2014-08-11

    Low-voltage swing (≤1.0 V) high-contrast ratio (6 dB) electro-absorption modulation covering 1460 to 1560 nm wavelength has been demonstrated using Ge/SiGe quantum confined Stark effect (QCSE) diodes grown on a silicon substrate. The heterolayers for the devices were designed using an 8-band k.p Poisson-Schrödinger solver which demonstrated excellent agreement with the experimental results. Modelling and experimental results demonstrate that by changing the quantum well width of the device, low power Ge/SiGe QCSE modulators can be designed to cover the S- and C-telecommunications bands.

  13. Long Spin Relaxation and Coherence Times of Electrons In Gated Si/SiGe Quantum Dots

    Science.gov (United States)

    He, Jianhua; Tyryshkin, A. M.; Lyon, S. A.; Lee, C.-H.; Huang, S.-H.; Liu, C. W.

    2012-02-01

    Single electron spin states in semiconductor quantum dots are promising candidate qubits. We report the measurement of 250 μs relaxation (T1) and coherence (T2) times of electron spins in gated Si/SiGe quantum dots at 350 mK. The experiments used conventional X-band (10 GHz) pulsed electron spin resonance (pESR), on a large area (3.5 x 20 mm^2) dual-gate undoped high mobility Si/SiGe heterostructure sample, which was patterned with 2 x 10^8 quantum dots using e-beam lithography. Dots having 150 nm radii with a 700 nm period are induced in a natural Si quantum well by the gates. The measured T1 and T2 at 350 mK are much longer than those of free 2D electrons, for which we measured T1 to be 10 μs and T2 to be 6.5 μs in this gated sample. The results provide direct proof that the effects of a fluctuating Rashba field have been greatly suppressed by confining the electrons in quantum dots. From 0.35 K to 0.8 K, T1 of the electron spins in the quantum dots shows little temperature dependence, while their T2 decreased to about 150 μs at 0.8 K. The measured 350 mK spin coherence time is 10 times longer than previously reported for any silicon 2D electron-based structures, including electron spins confined in ``natural quantum dots'' formed by potential disorder at the Si/SiO2ootnotetextS. Shankar et al., Phys. Rev. B 82, 195323 (2010) or Si/SiGe interface, where the decoherence appears to be controlled by spin exchange.

  14. Light harvesting with Ge quantum dots embedded in SiO2 or Si3N4

    Science.gov (United States)

    Cosentino, Salvatore; Sungur Ozen, Emel; Raciti, Rosario; Mio, Antonio M.; Nicotra, Giuseppe; Simone, Francesca; Crupi, Isodiana; Turan, Rasit; Terrasi, Antonio; Aydinli, Atilla; Mirabella, Salvo

    2014-01-01

    Germanium quantum dots (QDs) embedded in SiO2 or in Si3N4 have been studied for light harvesting purposes. SiGeO or SiGeN thin films, produced by plasma enhanced chemical vapor deposition, have been annealed up to 850 °C to induce Ge QD precipitation in Si based matrices. By varying the Ge content, the QD diameter can be tuned in the 3-9 nm range in the SiO2 matrix, or in the 1-2 nm range in the Si3N4 matrix, as measured by transmission electron microscopy. Thus, Si3N4 matrix hosts Ge QDs at higher density and more closely spaced than SiO2 matrix. Raman spectroscopy revealed a higher threshold for amorphous-to-crystalline transition for Ge QDs embedded in Si3N4 matrix in comparison with those in the SiO2 host. Light absorption by Ge QDs is shown to be more effective in Si3N4 matrix, due to the optical bandgap (0.9-1.6 eV) being lower than in SiO2 matrix (1.2-2.2 eV). Significant photoresponse with a large measured internal quantum efficiency has been observed for Ge QDs in Si3N4 matrix when they are used as a sensitive layer in a photodetector device. These data will be presented and discussed, opening new routes for application of Ge QDs in light harvesting devices.

  15. A super junction SiGe low-loss fast switching power diode

    Institute of Scientific and Technical Information of China (English)

    Ma Li; Gao Yong

    2009-01-01

    This paper proposes a novel super junction (S J) SiGe switching power diode which has a columnar structure of alternating p-and n- doped pillar substituting conventional n- base region and has far thinner strained SiGe p+layer to overcome the drawbacks of existing Si switching power diode. The SJ SiCe diode can achieve low specific on-resistance, high breakdown voltages and fast switching speed. The results indicate that the forward voltage drop of SJ SiGe diode is much lower than that of conventional Si power diode when the operating current densities do not exceed 1000 A/cm2which is very good for getting lower operating loss. The forward voltage drop of the Si diode is 0.66 V whereas that of the SJ SiGe diode is only 0.52 V at operating current density of 10 A/cm2The breakdown voltages are 203 V for the former and 235 V for the latter. Compared with the conventional Si power diode, the reverse recovery time of SJ SiGe diode with 20 per cent Ge content is shortened by above a half and the peak reverse current is reduced by over 15%. The SJ SiGe diode can remarkably improve the characteristics of power diode by combining the merits of both SJ structure and SiGe material.

  16. Properties of three-dimensional structures prepared by Ge dewetting from Si(111) at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Shklyaev, Alexander, E-mail: shklyaev@isp.nsc.ru [A. V. Rzhanov Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Bolotov, Leonid; Poborchii, Vladimir; Tada, Tetsuya [National Institute of Advanced Industrial Science and Technology, Higashi 1-1-1, Tsukuba, Ibaraki 305-8562 (Japan)

    2015-05-28

    The formation of three-dimensional (3D) structures during Ge deposition on Si(111) at about 800 °C is studied with scanning tunneling, Kelvin probe and electron microscopies, and scanning tunneling and Raman spectroscopies. The observed surface morphology is formed by dewetting of Ge from Si(111), since it occurs mainly by means of minimization of surface and interfacial energies. The dewetting proceeds through massive Si eroding around growing 3D structures, providing them to be composed of SiGe with about a 30% Ge content, and leads to the significant reduction of the SiGe/Si interface area. It is found that the SiGe top component of 3D structures forms sharp interfaces with the underlying Si. The minimization of interfacial and strain energies occurs on the way that the 3D structures appear to get the dendrite-like shape. The Ge distribution in the 3D SiGe structures is inhomogeneous in the lateral dimension with a higher Ge concentration in their central areas and Ge segregation on their surface.

  17. Transport Properties of Si and Ge Liquid Semiconductor Metals

    Institute of Scientific and Technical Information of China (English)

    Aditya M. Vora

    2009-01-01

    In the present article, we study the electrical resistivity p, the thermoelectric power (TEP) α, thermal conductivity σ, Knight-ShiFts and temperature coefficient of the Knight-Shifts of the liquid Si and Ge using the well known model potential for the first time. The structure factor used in the present work is derived From the Percus-Yevick (PY) theory. Various local field correction Functions are used to study the screening influence. The present results of resistivity are found in qualitative agreement with available experimental and theoretical whenever exists.

  18. Degradation of SiGe devices by proton irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ohyama, Hidenori; Hayama, Kiyoteru [Kumamoto National Coll. of Technology, Nishigoshi (Japan); Vanhellemont, J.; Takami, Yasukiyo; Sunaga, Hiromi; Nashiyama, Isamu; Uwatoko, Yoshiya; Poortmans, J.; Caymax, M.

    1997-03-01

    The degradation and recovery behavior of strained Si{sub 1-x}Ge{sub x} diodes and heterojunction bipolar transistors (HBTs) by irradiated by protons are studied. The degradation of device performance and the generation of lattice defects are reported as a function of fluence and germanium content and also compared extensively with previous results obtained on electron and neutron irradiated devices. In order to study the recovery behavior of the irradiated devices, isochronal annealing is performed. The radiation source dependence of the degradation is discussed taking into account the number of knock-on atoms and the nonionizing energy loss (NIEL). (author)

  19. Diamond turning of Si and Ge single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Blake, P.; Scattergood, R.O.

    1988-12-01

    Single-point diamond turning studies have been completed on Si and Ge crystals. A new process model was developed for diamond turning which is based on a critical depth of cut for plastic flow-to-brittle fracture transitions. This concept, when combined with the actual machining geometry for single-point turning, predicts that {open_quotes}ductile{close_quotes} machining is a combined action of plasticity and fracture. Interrupted cutting experiments also provide a meant to directly measure the critical depth parameter for given machining conditions.

  20. A 122 GHz SiGe active subharmonic mixer

    OpenAIRE

    2005-01-01

    A 122 GHz subharmonic mixer for a radar-based sensor has been realized.It is fabricated in SiGe: C-HBT technology with a transit frequency of about 200 GHz. The conversion gain of the mixer is 23 dB at aLO-frequency of 60GHz with +3 dBm of power and a RF-input of 122.5GHz.The measured SSB noise figure at 122.5GHz is 12 dB.

  1. Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

    Science.gov (United States)

    Knapp, T. J.; Mohr, R. T.; Li, Yize Stephanie; Thorgrimsson, Brandur; Foote, Ryan H.; Wu, Xian; Ward, Daniel R.; Savage, D. E.; Lagally, M. G.; Friesen, Mark; Coppersmith, S. N.; Eriksson, M. A.

    2016-04-01

    We report the fabrication and characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. In the past, all gate-defined quantum dots in Si/SiGe heterostructures were formed on top of strain-graded virtual substrates. The strain grading process necessarily introduces misfit dislocations into a heterostructure, and these defects introduce lateral strain inhomogeneities, mosaic tilt, and threading dislocations. The use of a SiGe nanomembrane as the virtual substrate enables the strain relaxation to be entirely elastic, eliminating the need for misfit dislocations. However, in this approach the formation of the heterostructure is more complicated, involving two separate epitaxial growth procedures separated by a wet-transfer process that results in a buried non-epitaxial interface 625 nm from the quantum dot. We demonstrate that in spite of this buried interface in close proximity to the device, a double quantum dot can be formed that is controllable enough to enable tuning of the inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of an applied magnetic field.

  2. Growth Mechanism and Surface Structure of Ge Nanocrystals Prepared by Thermal Annealing of Cosputtered GeSiO Ternary Precursor

    Directory of Open Access Journals (Sweden)

    Bo Zhang

    2014-01-01

    Full Text Available Ge nanocrystals (Ge-ncs embedded in a SiO2 superlattice structure were prepared by magnetron cosputtering and postdeposition annealing. The formation of spherical nanocrystals was confirmed by transmission electron microscopy and their growth process was studied by a combination of spectroscopic techniques. The crystallinity volume fraction of Ge component was found to increase with crystallite size, but its overall low values indicated a coexistence of crystalline and noncrystalline phases. A reduction of Ge-O species was observed in the superlattice during thermal annealing, accompanied by a transition from oxygen-deficient silicon oxide to silicon dioxide. A growth mechanism involving phase separation of Ge suboxides (GeOx was then proposed to explain these findings and supplement the existing growth models for Ge-ncs in SiO2 films. Further analysis of the bonding structure of Ge atoms suggested that Ge-ncs are likely to have a core-shell structure with an amorphous-like surface layer, which is composed of GeSiO ternary complex. The surface layer thickness was extracted to be a few angstroms and equivalent to several atomic layer thicknesses.

  3. Physical studies of strained Si/SiGe heterostructures. From virtual substrates to nanodevices

    Energy Technology Data Exchange (ETDEWEB)

    Minamisawa, Renato Amaral

    2011-10-21

    During the past two decades, the decrease in intrinsic delay of MOSFETs has been driven by the scaling of the device dimensions. The performance improvement has relied mostly in the increase of source velocity with gate scaling, while the transport properties of the channel have remained constant, i.e., those of conventional Si. Starting at the 90 nm node, uniaxial strain has been introduced in the transistor channel in order to further increase the source velocity. Beyond the 32 nm node, novel channel materials, with superior carrier velocities, and novel device architectures are required in order to continue the performance enhancement of MOSFETs while preserving the electrostatic control. In this Thesis, different physical aspects of strained Si and SiGe materials are investigated as a mean to increase carrier velocity in MOSFET channels. Novel approaches for the fabrication of strained Si based on ion implantation and anneal induced relaxation of virtual substrates are developed. The strain relaxation of SiGe layers is improved using a buried thin Si:C layer in the Si(100) substrate. Further, a Si{sup +} ion implantation and annealing method is investigated for relaxing virtual substrates using lower implantation dose. Finally, the uniaxial relaxation of {l_brace}110{r_brace} surface oriented substrates is demonstrated using a He ion implantation and anneal technique. Apart of channel material studies, the fundamental and technological challenges involved in the integration of strained Si and SiGe into MOSFETs are assessed. The impact of source and drain formation on the elastic strain and electrical properties of strained Si layers and nanowires is examined. Also, the formation of ultra-shallow junction in strained Si/strained Si{sub 0.5}Ge{sub 0.5}/SSOI heterostructures is investigated using different types of ion implanted specie and annealing. The results show that BF{sup +}{sub 2} implantation and low temperature annealing are suitable approaches for

  4. Structural properties of tensily strained Si layers grown on SiGe(100), (110), and (111) virtual substrates

    Science.gov (United States)

    Destefanis, V.; Rouchon, D.; Hartmann, J. M.; Papon, A. M.; Baud, L.; Crisci, A.; Mermoux, M.

    2009-08-01

    We have studied the structural properties of tensily strained Si (t-Si) layers grown by reduced pressure-chemical vapor deposition on top of SiGe(100), (110), and (111) virtual substrates (VSs). Chemical mechanical planarization has been used beforehand to eliminate the as-grown surface crosshatch on all orientations and reduce by 10 up to 100 times the surface roughness. A definite surface roughening has occurred after the epitaxy of t-Si on (110) and (111). For the lowest Ge contents investigated, top Si(100) and (110) layers are locally "defect-free" whereas numerous {111} stacking faults are present in the t-Si(111) layers. For higher Ge content SiGe VS, a degradation of the crystallographic quality of (110) and (111) t-Si layers has been evidenced, with the presence of dislocations, stacking faults, and twins. Quantification of the strain level in the t-Si layers has been carried out using visible and near-UV Raman spectroscopy. The Ge contents in the VS determined by Raman spectroscopy were very close to the ones previously obtained by secondary ion mass spectrometry or x-ray diffraction. Stress values obtained for t-Si(100) layers were whatever the Ge content similar to those expected. Stress values corresponding to pseudomorphic t-Si growths have been obtained on (110) and (111) SiGe VSs, for Ge contents up to 35% and 25%, respectively. The stress values obtained on (110) surfaces for such Ge contents were high, with a noticeable anisotropy along the [001] and [1-10] directions. Degradations of the (110) and (111) Raman profiles likely coming from twin-assisted strain relaxation have been noticed for t-Si layers on SiGe VS with Ge contents higher than 35% and 25%, respectively. UV and visible Raman mapping of the growth plane strain fluctuations has finally been carried out. Original surface arrays have been highlighted for each surface orientation. Such strain fields are related to the plastic relaxation of strain in the SiGe graded layer underneath

  5. Undoped Heterostructure Materials for SiGe Quantum Devices

    Science.gov (United States)

    Ross, R. S.; Borselli, M. G.; Huang, B.; Holabird, K. S.; Hazard, T. M.; Kiselev, A. A.; Deelman, P. W.; Alvarado-Rodriguez, I.; Schmitz, A. E.; Sokolich, M.; Hunter, A. T.; Gyure, M. F.

    2011-03-01

    Quantum well heterostructures, widely used for the fabrication of quantum dots and related devices, typically make use of modulation doping. Removal of the dopants, by use of globally ``field-gated'' and/or back-gated heterostructure designs, eliminates the dominant sources of scattering, charge noise and instability in devices intended for low-temperature operation. In this talk we present recent progress in designing and fabricating undoped quantum well heterostructures in sSi/SiGe. A combination of simulation based modeling and experimental work has enabled us to successfully engineer materials for stable and quiet quantum dot operation. Specific topics to be presented include the important role of substrate and buffer layer background doping, concurrent MOS accumulation, leakage to front and back gates via barrier tunneling, and the expected range of electric fields that determine valley mixing in quantum dots. Sponsored by United States Department of Defense. Approved for Public Release, Distribution Unlimited.

  6. Double Sided Si(Ge)/Sapphire/III-Nitride Hybrid Structure

    Science.gov (United States)

    Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor)

    2016-01-01

    One aspect of the present invention is a double sided hybrid crystal structure including a trigonal Sapphire wafer containing a (0001) C-plane and having front and rear sides. The Sapphire wafer is substantially transparent to light in the visible and infrared spectra, and also provides insulation with respect to electromagnetic radio frequency noise. A layer of crystalline Si material having a cubic diamond structure aligned with the cubic direction on the (0001) C-plane and strained as rhombohedron to thereby enable continuous integration of a selected (SiGe) device onto the rear side of the Sapphire wafer. The double sided hybrid crystal structure further includes an integrated III-Nitride crystalline layer on the front side of the Sapphire wafer that enables continuous integration of a selected III-Nitride device on the front side of the Sapphire wafer.

  7. High Quality GaAs Growth by MBE on Si Using GeSi Buffers and Prospects for Space Photovoltaics

    Science.gov (United States)

    Carlin, J. A.; Ringel, S. A.; Fitzgerald, E. A.; Bulsara, M.

    2005-01-01

    III-V solar cells on Si substrates are of interest for space photovoltaics since this would combine high performance space cells with a strong, lightweight and inexpensive substrate. However, the primary obstacles blocking III-V/Si cells from achieving high performance to date have been fundamental materials incompatabilities, namely the 4% lattice mismatch between GaAs and Si, and the large mismatch in thermal expansion coefficient. In this paper, we report on the molecular beam epitaxial (MBE) growth and properties of GaAs layers and single junction GaAs cells on Si wafers which utilize compositionally graded GeSi Intermediate buffers grown by ultra-high vacuum chemical vapor deposition (UHVCVD) to mitigate the large lattice mismatch between GaAs and Si. Ga As cell structures were found to incorporate a threading dislocation density of 0.9-1.5 x 10 (exp 6) per square centimeter, identical to the underlying relaxed Ge cap of the graded buffer, via a combination of transmission electron microscopy, electron beam induced current, and etch pit density measurements. AlGaAs/GaAs double heterostructures wre grown on the GeSi/Si substrates for time-resolved photoluminescence measurements, which revealed a bulk GaAs minority carrier lifetime in excess of 10 ns, the highest lifetime ever reported for GaAs on Si. A series of growth were performed to ass3ss the impact of a GaAs buffer to a thickness of only 0.1 micrometer. Secondary ion mass spectroscopy studies revealed that there is negligible cross diffusion of Ga, As and Ge at he III-V/Ge interface, identical to our earlier findings for GaAs grown on Ge wafers using MBE. This indicates that there is no need for a buffer to "bury" regions of high autodopjing,a nd that either pn or np configuration cells are easily accomodated by these substrates. Preliminary diodes and single junction Al Ga As heteroface cells were grown and fabricated on the Ge/GeSi/Si substrates for the first time. Diodes fabricated on GaAs, Ge and Ge/GeSi/Si

  8. Surfactant-mediated epitaxy of thin germanium films on SiGe(001) virtual substrates

    Science.gov (United States)

    Schmidt, J.; Tetzlaff, D.; Bugiel, E.; Wietler, T. F.

    2017-01-01

    We report on the impact of a surfactant on the growth mode and strain relaxation of thin Ge films on Si0.21Ge0.79 virtual substrates grown by surfactant mediated epitaxy on Si(001) wafers. Ge epitaxy without surfactant results in island formation after deposition of only 5 nm Ge. A certain part of the strain in the Ge islands is relaxed via interfacial misfit dislocations, which are located within the core part of the islands. We discuss the possibilities for the occurrence of three-dimensional growth at low Ge layer thickness. The use of Sb as a surfactant suppresses three-dimensional islanding and enables the growth of smooth pseudomorphically strained Ge films on Si0.21Ge0.79(001) virtual substrates up to a thickness of 10 nm. At thicknesses higher than 20 nm, the films relax via the formation of a misfit dislocation network at the Ge/ Si1-xGex interface. The surface roughness of up to 30 nm thick layers is below 1.6 nm. Our experimental results corroborate the calculated thickness for plastic relaxation of Ge on Si1-xGex. The effect of the surfactant on the growth of the virtual substrate and on the subsequent growth of Ge on Si0.21Ge0.79 is discussed.

  9. Epitaxy relationships between Ge-islands and SiC(0 0 0 1)

    Energy Technology Data Exchange (ETDEWEB)

    Ait-Mansour, K. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France)]. E-mail: k.ait-mansour@uha.fr; Dentel, D. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France); Kubler, L. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France); Diani, M. [Departement de Physique, Faculte des Sciences et Techniques, LSGM, BP 416, Tanger, Maroc (Morocco); Bischoff, J.L. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France); Bolmont, D. [Faculte des Sciences, LPSE, UMR CNRS 7014, 4, rue des Freres Lumiere, 68093 Mulhouse, Cedex (France)

    2005-03-15

    Reflection high-energy electron diffraction (RHEED) has been used to determine epitaxy relationships and in-plane orientations between Ge and SiC(0 0 0 1). Three monolayers of Ge have been deposited at 500 deg. C on a graphitized SiC (6{radical}3 x 6{radical}3)R30 deg. reconstructed surface, this surface supporting epitaxial Ge island growth in a Volmer-Weber mode. Nucleation of relaxed Ge-islands gives rise to transmission electron diffraction patterns allowing to deduce that pure Ge grows according to only one epitaxy relationship Ge{l_brace}1 1 1{r_brace}//SiC(0 0 0 1). These {l_brace}1 1 1{r_brace}-Ge-islands have two in-plane orientations, a preferential one, Ge<-1-12>//SiC<1-100> and a minority one, Ge<-1-12>//SiC<10-10>, deduced one from the other by a 30 deg. rotation around the <1 1 1>-Ge (or [0 0 0 1]-SiC) growth axis. Due to the three-fold symmetry of the {l_brace}1 1 1{r_brace}-Ge plane, each in-plane orientation is degenerated into two twin orientations, differing by a 180 deg. angle around Ge<111>.

  10. Production of three-dimensional quantum dot lattice of Ge/Si core-shell quantum dots and Si/Ge layers in an alumina glass matrix

    Science.gov (United States)

    Buljan, M.; Radić, N.; Sancho-Paramon, J.; Janicki, V.; Grenzer, J.; Bogdanović-Radović, I.; Siketić, Z.; Ivanda, M.; Utrobičić, A.; Hübner, R.; Weidauer, R.; Valeš, V.; Endres, J.; Car, T.; Jerčinović, M.; Roško, J.; Bernstorff, S.; Holy, V.

    2015-02-01

    We report on the formation of Ge/Si quantum dots with core/shell structure that are arranged in a three-dimensional body centered tetragonal quantum dot lattice in an amorphous alumina matrix. The material is prepared by magnetron sputtering deposition of Al2O3/Ge/Si multilayer. The inversion of Ge and Si in the deposition sequence results in the formation of thin Si/Ge layers instead of the dots. Both materials show an atomically sharp interface between the Ge and Si parts of the dots and layers. They have an amorphous internal structure that can be crystallized by an annealing treatment. The light absorption properties of these complex materials are significantly different compared to films that form quantum dot lattices of the pure Ge, Si or a solid solution of GeSi. They show a strong narrow absorption peak that characterizes a type II confinement in accordance with theoretical predictions. The prepared materials are promising for application in quantum dot solar cells.

  11. Electrical characterization of SiGeSn grown on Ge substrate using ultra high vacuum chemical vapor deposition

    Science.gov (United States)

    Ahoujja, Mo; Kang, S.; Hamilton, M.; Yeo, Y. K.; Kouvetakis, J.; Menendez, J.

    2012-02-01

    There has been recently considerable interest in growing SiyGe1-x-ySnx alloys for the fabrication of photonic devices that could be integrated with Si technologies. We report temperature dependent Hall (TDH) measurements of the hole concentration and mobility from high quality p-type doped Si0.08Ge0.90Sn0.02 layers grown on p-type doped Ge substrates using ultra high vacuum chemical vapor deposition. The TDH measurements show the hole sheet density remains constant at low temperatures before slightly decreasing and dipping at ˜ 125 K. It then exponentially increases with temperature due to the activation of shallow acceptors. At temperatures above ˜ 450 K, the hole sheet density increases sharply indicating the onset of intrinsic conduction in the SiGeSn and/or Ge layers. To extract the electrical properties of the SiGeSn layer alone, a parametric fit using a multi layer conducting model is applied to the measured hole concentration and mobility data. The analysis yields boron and gallium doping concentrations of 3x10^17 cm-3 and 1x10^18 cm-3 with activation energies of 10 meV and 11 meV for the SiGeSn layer and Ge substrate, respectively. Furthermore, a temperature independent hole sheet concentration of ˜5x10^15 cm-2 with a mobility of ˜250 cm^2/Vs, which is believed to be due to an interfacial layer between the SiGeSn layer and the Ge substrate, is also determined.

  12. Electric properties of Ge quantum dot embedded in Si matrix

    Institute of Scientific and Technical Information of China (English)

    MA Xi-ying; SHI Wei-lin

    2005-01-01

    The electric characteristics of Ge quantum dot grown by molecular beam epitaxy in Si matrix were investigated by admittance spectroscopy and deep level transient spectroscopy. The admittance spectroscopy measurements show that the activation energy of 0.341 eV can be considered as the emitting energy of hole from the ground state of the quantum dot. And the capacitance variation with temperature of the sample shows a platform at various frequencies with reverse bias 0.5 V, which indicates that the boundary of space charge region is located at the quantum dot layer where the large confined hole concentration blocks the further extension of space charge region. When the temperature increases from 120 K to 200 K, the holes in the dot emit out completely. The position of the platform shifting with the increase of the applied frequency shows the frequency effects of the charges in the quantum dot. The deep level transient spectroscopy results show that the charge concentration in the Ge quantum dot is a function of the pulse duration and the reverse bias voltage, the activation energy and capture cross-section of hole decrease with the increase of pulse duration due to the Coulomb charging effect. The valence-band offsets of hole in Ge dot obtained by admittance spectroscopy and deep level transient spectroscopy are 0.341 and 0.338 eV, respectively.

  13. SiGe crystal growth aboard the international space station

    Science.gov (United States)

    Kinoshita, K.; Arai, Y.; Tsukada, T.; Inatomi, Y.; Miyata, H.; Tanaka, R.

    2015-05-01

    A silicon germanium mixed crystal Si1-xGex (x~0.5) 10 mm in diameter and 9.2 mm in length was grown by the traveling liquidus-zone (TLZ) method in microgravity by suppressing convection in a melt. Ge concentration of 49.8±2.5 at% has been established for the whole of the grown crystal. Compared with the former space experiment, concentration variation in the axial direction increased from ±1.5 at% to ±2.5 at% although average Ge concentration reached to nearly 50 at%. Excellent radial Ge compositional uniformity 52±0.5 at% was established in the region of 7-9 mm growth length, where axial compositional uniformity was also excellent. The single crystalline region is about 5 mm in length. The interface shape change from convex to concave is implied from both experimental results and numerical analysis. The possible cause of increase in concentration variation and interface shape change and its relation to the two-dimensional growth model are discussed.

  14. Growth kinetic and doping of Si and SiGe epi layers on fullsheet substrates

    Energy Technology Data Exchange (ETDEWEB)

    Talbot, Alexandre [STMicroelectronicsonic, 850 rue jean Monnet, BP 38921 Crolles (France)]. E-mail: alexandre.talbot@st.com; Avenier, Gregory [STMicroelectronicsonic, 850 rue jean Monnet, BP 38921 Crolles (France); Vincent, Gilbert [UJF, LTM, LETI-DTS, CEA Grenoble, 17 Avenue des Martyrs, 38054 Grenoble, Cedex 9 (France); Dutartre, Didier [STMicroelectronicsonic, 850 rue jean Monnet, BP 38921 Crolles (France)

    2004-12-15

    As the critical size of MOSFET becomes smaller and smaller and complexity of architectures increases, selective and non-selective depositions of in situ doped film become extremely attractive for the realisation of new devices architectures like, elevated sources/drains in CMOS or extrinsic bases in bipolar. Epitaxial layers were grown in a 200 mm industrial single wafer reactor. Firstly, we investigate the boron incorporation in Si/SiGe non-selective epitaxy based on SiH{sub 4}/GeH{sub 4}/B{sub 2}H{sub 6}/H{sub 2} chemistry at low temperature (550-750 deg. C). The influence of temperature and germanium content on the boron incorporation is presented. Sheet conductivity deduced from four probes measurements varied from 1.8 x 10{sup 4} to 1.9 x 10{sup 5} S m{sup -1} as deposited. We demonstrate that both the boron incorporation and the film conductivity are improved in SiGe compared to Si. In addition, combining the dose of substitutional boron atoms, deduced from the X-ray diffraction shift, with the resistivity results, we could infer a significant enhancement of the hole mobility in SiGe compared to Si (at least for moderate doping levels around 1 x 10{sup 20} h/cm{sup 3}). In a second part, the high boron-doping of selective Si epitaxy based on SiH{sub 2}Cl{sub 2}/B{sub 2}H{sub 6}/HCl/H{sub 2} chemistry at reduced pressure (<20 Torr) and at low temperature (700-850 deg. C) is examined. Boron incorporation is observed to decrease with increasing HCl flow and the electrical doping level to increase with temperature. We also report a strong increase of the growth rate with the dopant flow (six times higher for B{sub 2}H{sub 6}/DCS = 0.01) that will be discussed. Epitaxies that are fully selective against Si{sub 3}N{sub 4} have been demonstrated with conductivity as high as 7.8 x 10{sup 4} S m{sup -1}.

  15. Large area and depth-profiling dislocation imaging and strain analysis in Si/SiGe/Si heterostructures.

    Science.gov (United States)

    Chen, Xin; Zuo, Daniel; Kim, Seongwon; Mabon, James; Sardela, Mauro; Wen, Jianguo; Zuo, Jian-Min

    2014-10-01

    We demonstrate the combined use of large area depth-profiling dislocation imaging and quantitative composition and strain measurement for a strained Si/SiGe/Si sample based on nondestructive techniques of electron beam-induced current (EBIC) and X-ray diffraction reciprocal space mapping (XRD RSM). Depth and improved spatial resolution is achieved for dislocation imaging in EBIC by using different electron beam energies at a low temperature of ~7 K. Images recorded clearly show dislocations distributed in three regions of the sample: deep dislocation networks concentrated in the "strained" SiGe region, shallow misfit dislocations at the top Si/SiGe interface, and threading dislocations connecting the two regions. Dislocation densities at the top of the sample can be measured directly from the EBIC results. XRD RSM reveals separated peaks, allowing a quantitative measurement of composition and strain corresponding to different layers of different composition ratios. High-resolution scanning transmission electron microscopy cross-section analysis clearly shows the individual composition layers and the dislocation lines in the layers, which supports the EBIC and XRD RSM results.

  16. Lattice Thermal Conductivity of the Binary and Ternary Group-IV Alloys Si-Sn, Ge-Sn, and Si-Ge-Sn

    Science.gov (United States)

    Khatami, S. N.; Aksamija, Z.

    2016-07-01

    Efficient thermoelectric (TE) energy conversion requires materials with low thermal conductivity and good electronic properties. Si-Ge alloys, and their nanostructures such as thin films and nanowires, have been extensively studied for TE applications; other group-IV alloys, including those containing Sn, have not been given as much attention as TEs, despite their increasing applications in other areas including optoelectronics. We study the lattice thermal conductivity of binary (Si-Sn and Ge-Sn) and ternary (Si-Ge-Sn) alloys and their thin films in the Boltzmann transport formalisms, including a full phonon dispersion and momentum-dependent boundary-roughness scattering. We show that Si-Sn alloys have the lowest conductivity (3 W /mK ) of all the bulk alloys, more than 2 times lower than Si-Ge, attributed to the larger difference in mass between the two constituents. In addition, we demonstrate that thin films offer an additional reduction in thermal conductivity, reaching around 1 W /mK in 20-nm-thick Si-Sn, Ge-Sn, and ternary Si-Ge-Sn films, which is near the conductivity of amorphous SiO2 . We conclude that group-IV alloys containing Sn have the potential for high-efficiency TE energy conversion.

  17. Silver(i)-promoted insertion into X-H (X = Si, Sn, and Ge) bonds with N-nosylhydrazones.

    Science.gov (United States)

    Liu, Zhaohong; Li, Qiangqiang; Yang, Yang; Bi, Xihe

    2017-02-21

    Silver(i)-promoted carbene insertion into X-H (X = Si, Sn, and Ge) bonds has been realized by using unstable diazo compounds, which are generated in situ from N-nosylhydrazones as carbene precursors. The reaction tolerates a wide range of functional groups and delivers a number of valuable silicon-containing compounds in very high yields (up to 96%). Moreover, organostannanes and organogermanes were as well effectively obtained in very good yields under optimal conditions.

  18. Magnetocaloric Effect in MnCo_(1-x)Al_xGe Compounds

    Institute of Scientific and Technical Information of China (English)

    Weiguang Zhang; O. Tegus; Yongli Wu; Yirgeltu; Huanying Yan; Song Lin

    2009-01-01

    The effects of substitution of Al for Co on magnetic and magnetocaloric properties of MnCo_(1-x)Al_xGe (x=0.00, 0.03, 0.05, 0.08, 0.10, 0.13, 0.15, and 0.20) compounds have been investigated by X-ray diffraction (XRD) and magnetization measurements. XRD exhibits that MnCo_(1-x)Al_xGe compounds crystallize in the orthorhombic TiNiSi-type structure for x0.03. Magnetic measurements show that the Curie temperature can be tuned between 286 and 347 K by changing the Co/Al ratio. The maximum magnetic entropy change determined from the isothermal magnetization measurement by Maxwell relation reaches 1.52 J/(kgK) for x=0.08 in a field change from 0 to 1.5 T around 310 K.

  19. Density Functional Theory Study on Mechanism of Forming Spiro-Ge-heterocyclic Ring Compound from Me2Ge=Ge: and Acetaldehyde

    Institute of Scientific and Technical Information of China (English)

    Xiu-hui Lu; Yong-qing Li; Wei-jie Bao; Dong-ting Liu

    2013-01-01

    The H2Ge=Ge:,as well as and its derivatives (X2Ge=Ge:,X=H,Me,F,CI,Br,Ph,Ar,...)is a kind of new species.Its cycloaddition reactions is a new area for the study of germylene chemistry.The mechanism of the cycloaddition reaction between singlet Me2Ge=Ge:and acetaldehyde was investigated with the B3LYP/6-31G* method in this work.From the potential energy profile,it could be predicted that the reaction has one dominant reaction pathway.The reaction rule is that the two reactants firstly form a four-membered Ge-heterocyclic ring germylene through the [2+2] cycloaddition reaction.Because of the 4p unoccupied orbital of Ge:atom in the four-membered Ge-heterocyclic ring germylene and the π orbital of acetaldehyde forning a π-p donor-acceptor bond,the four-membered Ge-heterocyclic ring germylene further combines with acetaldehyde to form an intermediate.Because the Ge atom in intermediate happens sp3 hybridization after transition state,then,intermediate isomerizes to a spiro-Ge-heterocyclic ring compound via a transition state.The research result indicates the laws of cycloaddition reaction between Me2Ge=Ge:and acetaldehyde,and lays the theory foundation of the cycloaddition reaction between H2Ge=Ge:and its derivatives (X2Ge=Ge:,X=H,Me,F,Cl,Br,Ph,Ar) and asymmetric π-bonded compounds,which are significant for the synthesis of small-ring and spiro-Ge-heterocyclic ring compounds.

  20. Photoluminescence study of high density Si quantum dots with Ge core

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, K., E-mail: kondou.keigo@b.mbox.nagoya-u.ac.jp; Makihara, K.; Ikeda, M.; Miyazaki, S. [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2016-01-21

    Si quantum dots (Si-QDs) with Ge core were self-assembled on thermally grown SiO{sub 2} from alternate thermal decomposition of pure SiH{sub 4} and GeH{sub 4} diluted with He. When the sample was excited by the 979 nm line of a semiconductor laser, fairly broad photoluminescence (PL) spectra in the region of 0.6–0.8 eV were observed at room temperature. The observed PL spectra suggested that radiative recombination of photo-generated carriers through quantized states of Ge core is the dominant pathway for the emission from the dots, reflecting the type II energy band discontinuity between the Si clad and Ge core. We also found that P-δ doping to Ge core plays an important role in recombination through the quantized states in the valence band of Ge core and P donor levels.

  1. Characterization of Si sub 1 sub - sub x Ge sub x thin films prepared by sputtering

    CERN Document Server

    Noguchi, T

    2000-01-01

    By bombarding solid targets, we deposited Si sub 1 sub - sub x Ge sub x thin films by sputtering without using inflammable CVD (chemical vapor deposition) gases. After the B sup + -implanted Si sub 1 sub - sub x Ge sub x films were thermally annealed, they were characterized. As the content of Ge increased, the refractive index increased and the band edge narrowed. The higher the annealing temperature, the lower the resistivity. For Si sub 1 sub - sub x Ge sub x films with a high Ge content (X approx 0.5), the flat-band voltage of the gate deduced from C-V curve was adjusted to the middle point between p sup + and n sup + polySi gates. Boron-doped SiGe films are promising gate materials for MOS (metal oxide semiconductor) and SOI (silicon on insulator) transistors driven at low driving voltage.

  2. Structure and physical properties of RE{sub 2}AgGe{sub 3} (RE=Ce, Pr, Nd) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Sumanta; Mumbaraddi, Dundappa; Halappa, Pramod; Kalsi, Deepti [New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064 (India); Rayaprol, Sudhindra [UGC-DAE Consortium for Scientific Research, Mumbai Centre, R-5 Shed, BARC Campus, Mumbai 400085 (India); Peter, Sebastian C., E-mail: sebastiancp@jncasr.ac.in [New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064 (India)

    2015-09-15

    We have synthesized the compounds RE{sub 2}AgGe{sub 3} (RE =Ce, Pr, Nd) by arc melting. The crystal structure obtained from single crystal and powder X-ray diffraction suggests that these compounds crystallize in the α-ThSi{sub 2} structure type. The magnetic susceptibility data of Ce{sub 2}AgGe{sub 3} follows Curie–Weiss (CW) law above 25 K without any magnetic ordering down to 2 K. The effective magnetic moment (μ{sub eff}) was calculated as 2.53 μ{sub B}/Ce and negative Curie paramagnetic temperature (θ{sub p})=−2.4 K hint weak antiferromagnetic coupling among the adjacent spins. Pr{sub 2}AgGe{sub 3} shows a complex magnetic behavior wherein the magnetic susceptibility at field cooled and zero field cooled modes bifurcates at 11.5 K with the latter undergoing a cusp like maxima, probably due to weak ferromagnetic interaction. The θ{sub p} and μ{sub eff} obtained are 4 K and 4.33 μ{sub B}/Pr, respectively. Nd{sub 2}AgGe{sub 3} undergoes multiple magnetic transitions. Temperature dependent resistivity data reveals that three compounds are metallic in nature. - Graphical abstract: The compounds Ce{sub 2}AgGe{sub 3}, Pr{sub 2}AgGe{sub 3} and Nd{sub 2}AgGe{sub 3} have been synthesized by arc melting. X-ray diffraction suggests tetragonal α-ThSi{sub 2} type structure and diverse magnetic properties exhibited in the magnetic measurements. - Highlights: • Two new compounds Ce{sub 2}AgGe{sub 3}, Nd{sub 2}AgGe{sub 3} and known Pr{sub 2}AgGe{sub 3} synthesized by arc melting. • Crystal structure of the compounds derived from X-ray diffraction. • Ce{sub 2}AgGe{sub 3} and Pr{sub 2}AgGe{sub 3} exhibit antiferromagnetic ordering. • Nd{sub 2}AgGe{sub 3} shows multiple magnetic transition with ferrimagnetic like behavior.

  3. Si基Ge/SiGeⅠ型量子阱结构的理论设计和实验研究%Design and experiment of Si-based Ge/SiGe type-Ⅰ quantum well structure

    Institute of Scientific and Technical Information of China (English)

    陈城钊; 陈阳华; 黄诗浩; 李成; 赖虹凯; 陈松岩

    2012-01-01

    Si-based Ge/SiGe type-Ⅰ quantum well is theoretically designed based on the energy band engineering theory.High-quality Ge/ SiGe multiple quantum wells were grown on Si-based germanium virtual substrates by ultra-high vacuum chemical vapor deposition.When the thickness of the Ge quantum well is reduced from 15 nm to 12 nm and 11 nm,the quantum confinement effect in the Ge/SiGe quantum wells can be directly demonstrated by room temperature photoluminescence(PL),which is in good agreement with the theoretical prediction.But when the thickness of the Ge quantum well is gradually reduced to 9 nm and 7 nm,the experimental result doesn′t obey the theoretical prediction.Further experiments reveal the reason that when the thickness of the Ge quantum well is reduced to some extent,the photoluminescence from the direct band transition of the Ge well will be restrained and it mainly originates from the Ge virtual substrate.%基于能带工程理论,设计了Si基Ge/SiGeⅠ型量子阱结构。采用超高真空化学气相淀积系统,制备出高质量的Si基Ge/SiGe多量子阱系列材料。当样品中Ge量子阱宽从15nm减少到12nm和11nm时,室温下荧光(PL)光谱观测到量子限制效应引起的直接带跃迁发光峰位的蓝移,峰位的实验值与理论值符合得很好;当Ge量子阱宽逐渐减小到9nm和7nm时,测试得到样品的PL谱峰位却与理论预期出现了较大的差值。进一步的实验表明,这主要是由于量子阱厚度小到一定程度时,量子阱的直接带发光受到抑制,其发光主要源于Ge虚拟衬底。

  4. Temperature spectra of conductance of Ge/Si p-i-n structures with Ge quantum dots

    Science.gov (United States)

    Izhnin, Ihor I.; Fitsych, Olena I.; Pishchagin, Anton A.; Kokhanenko, Andrei P.; Voitsekhovskii, Alexander V.; Dzyadukh, Stanislav M.; Nikiforov, Alexander I.

    2017-02-01

    This work presents results of investigation of Ge/Si p-i-n structures with Ge quantum dots in the i-region by the method of admittance spectroscopy. The structures contain multiple layers with Ge quantum dots separated by thin 5 nm layers of Si in the intrinsic region. Two peaks are observed on the temperature dependences of conductance of the investigated heterostructures. It is revealed that the second peak is broadened and corresponds to a system of closely lying energy levels.

  5. Hard-photon emission from 150-GeV electrons incident on Si and Ge single crystals near axial directions

    Energy Technology Data Exchange (ETDEWEB)

    Medenwaldt, R.; Moller, S.P.; Sorensen, A.H.; Tang-Petersen, S.; Uggerhoj, E. (Institute of Physics, University of Aarhus, DK-8000 Aarhus C, Denmark (DK)); Elsener, K. (European Organization for Nuclear Research (CERN), CH-1211 Geneva 23, Switzerland (CH)); Hage-Ali, M.; Siffert, P.; Stoquert, J. (Centre de Recherches Nucleaires, F-67037 Strasbourg CEDEX, France (FR)); Maier, K. (The Max-Planck Institut fuer Metallforschung, D-7000 Stuttgart 80, Federal Republic of Germany (DE))

    1989-12-25

    The emission of high-energy photons from 150-GeV electrons traversing single crystals near axial directions is studied experimentally for Ge and, for the first time, also for Si. Enhancements relative to random up to 2 orders of magnitude are observed. For incident angles much less than the critical channeling angle {psi}{sub 1} a pronounced peak appears in the photon spectra near {similar to}85% of the electron energy for both the Si and the Ge crystals. The peak disappears for incident angles larger than {similar to}0.3{psi}{sub 1}. The experimental findings are compared to theoretical results.

  6. Reverse current reduction of Ge photodiodes on Si without post-growth annealing Invited Paper

    Institute of Scientific and Technical Information of China (English)

    Sungbong Park; Shinya Takita; Yasuhiko; Ishikawa; Jiro Osaka; Kazumi Wada

    2009-01-01

    A new approach to reduce the reverse current of Ge pin photodiodes on Si is presented, in which an i-Si layer is inserted between Ge and top Si layers to reduce the electric field in the Ge layer. Without post- growth annealing, the reverse current density is reduced to ~10 mA/cm2 at -1 V, i.e., over one order of magnitude lower than that of the reference photodiode without i-Si layer. However, the responsivity of the photodiodes is not severely compromised. This lowered-reverse-current is explained by band-pinning at the i-Si/i-Ge interface. Barrier lowering mechanism induced by E-field is also discussed. The presented "non-thermal" approach to reduce reverse current should accelerate electronics-photonics convergence by using Ge on the Si complementary metal oxide semiconductor (CMOS) platform.

  7. Low electrical resistivity polycrystalline SiGe films obtained by vertical LPCVD for MOS devices

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira, Ricardo Cotrin [State University of Campinas (UNICAMP), Center for Semiconductor Components (CCS), School of Electrical and Computer Engineering - FEEC, Rua Joao Pandia Calogeras, 90 Caixa Postal 6061, CEP 13083-870 Campinas-SP (Brazil); Doi, Ioshiaki [State University of Campinas (UNICAMP), Center for Semiconductor Components (CCS), School of Electrical and Computer Engineering - FEEC, Rua Joao Pandia Calogeras, 90 Caixa Postal 6061, CEP 13083-870 Campinas-SP (Brazil)]. E-mail: doi@led.unicamp.br; Zakia, Maria Beny Pinto [State University of Campinas (UNICAMP), Center for Semiconductor Components (CCS), School of Electrical and Computer Engineering - FEEC, Rua Joao Pandia Calogeras, 90 Caixa Postal 6061, CEP 13083-870 Campinas-SP (Brazil); Diniz, Jose Alexandre [State University of Campinas (UNICAMP), Center for Semiconductor Components (CCS), School of Electrical and Computer Engineering - FEEC, Rua Joao Pandia Calogeras, 90 Caixa Postal 6061, CEP 13083-870 Campinas-SP (Brazil); Swart, Jacobus Willibrordus [State University of Campinas (UNICAMP), Center for Semiconductor Components (CCS), School of Electrical and Computer Engineering - FEEC, Rua Joao Pandia Calogeras, 90 Caixa Postal 6061, CEP 13083-870 Campinas-SP (Brazil)

    2005-12-05

    In this study, authors present some morphological and electrical characterization of polycrystalline SiGe thin films (poly-SiGe) deposited by vertical LPCVD using SiH{sub 4}, GeH{sub 4} and H{sub 2} mixture in different deposition parameters aiming for MOS gate electrodes. The obtained thin films are very uniform and smooth, with small grain size, feasible to deep submicrom fabrication. The SiGe samples presented resistivity values as low as 0.42 m{omega} cm, one order of magnitude lower than poly-Si reference samples. CV and IV measurements points this poly-SiGe as a suitable material for MOS gate electrodes.

  8. SiGeSn growth studies using reduced pressure chemical vapor deposition towards optoelectronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Wirths, S., E-mail: s.wirths@fz-juelich.de [Peter Grünberg Institute (PGI 9-IT) and JARA-FIT, Forschungszentrum Juelich, 52425 (Germany); Buca, D. [Peter Grünberg Institute (PGI 9-IT) and JARA-FIT, Forschungszentrum Juelich, 52425 (Germany); Ikonic, Z.; Harrison, P. [Institute of Microwaves and Photonics, School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Tiedemann, A.T.; Holländer, B.; Stoica, T.; Mussler, G. [Peter Grünberg Institute (PGI 9-IT) and JARA-FIT, Forschungszentrum Juelich, 52425 (Germany); Breuer, U. [Central Institute for Engineering, Electronics and Analytics (ZEA-3), Forschungszentrum Juelich, 52425 (Germany); Hartmann, J.M. [CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble (France); Grützmacher, D.; Mantl, S. [Peter Grünberg Institute (PGI 9-IT) and JARA-FIT, Forschungszentrum Juelich, 52425 (Germany)

    2014-04-30

    In this contribution, we propose a laser concept based on a double heterostructure consisting of tensile strained Ge as the active medium and SiGeSn ternaries as cladding layers. Electronic band-structure calculations were used to determine the Si and Sn concentrations yielding a type I heterostructure with appropriate band-offsets (50 meV) between strained Ge and SiGeSn. Reduced pressure chemical vapor deposition system was employed to study the laser structure growth. Detailed analyses regarding layer composition, crystal quality, surface morphology and elastic strain are presented. A strong temperature dependence of the Si and Sn incorporation has been obtained, ranging from 4 to 19 at.% Si and from 4 to 12 at.% Sn (growth temperatures between 350 °C and 475 °C). The high single crystalline quality and low surface roughness of 0.5–0.75 nm demonstrate that our layers are suitable for heterostructure laser fabrication. - Highlights: • Sn based group IV materials for photonics • Bandstructure calculations of SiGeSn/strained Ge double heterostructures. • Si and Sn concentrations in SiGeSn layers between 4 and 19 at.% and 4 and 11 at.%, respectively. • Growth of SiGeSn layers with high crystalline quality for optoelectronic applications.

  9. Efficient injection-type ballistic rectification in Si/SiGe cross junctions

    Science.gov (United States)

    Salloch, D.; Wieser, U.; Kunze, U.; Hackbarth, T.

    2010-09-01

    Tunable inertial-ballistic rectification is studied in a nanoscale injection-type Si/SiGe rectifier in the hot-electron regime. The rectifier consists of a cascade of two nanoscale cross junctions in series. Two pairs of opposing current injectors merge under 30∘ into a straight central voltage stem. The electron densities in the injectors and the stem can be adjusted separately by two local top-gates. The measurements reveal a substantial efficiency increase for a nearly depleted stem. The efficiency of ballistic rectifiers can be expressed by the transfer resistance RT (output voltage divided by input current), the best value we achieve is 800 Ω.

  10. Simulation of Domain Formation in p-Si/SiGe Quantum Cascade Structures

    Science.gov (United States)

    Ikonic, Z.; Harrison, P.; Kelsall, R. W.

    Domain formation in p-doped Si/SiGe quantum cascades is considered using a carrier scattering transport framework. The hole flow along the cascade is described via scattering between quantized states belonging to neighbouring periods, caused by phonons, alloy disorder, and carrier-carrier interactions. The generation of either periodic or of nonperiodic domains is studied in uniformly or modulationally doped cascades, and criteria for their appearance are found. The domains in modulationally doped cascades have a relatively smaller effect on the energy structure than in uniformly doped ones.

  11. Technology computer aided design for Si, SiGe and GaAs integrated circuits

    CERN Document Server

    Armstrong, GA

    2007-01-01

    The first book to deal with a broad spectrum of process and device design, and modelling issues related to semiconductor devices, bridging the gap between device modelling and process design using TCAD. Examples for types of Si-, SiGe-, GaAs- and InP-based heterostructure MOS and bipolar transistors are compared with experimental data from state-of-the-art devices. With various aspects of silicon heterostructures, this book presents a comprehensive perspective of emerging fields and covers topics ranging from materials to fabrication, devices, modelling and applications. Aimed at research-and-

  12. Coulomb interaction of electron gas in MQWs Si/Si{sub 1-x}Ge{sub x}/Si

    Energy Technology Data Exchange (ETDEWEB)

    Sfina, N. [Unite de Physique des Solides, Departement de Physique, Faculte des Sciences de Monastir, Avenue de l' Environnement, 5019 Monastir (Tunisia)], E-mail: sfina_fsm@yahoo.fr; Lazzari, J.-L. [Centre de Recherche en Matiere Condensee et Nanosciences, CRMC-N, UPR-CNRS 7251, Laboratory associated with the Universite de la Mediterranee and the Universite Paul Cezanne, Campus de Luminy, Case 913, 13288 Marseille cedex 9 (France); Cuminal, Y.; Christol, P. [Centre d' Electronique et de Micro-optoelectronique de Montpellier, CEM2, UMR-CNRS 5507, Universite Montpellier 2 - Sciences et Techniques du Languedoc, CC 067, Place Eugene Bataillon, 34095 Montpellier cedex 5 (France); Said, M. [Unite de Physique des Solides, Departement de Physique, Faculte des Sciences de Monastir, Avenue de l' Environnement, 5019 Monastir (Tunisia)], E-mail: moncef_said@yahoo.fr

    2008-07-01

    We present a theoretical analysis of the conduction and valence-band diagrams of SiGe/Si Multiple Quantum Wells (MQWs), having a specific 'W' geometry, and designed for emission or photodetection around the 1.55 {mu}m wavelength. Peculiar features have been extrapolated by solving self-consistent Schroedinger and Poisson equations, taking into account the electrostatic attraction induced by carrier injection. As a result, Coulomb interaction strongly modifies the band profiles and increases the electron probability density at the quantum well interfaces; the injected carrier concentration enhances electron-hole wave functions overlap and the in-plane oscillator strength. These MQWs structures, strain-compensated on relaxed Si{sub 0.75}Ge{sub 0.25} pseudo-substrates, are potentially interesting for telecom applications.

  13. Structural evolution of Ge-rich Si{sub 1−x}Ge{sub x} films deposited by jet-ICPCVD

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu; Yang, Meng; Wang, Gang [Key Laboratory of Advanced Photonic and Electronic Materials and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Wei, Xiaoxu; Wang, Junzhuan; Li, Yun; Zheng, Youdou; Shi, Yi, E-mail: yshi@nju.edu.cn [Key Laboratory of Advanced Photonic and Electronic Materials and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Micro-structures, Nanjing University, Nanjing 210093 (China); Zou, Zewen [College of Physics and Electronics Information, Anhui Normal University, Wuhu 241000 (China)

    2015-11-15

    Amorphous Ge-rich Si{sub 1−x}Ge{sub x} films with local Ge-clustering were deposited by dual-source jet-type inductively coupled plasma chemical-vapor deposition (jet-ICPCVD). The structural evolution of the deposited films annealed at various temperatures (Ta) is investigated. Experimental results indicate that the crystallization occurs to form Ge and Si clusters as Ta = 500 °C. With raising Ta up to 900 °C, Ge clusters percolate together and Si diffuses and redistributes to form a Ge/SiGe core/shell structure, and some Ge atoms partially diffuse to the surface as a result of segregation. The present work will be helpful in understanding the structural evolution process of a hybrid SiGe films and beneficial for further optimizing the microstructure and properties.

  14. Research Advance on Magnetocaloric Effect of La-Fe-M(Al, Si) Compounds

    Institute of Scientific and Technical Information of China (English)

    肖素芬; 陈云贵; 郝春; 吴金平; 涂铭旌

    2004-01-01

    Recent research progress on magnetocaloric effect of La-Fe-M(M=Al,Si)compounds was presented.La-Fe-M(M=Al,Si)compounds of high Fe content are excellent soft magnetic materials with NaZn13 structure.The Curie temperature of the compounds can be increased by substituting small amount of Co for Si,Al.The La(Fe1-yCoy)xSi13-x compounds with an appropriate ratio of Co and Si can produce giant magnetocaloric effect comparable to that for Gd5Si2Ge2 at room temperature.The La(FexSi1-x)13 doped with H can also produce giant magnetocaloric effect at room temperature,which is much greater than that for Gd.For La(FexSi1-x)13 compounds with low Si or high Si contents.The nature of phase transition near Curie temperature induced by temperature and magnetic field was described in detail.

  15. FABRICATION OF STRAINED-Si CHANNEL P-MOSFET's ON ULTRA-THIN SiGe VIRTUAL SUBSTRATES

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In the ultra-thin relaxed SiGe virtual substrates, a strained-Si channel p-type Metal Oxide Semi-conductor Field Effect Transistor (p-MOSFET) is presented. Built on strained-Si/240nm relaxed-Si0.8 Ge0.2/100nm Low Temperature Si (LT-Si)/10nm Si buffer was grown by Molecular Beam Epitaxy (MBE), in whichLT-Si layer is used to release stress of the SiGe layer and made it relaxed. Measurement indicates that thestrained-Si p-MOSFET's (L=4.2μm) transconductance and the hole mobility are enhanced 30% and 50% re-spectively, compared with that of conventional bulk-Si. The maximum hole mobility for strained-Si device is140cm2/Vs. The device performance is comparable to devices achieved on several μm thick compositiongraded buffers and relaxed-SiGe layer virtual substrates.

  16. Direct growth of Ge quantum dots on a graphene/SiO2/Si structure using ion beam sputtering deposition.

    Science.gov (United States)

    Zhang, Z; Wang, R F; Zhang, J; Li, H S; Zhang, J; Qiu, F; Yang, J; Wang, C; Yang, Y

    2016-07-29

    The growth of Ge quantum dots (QDs) using the ion beam sputtering deposition technique has been successfully conducted directly on single-layer graphene supported by SiO2/Si substrate. The results show that the morphology and size of Ge QDs on graphene can be modulated by tuning the Ge coverage. Charge transfer behavior, i.e. doping effect in graphene has been demonstrated at the interface of Ge/graphene. Compared with that of traditional Ge dots grown on Si substrate, the positions of both corresponding photoluminescence (PL) peaks of Ge QDs/graphene hybrid structure undergo a large red-shift, which can probably be attributed to the lack of atomic intermixing and the existence of surface states in this hybrid material. According to first-principles calculations, the Ge growth on the graphene should follow the so-called Volmer-Weber mode instead of the Stranski-Krastanow one which is observed generally in the traditional Ge QDs/Si system. The calculations also suggest that the interaction between Ge and graphene layer can be enhanced with the decrease of the Ge coverage. Our results may supply a prototype for fabricating novel optoelectronic devices based on a QDs/graphene hybrid nanostructure.

  17. Simultaneous suppression of ferromagnetism and superconductivity in UCoGe by Si substitution

    NARCIS (Netherlands)

    de Nijs, D.E.; Huy, N.T.; de Visser, A.

    2008-01-01

    We investigate the effect of substituting Si for Ge in the ferromagnetic superconductor UCoGe. dc-magnetization, ac-susceptibility, and electrical resistivity measurements on polycrystalline UCoGe1-xSix samples show that ferromagnetic order and superconductivity are progressively depressed with incr

  18. Synthesis of crystalline Ge nanoclusters in PE-CVD-deposited SiO2 films

    DEFF Research Database (Denmark)

    Leervad Pedersen, T.P.; Skov Jensen, J.; Chevallier, J.

    2005-01-01

    The synthesis of evenly distributed Ge nanoclusters in plasma-enhanced chemical-vapour-deposited (PE-CVD) SiO2 thin films containing 8 at. % Ge is reported. This is of importance for the application of nanoclusters in semiconductor technology. The average diameter of the Ge nanoclusters can...

  19. Low temperature growth of heavy boron-doped hydrogenated Ge epilayers and its application in Ge/Si photodetectors

    Science.gov (United States)

    Kuo, Wei-Cheng; Lee, Ming Jay; Wu, Mount-Learn; Lee, Chien-Chieh; Tsao, I.-Yu; Chang, Jenq-Yang

    2017-04-01

    In this study, heavily boron-doped hydrogenated Ge epilayers are grown on Si substrates at a low growth temperature (220 °C). The quality of the boron-doped epilayers is dependent on the hydrogen flow rate. The optical emission spectroscopic, X-ray diffraction and Hall measurement results demonstrate that better quality boron-doped Ge epilayers can be obtained at low hydrogen flow rates (0 sccm). This reduction in quality is due to an excess of hydrogen in the source gas, which breaks one of the Ge-Ge bonds on the Ge surface, leading to the formation of unnecessary dangling bonds. The structure of the boron doped Ge epilayers is analyzed by transmission electron microscopy and atomic force microscopy. In addition, the performance, based on the I-V characteristics, of Ge/Si photodetectors fabricated with boron doped Ge epilayers produced under different hydrogen flow rates was examined. The photodetectors with boron doped Ge epilayers produced with a low hydrogen flow rate (0 sccm) exhibited a higher responsivity of 0.144 A/W and a lower dark current of 5.33 × 10-7 A at a reverse bias of 1 V.

  20. Photoconductivity of ultra-thin Ge(GeSn) layers grown in Si by low-temperature molecular beam epitaxy

    Science.gov (United States)

    Talochkin, A. B.; Chistokhin, I. B.; Mashanov, V. I.

    2016-04-01

    Photoconductivity (PC) spectra of Si/Ge(GeSn)/Si structures with the ultra-thin (1.0-2.3 nm) Ge and GeSn alloy layers grown by the low-temperature (T = 100 °C) molecular beam epitaxy are studied. Photoresponse in the range of 1.2-0.4 eV related to light absorption in the buried Ge(GeSn) layer is observed. It is shown that in case of lateral PC, a simple diffusion model can be used to determine the absorption coefficient of this layer α ˜ 105 cm-1. This value is 100 times larger than that of a single Ge quantum dot layer and is reached significantly above the band gap of most bulk semiconductors. The observed absorption is caused by optical transitions between electron and hole states localized at the interfaces. The anomalous high value of α can be explained by the unusual state of Ge(GeSn) layer with high concentration of dangling bonds, the optical properties of which have been predicted theoretically by Knief and von Niessen (Phys. Rev. B 59, 12940 (1999)).

  1. Formation of Ge{sup 0} and GeO{sub x} nanoclusters in Ge{sup +}-implanted SiO{sub 2}/Si thin-film heterostructures under rapid thermal annealing

    Energy Technology Data Exchange (ETDEWEB)

    Zatsepin, A.F., E-mail: a.f.zatsepin@urfu.ru [Institute of Physics and Technology, Ural Federal University, Mira Str. 19, 620002 Yekaterinburg (Russian Federation); Zatsepin, D.A. [Institute of Physics and Technology, Ural Federal University, Mira Str. 19, 620002 Yekaterinburg (Russian Federation); Institute of Metal Physics, Russian Academy of Sciences – Ural Division, S. Kovalevskoi Str. 18, 620990 Yekaterinburg (Russian Federation); Institute of Physics, Polish Academy of Science, 02-668 Warsaw (Poland); Zhidkov, I.S. [Institute of Physics and Technology, Ural Federal University, Mira Str. 19, 620002 Yekaterinburg (Russian Federation); Kurmaev, E.Z. [Institute of Physics and Technology, Ural Federal University, Mira Str. 19, 620002 Yekaterinburg (Russian Federation); Institute of Metal Physics, Russian Academy of Sciences – Ural Division, S. Kovalevskoi Str. 18, 620990 Yekaterinburg (Russian Federation); Fitting, H.-J. [Institute of Physics, University of Rostock, D-18051 Rostock (Germany); Schmidt, B. [Institute of Ion Beam Physics, Research Center Dresden-Rossendorf, POB 510119, 01314 Dresden (Germany); Mikhailovich, A.P. [Institute of Physics and Technology, Ural Federal University, Mira Str. 19, 620002 Yekaterinburg (Russian Federation); Lawniczak-Jablonska, K. [Institute of Physics, Polish Academy of Science, 02-668 Warsaw (Poland)

    2015-09-15

    Highlights: • Results of XPS for valence and core levels of Ge implanted SiO{sub 2} films are presented. • Chemical-state transformation of the host-matrix composition and Ge ions is performed. • The rapid thermal annealing strongly affects the oxidation states of Ge-atoms. • The formation of Ge{sup 0} and GeO{sub x} clusters within subsurface layer is observed. - Abstract: The results of X-ray photoelectron spectra (XPS valence band and core levels) measurements for Ge{sup +} implanted SiO{sub 2}/Si heterostructures are presented. These heterostructures have a 30 nm thick Ge{sup +} ion implanted amorphous SiO{sub 2} layer on p-type Si. The chemical-state transformation of the host-matrix composition after Ge{sup +} ion implantation and rapid thermal annealing (RTA) are discussed. The XPS-analysis performed allows to conclude the formation of Ge{sup 0} and GeO{sub x} clusters within the samples under study. It was established, that the annealing time strongly affects the degree of oxidation states of Ge-atoms.

  2. Type 2 quantum dots in Ge/Si system

    CERN Document Server

    Dvurechenskij, A V

    2001-01-01

    The results on the electronic structure of spatially indirect excitons, multiparticle excitonic complexes, and negative interband photoconductivity in arrays of Ge/Si type 2 quantum dots are presented. These data have been compared with the well known results for type 2 A sup I sup I sup I B sup V and A sup I sup I B sup V sup I -based heterostructures with quantum dots. Fundamental physical phenomena are found to be the result of an increase in the binding energy of excitons in quantum dots as compared with that of free excitons in bulk homogeneous materials; the shortwave shift of exciton transition energy at multiparticle complexes production (charges excitons, biexcitons), as well as the trapping of equilibrium carrier by localized states induced by the charged quantum dot electric field

  3. Atomic Layer Deposition of Al2O3 on H-Passivated GeSi: Initial Surface Reaction Pathways with H/GeSi(100)-2 × 1

    Institute of Scientific and Technical Information of China (English)

    SHI Yu; SUN Qing-Qing; DONG Lin; LIU Han; DING Shi-Jin; ZHANG Wei

    2009-01-01

    The reaction mechanisms of Al(CH3 )3 (TMA ) adsorption on H-passivated GeSi(l O0)-2 × 1 surface are investigated with density functional theory. The Si-Ge and Ge-Ge one-dimer duster models are employed to represent the GeSi(100)-2 × 1 surface with different Ge compositions. For a Si-Ge dimer of a H-passivated SiGe surface, TMA adsorption on both Si-H* and Ge-H* sites is considered. The activation barrier of TMA with the Si-H* site (1.2eV) is higher than that of TMA with the Ge-H* site (0.91 eV), which indicates that the reaction proceeds more slowly on the Si-H* site than on the Ge-H* site. In addition, adsorption of TMA is more energetically favorable on the Ge-Ge dimer than on the Si-Ge dimer of H-passivated SiGe.

  4. Improvement of High Temperature Characteristics for SiGeC p-i-n Diodes with Carbon Incorporation

    Institute of Scientific and Technical Information of China (English)

    GAO Yong; LIU Jing; YANG Yuan

    2008-01-01

    Temperature-dependent characteristics of SiGeC p-i-n diodes are analysed and discussed. Based on the ISE data, the temperature-dependent physical models applicable for SiGeC/Si diodes are presented. Due to the addition of carbon into the SiGe system, the thermal stability of SiGeC diodes are improved remarkably. Compared to SiGe diodes, the reverse leakage current of SiGeC diodes is decreased by 97.1% at 400 K and its threshold voltage shift is reduced over 65.3% with an increasing temperature from 300 K to 400 K. Furthermore, the fast and soft reverse recovery characteristics are also obtained at 400 K for SiGeC diodes. As a result, the most remarkable feature of SiGeC diodes is the better high-temperature characteristics and this can be applied to high temperature up to 400 K.

  5. Source/drain eSiGe engineering for FinFET technology

    Science.gov (United States)

    Peng, Jianwei; Qi, Yi; Lo, Hsien-Ching; Zhao, Pei; Yong, Chloe; Yan, Jianghu; Dou, Xinyuan; Zhan, Hui; Shen, Yanping; Regonda, Suresh; Hu, Owen; Yu, Hong; Joshi, Manoj; Adams, Charlotte; Carter, Rick; Samavedam, Srikanth

    2017-09-01

    Epitaxy growth loading effect—the growth rate difference between device macros due to their local open ratio difference—is an important consideration for device design and thus process optimization. A poor loading process leads to device performance delta across macros. For eSiGe on FinFETs, we found that optimized eSiGe on FinFETs saturates as the eSiGe diamond pins at fin top surface and the fin-sidewall-spacer (FSS). The eSiGe diamond size measured by lateral CD does not increase with deposition time, but it linearly correlates to cavity depth and FSS pushdown. In principle, the eSiGe loading effect can be addressed with an extended growth time until every device macros saturates. However, it is found that, the epitaxy growth related defects, measured by abnormal eSiGe and unwanted growth, can also be elevated to an unacceptable level for a longer deposition time. Thus, the eSiGe loading process still needs to be optimized for an improved process window. In this work, an optimized eSiGe process achieves reduced loading between 2-fin and 40-fin macros and thus a smaller pFET performance gap between the two device macros.

  6. Formation of GeSn alloy on Si(100) by low-temperature molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Talochkin, A. B., E-mail: tal@isp.nsc.ru [A. V. Rzhanov Institute of Semiconductor Physics, Lavrentyev Avenue 13, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Mashanov, V. I. [A. V. Rzhanov Institute of Semiconductor Physics, Lavrentyev Avenue 13, Novosibirsk 630090 (Russian Federation)

    2014-12-29

    GeSn alloys grown on Si(100) by the low-temperature (100 °C) molecular beam epitaxy are studied using scanning tunneling microscopy and Raman spectroscopy. It is found that the effect of Sn as a surfactant modifies substantially the low-temperature growth mechanism of Ge on Si. Instead of the formation of small Ge islands surrounded by amorphous Ge, in the presence of Sn, the growth of pure Ge islands appears via the Stranski-Krastanov growth mode, and a partially relaxed Ge{sub 1−x}Sn{sub x} alloy layer with the high Sn-fraction up to 40 at. % is formed in the area between them. It is shown that the observed growth mode induced by high surface mobility of Sn and the large strain of the pseudomorphic state of Ge to Si ensures the minimum elastic-strain energy of the structure.

  7. High-Quality Single Crystalline Ge(111) Growth on Si(111) Substrates by Solid Phase Epitaxy

    Institute of Scientific and Technical Information of China (English)

    SUN Bing; CHANG Hu-Dong; LU Li; LIU Hong-Gang; WU De-Xin

    2012-01-01

    Heterogeneous integration of crystalline Ge layers on cleaned and H-terminated Si(111) substrates are demonstrated by employing a combination of e-beam evaporation and solid phase epitaxy techniques. High-quality single crystalline Ge(111) layers on Si(111) substrates with a smooth Ge surface and an abrupt interface between Ge and Si are obtained.An XRD rocking curve scan of the Ge(111) diffraction peak shovs a FWHM of only 260 arcsec for a 50-nm-thick Ge layer annealed at 600℃ with a ramp-up rate of 20℃/s and a holding time of 1 min. The AFM images exhibit that the rms surface roughness of all the crystalline Ge layers are less than 2.1 nm.

  8. Influence of Containment on Defects in GeSi Crystals

    Science.gov (United States)

    Volz, M. P.; Croell, A.; Mazuruk, K.

    2009-01-01

    Crystals grown without being in contact with a container have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. "Detached" or "dewetted" Bridgman growth is similar to regular Bridgman growth in that most of the melt is in contact with the crucible wall, but the crystal is separated from the wall by a small gap, typically of the order of 10(exp -5) m. A small meniscus bridges the gap between the top of the crystal and the wall. Key parameters involved in achieving detached growth are the contact angle between the melt and crucible and the pressure differential across the meniscus. Sessile drop measurements were used to determine the wetting angles of Ge(sub 1-x)Si(sub x) melts on a variety of substrates and found that the highest wetting angles were achieved with pyrolitic boron nitride (pBN). GeSi crystals have been repeatedly grown detached in pBN crucibles but only occasionally in crucibles with lower wetting angles. Experiments have been conducted to assess the effect of pressure differential across the meniscus in sealed crucibles. This was done by adjusting the temperature profile after partial melting of the starting material. In a separate set of experiments, the pressure was controlled by connecting the volume below the meniscus to a regulated gas supply. The experiments were in agreement with calculations which predicted that stable detachment will only occur in crucibles with a low wetting angle over a relatively narrow range of pressure differential. Detached-grown crystals exhibited superior structural quality as evidenced by measurements of etch pit density, synchrotron white beam X-ray topography and double axis X-ray diffraction.

  9. Surface Roughness and Dislocation Distribution in Compositionally Graded Relaxed SiGe Buffer Layer with Inserted Strained Si Layers

    Science.gov (United States)

    Yoon, Tae-Sik

    2005-03-01

    We report the experimental investigation of surface roughness and dislocation distribution of 1 μm-thick, compositionally graded, relaxed SiGe buffer layer with a final Ge surface content of 30%. Tensile-strained Si layers are inserted at various locations in the graded buffer during SiGe epitaxial growths. Slight reduction in surface roughness from about 10.3 nm to about 7.8 nm by inserting two 20 nm thick tensile-strained Si layers followed by SiGe growths. It turns out that majority of the residual surface roughness is developed during the SiGe growths on top of the topmost strain Si layer. The surface immediately after the growth of tensile strained Si is very flat with about 1.1 nm RMS roughness and without crosshatch morphology. Cross-sectional TEM shows clear signs of increased interaction between dislocation half-loops at the top surface of the strained Si layers. Our observation shows that although thin Si layers under tensile-strain are effective in reducing cross-hatch, they could in the meantime impede dislocation propagation leading to higher threading dislocation density. Considerations for an optimized scheme exploiting the flattening function of tensile-strained layers will be discussed.

  10. Ultra-low temperature (≤300 °C) growth of Ge-rich SiGe by solid-liquid-coexisting annealing of a-GeSn/c-Si structures

    Science.gov (United States)

    Sadoh, Taizoh; Chikita, Hironori; Matsumura, Ryo; Miyao, Masanobu

    2015-09-01

    Ultra-low temperature (≤300 °C) growth of Ge-rich SiGe on Si substrates is strongly desired to realize advanced electronic and optical devices, which can be merged onto Si large-scale integrated circuits (LSI). To achieve this, annealing characteristics of a-GeSn/c-Si structures are investigated under wide ranges of the initial Sn concentrations (0%-26%) and annealing conditions (300-1000 °C, 1 s-48 h). Epitaxial growth triggered by SiGe mixing is observed after annealing, where the annealing temperatures necessary for epitaxial growth significantly decrease with increasing initial Sn concentration and/or annealing time. As a result, Ge-rich (˜80%) SiGe layers with Sn concentrations of ˜2% are realized by ultra-low temperature annealing (300 °C, 48 h) for a sample with the initial Sn concentration of 26%. The annealing temperature (300 °C) is in the solid-liquid coexisting temperature region of the phase diagram for Ge-Sn system. From detailed analysis of crystallization characteristics and composition profiles in grown layers, it is suggested that SiGe mixing is generated by a liquid-phase reaction even at ultra-low temperatures far below the melting temperature of a-GeSn. This ultra-low-temperature growth technique of Ge-rich SiGe on Si substrates is expected to be useful to realize next-generation LSI, where various multi-functional devices are integrated on Si substrates.

  11. Ultra-low temperature (≤300 °C) growth of Ge-rich SiGe by solid-liquid-coexisting annealing of a-GeSn/c-Si structures

    Energy Technology Data Exchange (ETDEWEB)

    Sadoh, Taizoh, E-mail: sadoh@ed.kyushu-u.ac.jp; Chikita, Hironori; Miyao, Masanobu [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Matsumura, Ryo [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); JSPS Research Fellow, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan)

    2015-09-07

    Ultra-low temperature (≤300 °C) growth of Ge-rich SiGe on Si substrates is strongly desired to realize advanced electronic and optical devices, which can be merged onto Si large-scale integrated circuits (LSI). To achieve this, annealing characteristics of a-GeSn/c-Si structures are investigated under wide ranges of the initial Sn concentrations (0%–26%) and annealing conditions (300–1000 °C, 1 s–48 h). Epitaxial growth triggered by SiGe mixing is observed after annealing, where the annealing temperatures necessary for epitaxial growth significantly decrease with increasing initial Sn concentration and/or annealing time. As a result, Ge-rich (∼80%) SiGe layers with Sn concentrations of ∼2% are realized by ultra-low temperature annealing (300 °C, 48 h) for a sample with the initial Sn concentration of 26%. The annealing temperature (300 °C) is in the solid-liquid coexisting temperature region of the phase diagram for Ge-Sn system. From detailed analysis of crystallization characteristics and composition profiles in grown layers, it is suggested that SiGe mixing is generated by a liquid-phase reaction even at ultra-low temperatures far below the melting temperature of a-GeSn. This ultra-low-temperature growth technique of Ge-rich SiGe on Si substrates is expected to be useful to realize next-generation LSI, where various multi-functional devices are integrated on Si substrates.

  12. A novel predictive model for formation enthalpies of Si and Ge hydrides with propane- and butane-like structures.

    Science.gov (United States)

    Weng, C; Kouvetakis, J; Chizmeshya, A V G

    2011-04-15

    Butane- and propane-like silicon-germanium hydrides and chlorinated derivatives represent a new class of precursors for the fabrication of novel metastable materials at low-temperature regimes compatible with selective growth and commensurate with the emerging demand for the reduced thermal budgets of complementary metal oxide semiconductor integration. However, predictive simulation studies of the growth process and reaction mechanisms of these new compounds, needed to accelerate their deployment and fine-tune the unprecedented low-temperature and low-pressure synthesis protocols, require experimental thermodynamic data, which are currently unavailable. Furthermore, traditional quantum chemistry approaches lack the accuracy needed to treat large molecules containing third-row elements such as Ge. Accordingly, here we develop a method to accurately predict the formation enthalpy of these compounds using atom-wise corrections for Si, Ge, Cl, and H. For a test set of 15 well-known hydrides of Si and Ge and their chlorides, such as Si(3)H(8), Ge(2)H(6), SiGeH(6), SiHCl(3), and GeCl(4), our approach reduces the deviations between the experimental and predicted formation enthalpies obtained from complete basis set (CBS-QB3), G2, and B3LPY thermochemistry to levels of 1-3 kcal/mol, or a factor of ∼5 over the corresponding uncorrected values. We show that our approach yields results comparable or better than those obtained using homodesmic reactions while circumventing the need for thermochemical data of the associated reaction species. Optimized atom-wise corrections are then used to generate accurate enthalpies of formation for 39 pure Si-Ge hydrides and a selected group of 20 chlorinated analogs, of which some have recently been synthesized for the first time. Our corrected enthalpies perfectly reproduce the experimental stability trends of heavy butane-like compounds containing Ge. This is in contrast to the direct application of the CBS-QB3 method, which yields

  13. Quantum-Confined Stark Effect Analysis of GeSn/SiGeSn Quantum Wells for Mid-Infrared Si-Based Electroabsorption Devices Based on Many-Body Theory

    OpenAIRE

    Fujisawa, Takeshi; Saitoh, Kunimasa

    2015-01-01

    Quantum-confined Stark effect (QCSE) of group IV Ge(Sn)/SiGe(Sn) quantum wells (QWs) on Si substrate is analyzed by microscopic many-body theory for mid-infrared (mid-IR) Si-based electroabsorption devices. To show the validity of the theory, QCSE of Ge/SiGe QW is investigated and very good agreement between theory and reported measured results is obtained. Next, the QCSE of GeSn/SiGeSn QWs is analyzed and the QW design for electroabsorption modulators to obtain large extinction ratio in mid-...

  14. Investigation on the strain of SiGe/Si heteroepitaxial system during high temperature annealing by RBS/Channeling

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The influence of the high temperature processing on the strain stored in SiGe hetero epilayer was studied by means of RBS/Channeling. Channeling angularscan along the < 110 > axial direction in the (100) plane was used to characterize the tetragonal distortion in the SiGe strained layer. The strained crystal structure parameters were acquired by combining the determination of strain with the elasticity theory. It is shown that the strain stored in the SiGe epilayer has significantly change (relaxation factor from 0.023 to 0.84) after high temperature annealing. The potential strain relaxation mechanisms were discussed.

  15. Spin relaxation in Si nanoclusters embedded in free-standing SiGe nanocolumns

    Science.gov (United States)

    Stepina, N. P.; Zinovieva, A. F.; Dvurechenskii, A. V.; Noda, Shuichi; Molla, Md. Zaman; Samukawa, Seiji

    2017-05-01

    Separated nanocolumns (NCs) with embedded Si nanoclusters were prepared using the top-down technique that combines a bio-template and the defect-free neutral beam etching of Si0.75Ge0.25/Si/Si0.75Ge0.25 double-quantum-well layers. The electron spin resonance (ESR) was studied in the dark and under illumination for the structures with different lateral sizes of NCs. For the structure with a NC diameter in the range of 20-25 nm, the ESR signal is characterized by the isotropic line width. The spatial separation of nanoclusters results in the suppression of the Dyakonov-Perel mechanism of spin relaxation. A decrease in the NC diameter down to 13-14 nm leads to electron localization under the bottom of NCs, making the orientation dependence of the ESR line width anisotropic. Illumination results in the increase in spin lifetimes in both the types of NC structures, relocating the electrons to the center of NCs in the narrow NC structure, and making electron localization stronger in the thick NCs.

  16. Cryogenic operation of a 24 GHz MMIC SiGe HBT medium power amplifier

    Science.gov (United States)

    Qin, Guoxuan; Jiang, Ningyue; Seo, Jung-Hun; Cho, Namki; Ponchak, George E.; van der Weide, Daniel; Ma, Pingxi; Stetson, Scott; Racanelli, Marco; Ma, Zhenqiang

    2010-12-01

    The performance of a SiGe heterojunction bipolar transistor (HBT) millimetre-wave power amplifier (PA) operating at cryogenic temperature was reported and analysed for the first time. A 24 GHz two-stage medium PA employing common-emitter and common-base SiGe power HBTs in the first and the second stage, respectively, showed a significant power gain increase at 77 K in comparison with that measured at room temperature. Detailed analyses indicate that cryogenic operation of SiGe HBT-based PAs mainly affects (improves) the performance of the SiGe HBTs in the circuits due to transconductance enhancement through magnified, favourable changes of SiGe bandgap due to cooling (ΔEg/kT) and minimized thermal effects, with little influence on the passive components of the circuits.

  17. Interface bond relaxation on the thermal conductivity of Si/Ge core-shell nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Weifeng; He, Yan; Ouyang, Gang, E-mail: gangouy@hunnu.edu.cn [Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Synergetic Innovation Center for Quantum Effects and Applications(SICQEA), Hunan Normal University, Changsha 410081 (China); Sun, Changqing [School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2016-01-15

    The thermal conductivity of Si/Ge core-shell nanowires (CSNWs) is investigated on the basis of atomic-bond-relaxation consideration and continuum mechanics. An analytical model is developed to clarify the interface bond relaxation of Si/Ge CSNWs. It is found that the thermal conductivity of Si core can be modulated through covering with Ge epitaxial layers. The change of thermal conductivity in Si/Ge CSNWs should be attributed to the surface relaxation and interface mismatch between inner Si nanowire and outer Ge epitaxial layer. Our results are in well agreement with the experimental measurements and simulations, suggesting that the presented method provides a fundamental insight of the thermal conductivity of CSNWs from the atomistic origin.

  18. Interface bond relaxation on the thermal conductivity of Si/Ge core-shell nanowires

    Directory of Open Access Journals (Sweden)

    Weifeng Chen

    2016-01-01

    Full Text Available The thermal conductivity of Si/Ge core-shell nanowires (CSNWs is investigated on the basis of atomic-bond-relaxation consideration and continuum mechanics. An analytical model is developed to clarify the interface bond relaxation of Si/Ge CSNWs. It is found that the thermal conductivity of Si core can be modulated through covering with Ge epitaxial layers. The change of thermal conductivity in Si/Ge CSNWs should be attributed to the surface relaxation and interface mismatch between inner Si nanowire and outer Ge epitaxial layer. Our results are in well agreement with the experimental measurements and simulations, suggesting that the presented method provides a fundamental insight of the thermal conductivity of CSNWs from the atomistic origin.

  19. Noise Parameter Analysis of SiGe HBTs for Different Sizes in the Breakdown Region

    Directory of Open Access Journals (Sweden)

    Chie-In Lee

    2016-01-01

    Full Text Available Noise parameters of silicon germanium (SiGe heterojunction bipolar transistors (HBTs for different sizes are investigated in the breakdown region for the first time. When the emitter length of SiGe HBTs shortens, minimum noise figure at breakdown decreases. In addition, narrower emitter width also decreases noise figure of SiGe HBTs in the avalanche region. Reduction of noise performance for smaller emitter length and width of SiGe HBTs at breakdown resulted from the lower noise spectral density resulting from the breakdown mechanism. Good agreement between experimental and simulated noise performance at breakdown is achieved for different sized SiGe HBTs. The presented analysis can benefit the RF circuits operating in the breakdown region.

  20. Standard molar enthalpy of formation of FeGe(s) and FeGe{sub 2}(s) intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Phapale, S. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Mishra, R., E-mail: mishrar@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Chattaraj, D.; Samui, P. [Product Development Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Sengupta, P. [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Mishra, P.K. [Technical Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2014-04-05

    Highlights: • FeGe(s) and FeGe{sub 2}(s) have been synthesized and characterized. • The heat of dissolutions of Fe(s), Ge(s), FeGe(s) and FeGe2(s) in liquid tin have been measured. • Δ{sub f}H{sub 298}{sup °} of FeGe, FeGe{sub 2} were found to be to −15.56 ± 0.92 and −36.89 ± 1.17 kJ mol{sup −1}, respectively. -- Abstract: Thermodynamics plays an important role in predicting long term stability of the materials under different reactive conditions. The present paper describes determination of standard molar enthalpies of formation of FeGe(s) and FeGe{sub 2}(s) compounds employing a high temperature solution calorimeter. The reaction enthalpies of Fe(s), Ge(s), FeGe(s) and FeGe{sub 2}(s) in liquid Sn at 986 K were measured using a Calvet calorimeter. The standard molar enthalpy of formation of the compounds at 298 K (Δ{sub f}H{sub 298}{sup °}) were calculated using the measured reaction enthalpy data. The values of Δ{sub f}H{sub 298}{sup °} of FeGe(s) and FeGe{sub 2}(s) at 298 K were found to −15.56 ± 0.92 and −36.89 ± 1.17 kJ mol{sup −1}, respectively. The standard molar enthalpy of formation of FeGe(s) and FeGe{sub 2}(s) at 298 K obtained experimentally has been compared with the calculated values derived using Vienna ab initio simulation package (VASP)

  1. Magnetic properties of the RCo {sub x}Ge{sub 2} (R = Gd-Er) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Baran, S. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Cracow (Poland); Henkel, F. [BENSC, Hahn-Meitner Institut, Glienicker Strasse 100, D-14109 Berlin-Wannsee (Germany); Kaczorowski, D. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland); Hernandez-Velasco, J. [BENSC, Hahn-Meitner Institut, Glienicker Strasse 100, D-14109 Berlin-Wannsee (Germany); Penc, B. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Cracow (Poland); Stuesser, N. [BENSC, Hahn-Meitner Institut, Glienicker Strasse 100, D-14109 Berlin-Wannsee (Germany); Szytula, A. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Cracow (Poland)]. E-mail: szytula@if.uj.edu.pl; Wawrzynska, E. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Cracow (Poland)

    2006-05-18

    Magnetization, magnetic susceptibility, X-ray and neutron diffraction measurements down to 1.5 K were performed on polycrystalline RCo {sub x}Ge{sub 2} (R Gd-Er) samples, in which x = 0.4-0.5. All of them crystallize in the orthorhombic structure of the CeNiSi{sub 2}-type. The compounds were found to order antiferromagnetically at low temperatures except for the Tb and Dy samples, in which no magnetic contributions were observed in the neutron diffraction patterns recorded at 1.5 K although transitions are visible in the temperature dependences of the magnetic susceptibility of these compounds. In the case of HoCo{sub 0.4}Ge{sub 2} magnetic order appearing below the Neel temperature of 8 K is described by the propagation vector k = (1/2, 1/2, 0) and for the ErCo {sub x}Ge{sub 2} compounds at 1.5 K the structure is described by k = (k {sub x}, k {sub x}, 0). The value of the k {sub x} component depends on the concentration x.

  2. Optical absorption in highly strained Ge/SiGe quantum wells: The role of Γ→ Δ scattering

    Science.gov (United States)

    Lever, L.; Ikonić, Z.; Valavanis, A.; Kelsall, R. W.; Myronov, M.; Leadley, D. R.; Hu, Y.; Owens, N.; Gardes, F. Y.; Reed, G. T.

    2012-12-01

    We report the observation of the quantum-confined Stark effect in Ge/SiGe multiple quantum well heterostructures grown on Si0.22Ge0.78 virtual substrates. The large compressive strain in the Ge quantum well layers caused by the lattice mismatch with the virtual substrate results in a blue shift of the direct absorption edge, as well as a reduction in the Γ-valley scattering lifetime because of strain-induced splittings of the conduction band valleys. We investigate theoretically the Γ-valley carrier lifetimes by evaluating the Γ →L and Γ →Δ scattering rates in strained Ge/SiGe semiconductor heterostructures. These scattering rates are used to determine the lifetime broadening of excitonic peaks and the indirect absorption in simulated absorption spectra, which are compared with measured absorption spectra for quantum well structures with systematically varied dimensions. We find that Γ →Δ scattering is significant in compressively strained Ge quantum wells and that the Γ-valley electron lifetime is less than 50 fs in the highly strained structures reported here, where Γ →Δ scattering accounted for approximately half of the total scattering rate.

  3. Investigations of the R5(SixGe1-x)4 Intermetallic Compounds by X-Ray Resonant Magnetic Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Lizhi [Iowa State Univ., Ames, IA (United States)

    2008-08-18

    The XRMS experiment on the Gd5Ge4 system has shown that, below the Neel temperature, TN = 127 K, the magnetic unit cells is the same as the chemical unit cell. From azimuth scans and the Q dependence of the magnetic scattering, all three Gd sites in the structure were determined to be in the same magnetic space group Pnma. The magnetic moments are aligned along the c-axis and the c-components of the magnetic moments at the three different sites are equal. The ferromagnetic slabs are stacked antiferromagnetically along the b-direction. They found an unusual order parameter curve in Gd5Ge4. A spin-reorientation transition is a possibility in Gd5Ge4, which is similar to the Tb5Ge4 case. Tb5Ge4 possesses the same Sm5Ge4-type crystallographic structure and the same magnetic space group as Gd5Ge4 does. The difference in magnetic structure is that Tb5Ge4 has a canted one but Gd5Ge4 has nearly a collinear one in the low temperature antiferromagnetic phase. The competition between the magneto-crystalline anisotropy and the nearest-neighbor magnetic exchange interactions may allow a 3-dimensional canted antiferromagnetic structure in Tb5Ge4. The spin-reorientation transition in both Gd5Ge4 and Tb5Ge4 may arise from the competition between the magnetic anisotropy from the spin-orbit coupling of the conduction electrons and the dipolar interactions anisotropy.

  4. 2D Tl-Pb compounds on Ge(1 1 1) surface: atomic arrangement and electronic band structure.

    Science.gov (United States)

    Gruznev, D V; Bondarenko, L V; Tupchaya, A Y; Eremeev, S V; Mihalyuk, A N; Chou, J P; Wei, C M; Zotov, A V; Saranin, A A

    2017-01-25

    Structural transformations and evolution of the electron band structure in the (Tl, Pb)/Ge(1 1 1) system have been studied using low-energy electron diffraction, scanning tunneling microscopy, angle-resolved photoelectron spectroscopy and density functional theory calculations. The two 2D Tl-Pb compounds on Ge(1 1 1), [Formula: see text]-(Tl, Pb) and [Formula: see text]-(Tl, Pb), have been found and their composition, atomic arrangement and electron properties has been characterized. The (Tl, Pb)/Ge(1 1 1)[Formula: see text] compound is almost identical to the alike (Tl, Pb)/Si(1 1 1)[Formula: see text] system from the viewpoint of its atomic structure and electronic properties. They contain 1.0 ML of Tl atoms arranged into a honeycomb network of chained trimers and 1/3 ML of Pb atoms occupying the centers of the honeycomb units. The (Tl, Pb)/Ge(1 1 1)[Formula: see text] compound contains six Tl atoms and seven Pb atoms per [Formula: see text] unit cell (i.e.  ∼0.67 ML Tl and  ∼0.78 ML Pb). Its atomic structure can be visualized as consisting of Pb hexagons surrounded by Tl trimers. The (Tl, Pb)/Ge(1 1 1)[Formula: see text] and (Tl, Pb)/Ge(1 1 1)[Formula: see text] compounds are metallic and their band structures contain spin-split surface-state bands. By analogy with the (Tl, Pb)/Si(1 1 1)[Formula: see text], these (Tl, Pb)/Ge(1 1 1) compounds are believed to be promising objects for prospective studies of superconductivity in one-atom-layer systems.

  5. 2D Tl-Pb compounds on Ge(1 1 1) surface: atomic arrangement and electronic band structure

    Science.gov (United States)

    Gruznev, D. V.; Bondarenko, L. V.; Tupchaya, A. Y.; Eremeev, S. V.; Mihalyuk, A. N.; Chou, J. P.; Wei, C. M.; Zotov, A. V.; Saranin, A. A.

    2017-01-01

    Structural transformations and evolution of the electron band structure in the (Tl, Pb)/Ge(1 1 1) system have been studied using low-energy electron diffraction, scanning tunneling microscopy, angle-resolved photoelectron spectroscopy and density functional theory calculations. The two 2D Tl-Pb compounds on Ge(1 1 1), \\sqrt{3}× \\sqrt{3} -(Tl, Pb) and 3× 3 -(Tl, Pb), have been found and their composition, atomic arrangement and electron properties has been characterized. The (Tl, Pb)/Ge(1 1 1)\\sqrt{3}× \\sqrt{3} compound is almost identical to the alike (Tl, Pb)/Si(1 1 1)\\sqrt{3}× \\sqrt{3} system from the viewpoint of its atomic structure and electronic properties. They contain 1.0 ML of Tl atoms arranged into a honeycomb network of chained trimers and 1/3 ML of Pb atoms occupying the centers of the honeycomb units. The (Tl, Pb)/Ge(1 1 1)3× 3 compound contains six Tl atoms and seven Pb atoms per 3× 3 unit cell (i.e.  ˜0.67 ML Tl and  ˜0.78 ML Pb). Its atomic structure can be visualized as consisting of Pb hexagons surrounded by Tl trimers. The (Tl, Pb)/Ge(1 1 1)\\sqrt{3}× \\sqrt{3} and (Tl, Pb)/Ge(1 1 1)3× 3 compounds are metallic and their band structures contain spin-split surface-state bands. By analogy with the (Tl, Pb)/Si(1 1 1)\\sqrt{3}× \\sqrt{3} , these (Tl, Pb)/Ge(1 1 1) compounds are believed to be promising objects for prospective studies of superconductivity in one-atom-layer systems.

  6. The effect of surface conductance on lateral gated quantum devices in Si/SiGe heterostructures

    Science.gov (United States)

    Lin, Xi; Hu, Jingshi; Lai, Andrew P.; Zhang, Zhenning; MacLean, Kenneth; Dillard, Colin; Xie, Ya-Hong; Kastner, Marc A.

    2011-07-01

    Quantum dots in Si/SiGe heterostructures are expected to have relatively long electron spin decoherence times, because of the low density of nuclear spins and the weak coupling between nuclear and electron spins. We provide experimental evidence suggesting that electron motion in a conductive layer parallel to the two-dimensional electron gas, possibly resulting from the donors used to dope the Si quantum well, is responsible for the well-known difficulty in achieving well-controlled dots in this system. Charge motion in the conductive layer can cause depletion on large length scales, making electron confinement in the dot impossible, and can give rise to noise that can overwhelm the single-electron charging signal. Results of capacitance versus gate bias measurements to characterize this conductive layer are presented.

  7. TEM studies of Ge nanocrystal formation in PECVD grown SiO{sub 2}:Ge/SiO{sub 2} multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Agan, S [Physics Department, Kirikkale University, 71450 Kirikkale (Turkey); Dana, A [Physics Department, Bilkent University, 06800 Ankara (Turkey); Aydinli, A [Physics Department, Bilkent University, 06800 Ankara (Turkey)

    2006-06-07

    We investigate the effect of annealing on the Ge nanocrystal formation in multilayered germanosilicate-oxide films grown on Si substrates by plasma enhanced chemical vapour deposition (PECVD). The multilayered samples were annealed at temperatures ranging from 750 to 900 {sup 0}C for 5 min under nitrogen atmosphere. The onset of formation of Ge nanocrystals, at 750 {sup 0}C, can be observed via high resolution TEM micrographs. The diameters of Ge nanocrystals were observed to be between 5 and 14 nm. As the annealing temperature is raised to 850 {sup 0}C, a second layer of Ge nanocrystals forms next to the original precipitation band, positioning itself closer to the substrate SiO{sub 2} interface. High resolution cross section TEM images, electron diffraction and electron energy-loss spectroscopy as well as energy-dispersive x-ray analysis (EDAX) data all indicate that Ge nanocrystals are present in each layer.

  8. Response function of semiconductor detectors, Ge and Si(Li); Funcao resposta de detectores semicondutores, Ge e Si(Li)

    Energy Technology Data Exchange (ETDEWEB)

    Zevallos Chavez, Juan Yury

    2003-07-01

    The Response Function (RF) for Ge and Si(Li) semiconductor detectors was obtained. The RF was calculated for five detectors, four Hp Ge with active volumes of 89 cm{sup 3} , 50 cm{sup 3} , 8 cm{sup 3} and 5 cm{sup 3}, and one Si(Li) with 0.143 cm{sup 3} of active volume. The interval of energy studied ranged from 6 keV up to 1.5 MeV. Two kinds of studies were done in this work. The first one was the RF dependence with the detection geometry. Here the calculation of the RF for a geometry named as simple and an extrapolation of that RF, were both done. The extrapolation process analyzed both, spectra obtained with a shielding geometry and spectra where the source-detector distance was modified. The second one was the RF dependence with the detection electronics. This study was done varying the shaping time of the pulse in the detection electronics. The purpose was to verify the effect of the ballistic deficit in the resolution of the detector. This effect was not observed. The RF components that describe the region of the total absorption of the energy of the incident photons, and the partial absorption of this energy, were both treated. In particular, empirical functions were proposed for the treatment of both, the multiple scattering originated in the detector (crystal), and the photon scattering originated in materials of the neighborhood of the crystal. Another study involving Monte Carlo simulations was also done in order to comprehend the photon scattering structures produced in an iron shield. A deconvolution method is suggested, for spectra related to scattered radiation in order to assess the dose delivered to the scatterer. (author)

  9. Research and Design of Ge0.6Si0.4/Si Strained-layer Superlattice Planar Optical Waveguide

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Calculation shows that the refraction index of Ge0.6Si0.4/Si strained-layer superlattice n≈3.64, when Lw=9nm and Lb=24nm. An algorithm of numerical iteration for effective refraction index is employed to obtain different effective refraction indexes at different thickness (L). As a result, the thickness of Ge0.6Si0.4/Si strained-layer superlattice optical waveguide, L≤363nm, can be determined, which is very important for designing waveguide devices. An optical waveguide can be made into a nanometer device by using Ge0.6Si0.4/Si strained-layer superlattice.

  10. The low temperature epitaxy of Ge on Si (1 0 0) substrate using two different precursors of GeH4 and Ge2H6

    Science.gov (United States)

    Kil, Yeon-Ho; Yuk, Sim-Hoon; Kim, Joung Hee; Kim, Taek Sung; Kim, Yong Tae; Choi, Chel-Jong; Shim, Kyu-Hwan

    2016-10-01

    We have investigated the initial stage of low temperature epitaxy (LTE) of Ge on 8″-dia. Si (1 0 0) substrate using a rapid thermal chemical vapor deposition (RTCVD) with two different precursors of GeH4 and Ge2H6. The quality of LTE Ge films such as surface morphology, defects and crystallinity were analyzed using SEM, AFM and TEM. Experimental results confirmed that the LTE Ge using Ge2H6 precursor was much more beneficial than the LTE using GeH4 in terms of growth rate (×10), stress relaxation (85% at surface), and crystal quality (low TDDs). The discrepancy looks originated from the weak Gesbnd Ge bonds requiring their dissociation energy small compared to the Gesbnd H bonds in GeH4 precursors, and the abundant supply of GeH3 molecules should stimulate chemical reactions at free surface sites. Our LTE technology would be promising for very thin Ge virtual substrate as well as be beneficial for nano-micro electronic devices in need of low temperature processes below 300-500 °C.

  11. Strain distributions and electronic property modifications in Si/Ge axial nanowire heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Swadener, John Gregory [Los Alamos National Laboratory; Picraux, Samuel T [Los Alamos National Laboratory

    2008-01-01

    Molecular dynamics simulations were carried out for Si/Ge axial nanowire heterostructures using modified effective atom method (MEAM) potentials. A Si-Ge MEAM interatomic cross potential was developed based on available experimental data and used for these studies. The atomic distortions and strain distributions near the Si/Ge interfaces are predicted for nanowires with their axes oriented along the [111] direction. The cases of 10 and 25 nm diameter SilGe biwires and of 25 nm diameter Si/Ge/Si axial heterostructures with the Ge disc 1 nm thick were studied. Substantial distortions in the height of the atoms adjacent to the interface were found for the biwires, but not for the Ge discs. Strains as high as 3.5% were found for the Ge disc and values of 2 to 2.5% were found at the Si and Ge interfacial layers in the biwires. Deformation potential theory was used to estimate the influence of the strains on the band gap, and reductions in band gap to as small as 40% of bulk values are predicted for the Ge discs. Localized regions of increased strain and resulting energy minima were also found within the Si/Ge biwire interfaces with the larger effects on the Ge side of the interface. The regions of strain maxima near and within the interfaces are anticipated to be useful for tailoring band gaps and producing quantum confinement of carriers. These results suggest nanowire heterostructures provide greater design flexibility in band structure modification than is possible with planar layer growth.

  12. Heteroepitaxial growth of Ge on compliant strained nano-structured Si lines and dots on (001) silicon on insulator substrate

    Energy Technology Data Exchange (ETDEWEB)

    Zaumseil, Peter, E-mail: zaumseil@ihp-microelectronics.com [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Yamamoto, Yuji; Schubert, Markus Andreas [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Schroeder, Thomas [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Brandenburgische Technische Universität Cottbus, Konrad-Zuse-Str.1, Cottbus, 03046 (Germany); Tillack, Bernd [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Technische Universität Berlin, HFT4, Einsteinufer 25, 10587 Berlin (Germany)

    2014-04-30

    On the way to integrate lattice mismatched semiconductors on Si(001) we studied the Ge/Si heterosystem with the aim of a misfit dislocation free deposition that offers the vision to integrate defect-free alternative semiconductor structures on Si. Periodic Ge nano-structures (dots and lines) were selectively grown by chemical vapor deposition on Si nano-islands on silicon on insulator substrate with a thin (about 10 nm) SiGe buffer layer between Si and Ge. The strain state of the structures was measured by grazing incidence and specular diffraction using laboratory-based X-ray diffraction technique. The SiGe improves the compliance of the Si compared to direct Ge deposition, prevents plastic relaxation during growth, and allows elastic relaxation before Ge is deposited on top. As a result, an epitaxial growth of Ge on Si fully free of misfit dislocations was achieved. - Highlights: • Realization of nano-structured Si islands (dots and lines) on silicon on insulator substrate • Selective Ge epitaxy on nano-structured periodic Si islands with thin SiGe buffer • Strain characterization of Ge nano-structures by X-ray diffraction • Ge heteroepitaxy on Si without misfit dislocation confirmed by transmission electron microscopy.

  13. Ultra-low Thermal Conductivity in Si/Ge Hierarchical Superlattice Nanowire.

    Science.gov (United States)

    Mu, Xin; Wang, Lili; Yang, Xueming; Zhang, Pu; To, Albert C; Luo, Tengfei

    2015-11-16

    Due to interfacial phonon scattering and nanoscale size effect, silicon/germanium (Si/Ge) superlattice nanowire (SNW) can have very low thermal conductivity, which is very attractive for thermoelectrics. In this paper, we demonstrate using molecular dynamics simulations that the already low thermal conductivity of Si/Ge SNW can be further reduced by introducing hierarchical structure to form Si/Ge hierarchical superlattice nanowire (H-SNW). The structural hierarchy introduces defects to disrupt the periodicity of regular SNW and scatters coherent phonons, which are the key contributors to thermal transport in regular SNW. Our simulation results show that periodically arranged defects in Si/Ge H-SNW lead to a ~38% reduction of the already low thermal conductivity of regular Si/Ge SNW. By randomizing the arrangement of defects and imposing additional surface complexities to enhance phonon scattering, further reduction in thermal conductivity can be achieved. Compared to pure Si nanowire, the thermal conductivity reduction of Si/Ge H-SNW can be as large as ~95%. It is concluded that the hierarchical structuring is an effective way of reducing thermal conductivity significantly in SNW, which can be a promising path for improving the efficiency of Si/Ge-based SNW thermoelectrics.

  14. Research on reverse recovery characteristics of SiGeC p-i-n diodes

    Institute of Scientific and Technical Information of China (English)

    Gao Yong; Liu Jing; Yang Yuan

    2008-01-01

    This paper analyses the reverse recovery characteristics and mechanism of SiGeC p-i-n diodes. Based on the integrated systems engineering (ISE) data, the critical physical models of SiGeC diodes are proposed. Based on heterojunction band gap engineering, the softness factor increases over six times, reverse recovery time is over 30% short and there is a 20% decrease in peak reverse recovery current for SiGeC diodes with 20% of germanium and 0.5% of carbon,compared to Si diodes. Those advantages of SiGeC p-i-n diodes are more obvious at high temperature. Compared to lifetime control, SiGeC technique is more suitable for improving diode properties and the tradeoff between reverse recovery time and forward voltage drop can be easily achieved in SiGeC diodes. Furthermore, the high thermal-stability of SiGeC diodes reduces the costs of further process steps and offers more freedoms to device design.

  15. Influence of absorber doping in a-SiC:H/a-Si:H/a-SiGe:H solar cells

    Science.gov (United States)

    Nawaz, Muhammad; Ahmad, Ashfaq

    2012-04-01

    This work deals with the design evaluation and influence of absorber doping for a-Si:H/a-SiC:H/a-SiGe:H based thin-film solar cells using a two-dimensional computer aided design (TCAD) tool. Various physical parameters of the layered structure, such as doping and thickness of the absorber layer, have been studied. For reliable device simulation with realistic predictability, the device performance is evaluated by implementing necessary models (e.g., surface recombinations, thermionic field emission tunneling model for carrier transport at the heterojunction, Schokley—Read Hall recombination model, Auger recombination model, bandgap narrowing effects, doping and temperature dependent mobility model and using Fermi—Dirac statistics). A single absorber with a graded design gives an efficiency of 10.1% for 800 nm thick multiband absorption. Similarly, a tandem design shows an efficiency of 10.4% with a total absorber of thickness of 800 nm at a bandgap of 1.75 eV and 1.0 eV for the top a-Si and bottom a-SiGe component cells. A moderate n-doping in the absorber helps to improve the efficiency while p doping in the absorber degrades efficiency due to a decrease in the VOC (and fill factor) of the device.

  16. Influence of absorber doping in a-SiC:H/a-Si:H/a-SiGe:H solar cells

    Institute of Scientific and Technical Information of China (English)

    Muhammad Nawaz; Ashfaq Ahmad

    2012-01-01

    This work deals with the design evaluation and influence of absorber doping for a-Si:H/a-SiC:H/a-SiGe:H based thin-film solar cells using a two-dimensional computer aided design (TCAD) tool.Various physical parameters of the layered structure,such as doping and thickness of the absorber layer,have been studied.For reliable device simulation with realistic predictability,the device performance is evaluated by implementing necessary models (e.g.,surface recombinations,thermionic field emission tunneling model for carrier transport at the heterojunction,Schokley-Read Hall recombination model,Auger recombination model,bandgap narrowing effects,doping and temperature dependent mobility model and using Fermi-Dirac statistics).A single absorber with a graded design gives an efficiency of 10.1% for 800 nm thick multiband absorption.Similarly,a tandem design shows an efficiency of 10.4% with a total absorber of thickness of 800 nm at a bandgap of 1.75 eV and 1.0 eV for the top a-Si and bottom a-SiGe component cells.A moderate n-doping in the absorber helps to improve the efficiency while p doping in the absorber degrades efficiency due to a decrease in the Voc (and fill factor) of the device.

  17. Secondary growth mechanism of SiGe islands deposited on a mixed-phase microcrystalline Si by ion beam co-sputtering.

    Science.gov (United States)

    Ke, S Y; Yang, J; Qiu, F; Wang, Z Q; Wang, C; Yang, Y

    2015-11-01

    We discuss the SiGe island co-sputtering deposition on a microcrystalline silicon (μc-Si) buffer layer and the secondary island growth based on this pre-SiGe island layer. The growth phenomenon of SiGe islands on crystalline silicon (c-Si) is also investigated for comparison. The pre-SiGe layer grown on μc-Si exhibits a mixed-phase structure, including SiGe islands and amorphous SiGe (a-SiGe) alloy, while the layer deposited on c-Si shows a single-phase island structure. The preferential growth and Ostwald ripening growth are shown to be the secondary growth mechanism of SiGe islands on μc-Si and c-Si, respectively. This difference may result from the effect of amorphous phase Si (AP-Si) in μc-Si on the island growth. In addition, the Si-Ge intermixing behavior of the secondary-grown islands on μc-Si is interpreted by constructing the model of lateral atomic migration, while this behavior on c-Si is ascribed to traditional uphill atomic diffusion. It is found that the aspect ratios of the preferential-grown super islands are higher than those of the Ostwald-ripening ones. The lower lateral growth rate of super islands due to the lower surface energy of AP-Si on the μc-Si buffer layer for the non-wetting of Ge at 700 °C and the stronger Si-Ge intermixing effect at 730 °C may be responsible for this aspect ratio difference.

  18. Si-Si0.7Ge0.3-Si结构的电阻特性%Resistance Characteristics of Si-Si0.7Ge0.3-Si Structure

    Institute of Scientific and Technical Information of China (English)

    王昱为; 黄非; 熊峰; 朱鹏飞; 祝昆

    2016-01-01

    Si-Si0.7Ge0.3-Si结构在激光的照射下,电阻值会随激光照射点位置的改变而改变.通过实验测量获得激光扫描Si-Si0.7Ge0.3-Si结构样品表面的二维数据分布图,并对水平方向与垂直方向进行分析,得到的电阻灵敏度最高为8.59 MΩ/mm.当激光在器件表面上的扫描线偏离X轴时,灵敏度会逐渐降低为7.72、3.98和1.50 MΩ/mm.研究表明,作为一种新型的位移传感器,Si-Si0.7Ge0.3-Si结构的电阻—位置关系曲线具有灵敏度高和线性关系好的特点.

  19. CORRIGENDUM: TEM studies of nanocrystal formation in PECVD grown for SiO2:Ge/SiO2 multilayers

    Science.gov (United States)

    Agan, S.; Dana, A.; Aydinli, A.

    2006-11-01

    In figure 4(c) the diffraction pattern of the Si substrate was inadvertently included instead of the diffraction pattern of Ge nanocrystals, and should be replaced by the new figure given (see pdf for details).

  20. Self-consistent energy balance simulations of hole dynamics in SiGe/Si THz quantum cascade structures

    Science.gov (United States)

    Ikonić, Z.; Harrison, P.; Kelsall, R. W.

    2004-12-01

    Analysis of hole transport in cascaded p-Si /SiGe quantum well structures is performed using self-consistent rate equations simulations. The hole subband structure is calculated using the 6×6k.p model, and then used to find carrier relaxation rates due to the alloy disorder, acoustic, and optical phonon scattering, as well as hole-hole scattering. The simulation accounts for the in-plane k-space anisotropy of both the hole subband structure and the scattering rates. Results are presented for prototype THzSi /SiGe quantum cascade structures.

  1. Radiation from 170 GeV electrons and positrons traversing thin Si and Ge crystals near the <110> axis

    Energy Technology Data Exchange (ETDEWEB)

    Bak, J.F.; Moeller, S.P.; Petersen, J.B.B.; Soerensen, A.H.; Uggerhoej, E.; Barberis, D.; Elsener, K.; Brodbeck, T.J.; Newton, D.; Wilson, G.W.

    1988-10-20

    The first results from a broad angular beam experiment on emission of high-energy photons from 170 GeV electrons and positrons are presented. The targets were 0.5 mm thick Si and Ge crystals. A dramatic enhancement in the emitted radiation is found for angles of incidence close to the <110> axis. The experimental results are compared to a constant-field cascade calculation.

  2. Formation and local electronic structure of Ge clusters on Si(111)-7×7 surfaces

    Institute of Scientific and Technical Information of China (English)

    Ma Hai-Feng; Xu Ming-Chun; Yang Bing; Shi Dong-Xia; Guo Hai-Ming; Pang Shi-Jin; Gao Hong-Jun

    2007-01-01

    We report the formation and local electronic structure of Ge clusters on the Si(111)-7×7 surface studied by using variable temperature scanning tunnelling microscopy (VT-STM) and low-temperature scanning tunnelling spectroscopy (STS). Atom-resolved STM images reveal that the Ge atoms are prone to forming clusters with 1.0 nm in diameter for coverage up to 0.12 ML. Such Ge clusters preferentially nucleate at the centre of the faulted-half unit cells, leading to the 'dark sites' of Si centre adatoms from the surrounding three unfaulted-half unit cells in filled-state images. Biasdependent STM images show the charge transfer from the neighbouring Si adatoms to Ge clusters. Low-temperature STS of the Ge clusters reveals that there is a band gap on the Ge cluster and the large voltage threshold is about 0.9 V.

  3. Promising features of low-temperature grown Ge nanostructures on Si(001) substrates.

    Science.gov (United States)

    Wang, Ze; Wang, Shuguang; Yin, Yefei; Liu, Tao; Lin, Dongdong; Li, De-Hui; Yang, Xinju; Jiang, Zuimin; Zhong, Zhenyang

    2017-03-17

    High-quality Ge nanostructures are obtained by molecular beam epitaxy of Ge on Si(001) substrates at 200 °C and ex situ annealing at 400 °C. Their structural properties are comprehensively characterized by atomic force microscopy, transmission electron microscopy and Raman spectroscopy. It is disclosed that they are almost defect free except for some defects at the Ge/Si interface and in the subsequent Si capping layer. The misfit strain in the nanostructure is substantially relaxed. Dramatically strong photoluminescence (PL) from the Ge nanostructures is observed. Detailed analyses on the power- and temperature-dependent PL spectra, together with a self-consistent calculation, indicate the confinement and the high quantum efficiency of excitons within the Ge nanostructures. Our results demonstrate that the Ge nanostructures obtained via the present feasible route may have great potential in optoelectronic devices for monolithic optical-electronic integration circuits.

  4. Promising features of low-temperature grown Ge nanostructures on Si(001) substrates

    Science.gov (United States)

    Wang, Ze; Wang, Shuguang; Yin, Yefei; Liu, Tao; Lin, Dongdong; Li, De-hui; Yang, Xinju; Jiang, Zuimin; Zhong, Zhenyang

    2017-03-01

    High-quality Ge nanostructures are obtained by molecular beam epitaxy of Ge on Si(001) substrates at 200 °C and ex situ annealing at 400 °C. Their structural properties are comprehensively characterized by atomic force microscopy, transmission electron microscopy and Raman spectroscopy. It is disclosed that they are almost defect free except for some defects at the Ge/Si interface and in the subsequent Si capping layer. The misfit strain in the nanostructure is substantially relaxed. Dramatically strong photoluminescence (PL) from the Ge nanostructures is observed. Detailed analyses on the power- and temperature-dependent PL spectra, together with a self-consistent calculation, indicate the confinement and the high quantum efficiency of excitons within the Ge nanostructures. Our results demonstrate that the Ge nanostructures obtained via the present feasible route may have great potential in optoelectronic devices for monolithic optical–electronic integration circuits.

  5. Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

    Science.gov (United States)

    Knapp, T. J.; Mohr, R. T.; Li, Yize Stephanie; Thorgrimsson, Brandur; Foote, Ryan H.; Wu, Xian; Ward, Daniel R.; Savage, D. E.; Lagally, M. G.; Friesen, Mark; Coppersmith, S. N.; Eriksson, M. A.

    We report the characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. Previously, all heterostructures used to form quantum dots were created using the strain-grading method of strain relaxation, a method that necessarily introduces misfit dislocations into a heterostructure and thereby degrades the reproducibility of quantum devices. Using a SiGe nanomembrane as a virtual substrate eliminates the need for misfit dislocations but requires a wet-transfer process that results in a non-epitaxial interface in close proximity to the quantum dots. We show that this interface does not prevent the formation of quantum dots, and is compatible with a tunable inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of the applied magnetic field. This work was supported in part by ARO (W911NF-12-0607), NSF (DMR-1206915, PHY-1104660), and the United States Department of Defense. The views and conclusions contained in this document are those of the author and should not be interpreted as representing the official policies, either expressly or implied, of the US Government. T.J. Knapp et al. (2015). arXiv:1510.08888 [cond-mat.mes-hall].

  6. Diffusion Mechanisms and Lattice Locations of Thermal-Equilibrium Defects in Si-Ge Alloys

    CERN Multimedia

    Lyutovich, K; Touboltsev, V; Laitinen, P O; Strohm, A

    2002-01-01

    It is generally accepted that Ge and Si differ considerably with respect to intrinsic-point-defect-mediated diffusion. In Ge, the native point defects dominating under thermal-equilibium conditions at all solid-state temperatures accessible in diffusion experiments are vacancies, and therefore Ge self-diffusion is vacancy-controlled. In Si, by contrast, self-interstitials and vacancies co-exist in thermal equilibrium. Whereas in the most thoroughly investigated temperature regime above about 1000$^\\circ$C Si self-diffusion is self-interstitial-controlled, it is vacancy-controlled at lower temperatures. According to the scenario displayed above, self-diffusion in Si-Ge alloys is expected to change from an interstitialcy mechanism on the Si side to a vacancy mechanism on the Ge side. Therefore, $^{71}$Ge self-diffusion experiments in Si$_{1- \\it y}$Ge$_{\\it y}$ as a function of composition Y are highly interesting. In a first series of experiments the diffusion of Ge in 0.4 to 10 $\\mu$m thick, relaxed, low-disl...

  7. Long-Term Reliability of High Speed SiGe/Si Heterojunction Bipolar Transistors

    Science.gov (United States)

    Ponchak, George E. (Technical Monitor); Bhattacharya, Pallab

    2003-01-01

    Accelerated lifetime tests were performed on double-mesa structure Si/Si0.7Ge0.3/Si npn heterojunction bipolar transistors, grown by molecular beam epitaxy, in the temperature range of 175C-275C. Both single- and multiple finger transistors were tested. The single-finger transistors (with 5x20 micron sq m emitter area) have DC current gains approximately 40-50 and f(sub T) and f(sub MAX) of up to 22 GHz and 25 GHz, respectively. The multiple finger transistors (1.4 micron finger width, 9 emitter fingers with total emitter area of 403 micron sq m) have similar DC current gain but f(sub T) of 50 GHz. It is found that a gradual degradation in these devices is caused by the recombination enhanced impurity diffusion (REID) of boron atoms from the p-type base region and the associated formation of parasitic energy barriers to electron transport from the emitter to collector layers. This REID has been quantitatively modeled and explained, to the first order of approximation, and the agreement with the measured data is good. The mean time to failure (MTTF) of the devices at room temperature is estimated from the extrapolation of the Arrhenius plots of device lifetime versus reciprocal temperature. The results of the reliability tests offer valuable feedback for SiGe heterostructure design in order to improve the long-term reliability of the devices and circuits made with them. Hot electron induced degradation of the base-emitter junction was also observed during the accelerated lifetime testing. In order to improve the HBT reliability endangered by the hot electrons, deuterium sintered techniques have been proposed. The preliminary results from this study show that a deuterium-sintered HBT is, indeed, more resistant to hot-electron induced base-emitter junction degradation. SiGe/Si based amplifier circuits were also subjected to lifetime testing and we extrapolate MTTF is approximately 1.1_10(exp 6) hours at 125iC junction temperature from the circuit lifetime data.

  8. Si/Ge photodiodes for coherent and analog communication

    Science.gov (United States)

    Piels, Molly

    allows optimization of the absorption profile independently from the RC-limited frequency response and compression current and ultimately enables larger saturation current-bandwidth products. This thesis includes the first theory, fabrication, and measurement of a uni-traveling carrier photodiode on the Si/Ge platform. Key contributions include an accurate nonlinear device model and a complete set of processes and design rules for fabricating Ge devices in the UCSB nanofab. The UTC structure is shown to be useful in extending the bandwidth and power handling capabilities of waveguide-integrated photodiodes, especially at high frequencies.

  9. Thermal transport in nanocrystalline Si and SiGe by ab initio based Monte Carlo simulation.

    Science.gov (United States)

    Yang, Lina; Minnich, Austin J

    2017-03-14

    Nanocrystalline thermoelectric materials based on Si have long been of interest because Si is earth-abundant, inexpensive, and non-toxic. However, a poor understanding of phonon grain boundary scattering and its effect on thermal conductivity has impeded efforts to improve the thermoelectric figure of merit. Here, we report an ab-initio based computational study of thermal transport in nanocrystalline Si-based materials using a variance-reduced Monte Carlo method with the full phonon dispersion and intrinsic lifetimes from first-principles as input. By fitting the transmission profile of grain boundaries, we obtain excellent agreement with experimental thermal conductivity of nanocrystalline Si [Wang et al. Nano Letters 11, 2206 (2011)]. Based on these calculations, we examine phonon transport in nanocrystalline SiGe alloys with ab-initio electron-phonon scattering rates. Our calculations show that low energy phonons still transport substantial amounts of heat in these materials, despite scattering by electron-phonon interactions, due to the high transmission of phonons at grain boundaries, and thus improvements in ZT are still possible by disrupting these modes. This work demonstrates the important insights into phonon transport that can be obtained using ab-initio based Monte Carlo simulations in complex nanostructured materials.

  10. Original Ge-induced phenomena on various SiC(0 0 0 1) reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Ait-Mansour, K [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Dentel, D [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Kubler, L [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Diani, M [LSGM, Departement de Physique, Faculte des Sciences et Techniques, Tanger BP 416 (Morocco); Derivaz, M [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Bischoff, J L [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France)

    2007-10-21

    Using complementary surface analysis techniques, we study the Ge growth on distinct SiC(0 0 0 1) reconstructions and elucidate complex mechanisms occurring by thermal activation. Two Si-rich reconstructions (3 x 3) and ({radical}3 x {radical}3)R30{sup 0}({radical}3), and one C-rich, (6{radical}3 x 6{radical}3)R30{sup 0}(6{radical}3), are concerned, on which Ge is found to grow in Stranski-Krastanov and Volmer-Weber modes, respectively. The best Ge-wetting layer is favoured on the {radical}3 (less Si-rich) because closest to a perfect truncated SiC(0 0 0 1) termination. At sufficiently high temperature, the Ge-wetting layer is organized in the form of a (4 x 4)Ge reconstruction for which we propose a first atomic model that is based on the 3 x 3 structure. Annealing Ge on the (3 x 3) and 6{radical}3 surfaces provokes spectacular successive 2D/3D and unusual 3D/2D transitions not only of Ge but also of Si and C, respectively, coming from the surface initial richness. In both cases, a phase separation is observed either in the 2D or 3D structures, which is unexpected for the Ge/Si binary system and somewhat usual for the Ge/C one. In the case of Ge on 6{radical}3, a special 2D heterostructure graphite/Ge/SiC is achieved at the atomic level. This acts as a Schottky barrier and then can be promising for future possible applications. (review article)

  11. Growth and characterization of gold catalyzed SiGe nanowires and alternative metal-catalyzed Si nanowires

    Directory of Open Access Journals (Sweden)

    Gentile Pascal

    2011-01-01

    Full Text Available Abstract The growth of semiconductor (SC nanowires (NW by CVD using Au-catalyzed VLS process has been widely studied over the past few years. Among others SC, it is possible to grow pure Si or SiGe NW thanks to these techniques. Nevertheless, Au could deteriorate the electric properties of SC and the use of other metal catalysts will be mandatory if NW are to be designed for innovating electronic. First, this article's focus will be on SiGe NW's growth using Au catalyst. The authors managed to grow SiGe NW between 350 and 400°C. Ge concentration (x in Si1- x Ge x NW has been successfully varied by modifying the gas flow ratio: R = GeH4/(SiH4 + GeH4. Characterization (by Raman spectroscopy and XRD revealed concentrations varying from 0.2 to 0.46 on NW grown at 375°C, with R varying from 0.05 to 0.15. Second, the results of Si NW growths by CVD using alternatives catalysts such as platinum-, palladium- and nickel-silicides are presented. This study, carried out on a LPCVD furnace, aimed at defining Si NW growth conditions when using such catalysts. Since the growth temperatures investigated are lower than the eutectic temperatures of these Si-metal alloys, VSS growth is expected and observed. Different temperatures and HCl flow rates have been tested with the aim of minimizing 2D growth which induces an important tapering of the NW. Finally, mechanical characterization of single NW has been carried out using an AFM method developed at the LTM. It consists in measuring the deflection of an AFM tip while performing approach-retract curves at various positions along the length of a cantilevered NW. This approach allows the measurement of as-grown single NW's Young modulus and spring constant, and alleviates uncertainties inherent in single point measurement.

  12. Contribution à la cristallochimie des isotypes de ThCr 2Si 2 et CaBe 2Ge 2. I. Les systèmes La T2- xT' xGe 2 ( T, T' = Ru, Rh, Pd, Ir, Pt) et La 1- xCa xCa xIr 2Ge 2: Distribution des éléments de transition dans le type CaBe 2Ge 2

    Science.gov (United States)

    Venturini, G.; Malaman, B.; Roques, B.

    1989-03-01

    There are several singularities in the systems investigated. Although the three germanides La T2Ge 2( T = Ru, Rh, Pd) are isostructural with ThCr 2Si 2, a complete solid solution occurs only between LaRu 2Ge 2 and LaRh 2Ge 2; in the system LaRh 2Ge 2LaPd 2Ge 2, there is a range of CaBe 2Ge 2-type solid solutions. The lattice constants of the ThCr 2Si 2-type compounds vary curiously according to the valence electron concentration (VEC). The CaBe 2Ge 2-type germanides are confined in a narrow range of VEC. The new compound CaIr 2Ge 2 is then of the ThCr 2Si 2-type while LaIr 2Ge 2 is of the CaBe 2Ge 2-type. In the latter structural type, the square pyramids of Ge atoms are favorite sites for Ir or Pt atoms. These results are discussed.

  13. Energy band design for p-type tensile strained Si/SiGe multi-quantum well infrared photodetector

    Institute of Scientific and Technical Information of China (English)

    LI Jin-tao; CHEN Song-yan; QI Dong-feng; HUANG Wei; LI Cheng; LAI Hong-kai

    2011-01-01

    The band structure of the confined states is calculated for Si/SiGe multi-quantum well infrared photodetector (M-QWIP). The influence of the Ge component in pseudosubstrate on the energy band structure of Si/Si0.54Ce0.46 multi-quantum wells (MQWs) is investigated. It is found that the high energy levels in the MQWs move up while the low energy levels move down as the Ge component in psendosubstrate increases. The influence of the barrier width on the energy band structure of MQWs is also studied based on the 6 × 6 k-p method. The results show that the Si barrier between 5 nm and 10 nm is optimized to enhance the intersubband absorption in the MQWs.

  14. Formation of uniform high-density and small-size Ge/Si quantum dots by scanning pulsed laser annealing of pre-deposited Ge/Si film

    Directory of Open Access Journals (Sweden)

    Hamza Qayyum

    2016-05-01

    Full Text Available The capability to fabricate Ge/Si quantum dots with small dot size and high dot density uniformly over a large area is crucial for many applications. In this work, we demonstrate that this can be achieved by scanning a pre-deposited Ge thin layer on Si substrate with a line-focused pulsed laser beam to induce formation of quantum dots. With suitable setting, Ge/Si quantum dots with a mean height of 2.9 nm, a mean diameter of 25 nm, and a dot density of 6×1010 cm−2 could be formed over an area larger than 4 mm2. The average size of the laser-induced quantum dots is smaller while their density is higher than that of quantum dots grown by using Stranski-Krastanov growth mode. Based on the dependence of the characteristics of quantum dots on the laser parameters, a model consisting of laser-induced strain, surface diffusion, and Ostwald ripening is proposed for the mechanism underlying the formation of the Ge/Si quantum dots. The technique demonstrated could be applicable to other materials besides Ge/Si.

  15. TEM study on Si0.65Ge0.35/p-Si HIP infrared detector

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Microstructure of P+ -Si0.65Ge0.35/p-Si HIP infrared detector has been studied by using localization cross-section transmission electron microscopy. The photosensitive region of the detector consists of 6 P+ -Si0.65Ge0.35 layers and 5 UD-Si layers, whichare flat and have thickness of 6 nm and 32 nm, respectively. A stress field exists on the interface between Si0.65Ge0.35 and UD-Si layers, but no any crystal defect has been found in this region, except the edges of this region. Both Si0.65Ge0.35 and UD-Si layers on amorphous SiO2 layer consist of polycrystals and are in wave. There is defect area in the edges of photosensitive region.The area appears in a shape of inverse triangle and the maximum width is less than 120 nm. The crystal defects are stacking faults and microtwins.

  16. Microwave based nanogenerator using the ratchet effect in Si/SiGe heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Bisotto, I; Kannan, E S; Sassine, S; Portal, J-C [LNCMI, UPR 3228, CNRS-INSA-UJF-UPS, BP 166, 38042 Grenoble, Cedex 9 (France); Murali, R; Beck, T J [Microelectronics Research Center Georgia Institute of Technology, 791 Atlantic Drive NW, Atlanta, GA 30332 (United States); Jalabert, L [LIMMS/CNRS-IIS, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, 153-8505, Tokyo (Japan)

    2011-06-17

    Ratchet based microwave current generators and detectors were developed in Si/SiGe heterostructures for wireless communication with the possibility of extending the detection limit to the terahertz range. A microwave induced ratchet current was generated in the two-dimensional electron gas by patterning an array of semicircular antidots in hexagonal geometry. The spatial asymmetry created by the semicircular antidots forces the electrons under the influence of the microwave electric field to move preferentially towards the direction of the semidisc axis. A photovoltage of the order of few millivolts was observed. Such a photovoltage was completely absent in a symmetric system consisting of circular antidots. The induced photovoltage increased monotonically with microwave power and was found to be independent of the microwave polarization. This device opens the possibility of employing silicon based heterostructures for nanogenerators and other wireless communication devices using microwaves.

  17. Observation of ballistic conductance and Aharonov-Bohm oscillations in Si/SiGe heterostructures

    Science.gov (United States)

    Gao, W. X.; Ismail, K.; Lee, K. Y.; Chu, J. O.; Washburn, S.

    1994-12-01

    We have fabricated quantum devices from remotely doped Si/SiGe heterostructures. The devices are interferometers (loops) similar in plan to those used in experiments on ballistic GaAs/AlxGa1-xAs devices. The loops are approximately 2r=0.8 μm in diameter with linewidths of w=0.4 μm. We have observed clear Aharonov-Bohm (AB) oscillations that vanish systematically as the carrier temperature increases. Response of up to the second harmonic of the fundamental AB frequency e/h implies a phase coherence length of around Lφ=1.2 μm. In some samples, we see steps in conductance G(Vg) as a function of gate voltage similar to the ballistic mode steps seen in GaAs/AlxGa1-xAs point contacts.

  18. Electron transport in n-doped Si/SiGe quantum cascade structures

    Science.gov (United States)

    Lazic, I.; Ikonic, Z.; Milanovic, V.; Kelsall, R. W.; Indjin, D.; Harrison, P.

    2007-05-01

    An electron transport model in n-Si/SiGe quantum cascade or superlattice structures is described. The model uses the electronic structure calculated within the effective-mass complex-energy framework, separately for perpendicular (Xz) and in-plane (Xxy) valleys, the degeneracy of which is lifted by strain, and additionally by size quantization. The transport is then described via scattering between quantized states, using a rate equations approach and tight-binding expansion, taking the coupling with two nearest-neighbor periods. Acoustic phonon, optical phonon, alloy disorder, and interface roughness scattering are taken into account. The calculated current/voltage dependence and gain profiles are presented for two simple superlattice structures.

  19. n-Si/SiGe quantum cascade structures for THz emission

    Energy Technology Data Exchange (ETDEWEB)

    Ikonic, Z. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom)]. E-mail: z.ikonic@ee.leeds.ac.uk; Lazic, I. [School of Electrical Engineering, University of Belgrade, Belgrade (Yugoslavia); Department of Materials Science, Delft University of Technology, 2628 AL Delft (Netherlands); Milanovic, V. [School of Electrical Engineering, University of Belgrade, Belgrade (Yugoslavia); Kelsall, R.W. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Indjin, D. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Harrison, P. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom)

    2006-12-15

    In this work we report on modeling the electron transport in n-Si/SiGe structures. The electronic structure is calculated within the effective-mass complex-energy framework, separately for perpendicular (X {sub z} ) and in-plane (X {sub xy} ) valleys, the degeneracy of which is lifted by strain, and additionally by size quantization. The transport is described via scattering between quantized states, using the rate equations approach and tight-binding expansion, taking the coupling with two nearest-neighbour periods. The acoustic phonon, optical phonon, alloy and interface roughness scattering are taken in the model. The calculated U/I dependence and gain profiles are presented for a couple of QC structures.

  20. Numerical simulation of strained Si/SiGe devices: the hierarchical approach

    Science.gov (United States)

    Meinerzhagen, B.; Jungemann, C.; Neinhüs, B.; Bartels, M.

    2004-03-01

    Performance predictions for 25 nm strained Si CMOS devices which are based on full-band Monte Carlo (FBMC) device simulations and which are in good agreement with the most recent experimental trends are presented. The FBMC simulator itself is part of a hierarchical device simulation system which allows to perform time-efficient hierarchical hydrodynamic (HD) device simulations of modern SiGe HBTs. As demonstrated below, the accuracy of a such a hydrodynamic-based dc, ac, transient, and noise analysis is comparable to FBMC device simulations. In addition, the new hierarchical numerical noise simulation method is experimentally verified based on a modern rf-CMOS technology of Philips Research. The MC-enhanced simulation accuracy of the hierarchical hydrodynamic and drift diffusion (DD) models can be also exploited for mixed-mode circuit simulations, which is shown by typical power sweep simulations of an industrial rf power amplifier.

  1. Strain fields and chemical composition maps of Si Ge:Si(001) quantum dot molecules

    Energy Technology Data Exchange (ETDEWEB)

    Leite, Marina Soares; Medeiros-Ribeiro, Gilberto [Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas, SP (Brazil); Gray, Jeniffer L.; Hull, Robert [University of Virginia, Charlottesville, VA (United States); Floro, Jerrold A. [Sandia National Laboratories, NM (United States); Magalhaes-Paniago, Rogerio [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Fisica

    2006-07-01

    Depending on kinetic and thermodynamic factors, numerous interesting structures can be created starting from epitaxially grown Si Ge:Si(001). In a regime of relatively low growth temperatures (about 550 degree C), a cooperative nucleation process takes place: pyramidal pits are formed preferentially, followed by the nucleation of {l_brace}105{r_brace} elongated islands, leading to Quantum Dot Molecules (QDMs), where the islands can interact electronically with each other. A thorough understanding of the formation of these structures requires knowledge of their strain and compositional fields. Recently, Grazing Incidence Anomalous X ray Diffraction (GIXRD) has been used to understand these issues. The purpose of the measurements taken on the XD1 beam line of the LNLS was to investigate compositional inhomogeneities in QDMs, which helped to elucidate their mechanisms of formation. (author)

  2. Conversion Matrix Analysis of SiGe HBT Gilbert Cell Mixers

    DEFF Research Database (Denmark)

    Johansen, Tom Keinicke; Vidkjær, Jens; Krozer, Viktor

    2004-01-01

    The frequency response of SiGe HBT active mixers based on the Gilbert cell topology is analyzed theoretically. The time-varying operation of the Gilbert cell mixer is taken into account by applying conversion matrix analysis. The main bandwidth limiting mechanisms experienced in SiGe HBT Gilbert...... cell mixers performing frequency conversion of ultra-wideband signals is discussed. The analysis is verified by computer simulations using a realistic high-frequency large-signal SiGe HBT model. Design optimization steps towards ultra-wideband operation for Gilbert cell mixers is discussed....

  3. Radiation damage of SiGe HBT Technologies at different bias configurations

    CERN Document Server

    Ullán, M; Lozano, M; Pellegrini, G; Knoll, D; Heinemann, B

    2008-01-01

    SiGe BiCMOS technologies are being proposed for the Front-end readout of the detectors in the middle region of the ATLAS-Upgrade. The radiation hardness of the SiGe bipolar transistors is being assessed for this application through irradiations with different particles. Biasing conditions during irradiation of bipolar transistors or circuits have an influence on the damage and there is a risk of erroneous results. We have performed several irradiation experiments of SiGe devices from IHP in different bias conditions. We have observed a systematic trend in gamma irradiations, showing a smaller damage in transistors irradiated biased compared to shorted or floating terminals.

  4. New Photoluminescence Phenomena of Ge/SiO2 Glass Synthesized by Sol-gel Method

    Institute of Scientific and Technical Information of China (English)

    Yu Ying FENG; Xiao Tian GU; Jia Hong ZHOU; Jian Chun BAO; Gang LI; Tian Hong LU

    2004-01-01

    New Ge/SiO2 glasses have been synthesized by heating the GeO2/SiO2 dry gels under H2 gas at 700℃. The resulting fluorescence spectra show that this kind of Ge/SiO2 glasses emit strong photoluminescence at 392 nm (3.12 eV), medium strong photoluminescence at 600 nm (2.05 eV)and weak photoluminescence at 770 nm (1.60 eV) respectively. Possible photolnminescence mechanisms are also discussed based on the results of X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS).

  5. Investigation of Defect Free SiGe Nanowire Biosensor Modified by Dual Plasma Technology.

    Science.gov (United States)

    Chen, Yi-Ming; Chang, Tai-Yuan; Lai, Chiung-Hui; Chang, Kow-Ming; Chen, Chu-Feng; Lai, Yi-Lung; Whang, Allen Jong-Woei; Lai, Hui-Lung; Hsu, Terng-Ren

    2016-02-01

    Semiconductor nanowires (NWs) have been extensively investigated and discussed in various fields due to their unique physical properties. In this paper, we successfully produce SiGe NWs biosensor by VLSI technology. We propose the dual plasma technology with CF4 plasma pre-treatment and N2 plasma post-treatment for repairs of defects as well as optimization of SiGe NWs biosensor. The results indicate that sensitivity (S) of the biosensor with dual plasma technology has significantly improved at least 32.8%, suitable for producing industrial SiGe NWs biosensor in the future.

  6. Effect of Fe substitution on the structure and magnetocaloric effect of Mn5-xFexGeSi2 alloys

    Science.gov (United States)

    Sun, Y. W.; Yan, J. L.; Feng, E. L.; Tang, G. W.; Zhou, K. W.

    2017-01-01

    The structure and magnetocaloric effect of Mn5-xFexGeSi2 compounds were studied. Analysis of X-ray powder diffraction and energy dispersive X-Ray spectroscopy revealed that Mn5-xFexGeSi2 alloys with x<1 crystallize in the Mn5Si3-type structure (space group P63/mcm), maintaining the structure of Mn5Ge3; and alloys with x=1.5 and 2 consist of the major Mn5Si3-type phase and the minor Ni2In-type phase (space group P63/mmc). The results of Rietveld refinement showed that the cell parameters for the Mn5Si3-type phase decrease with increasing Fe content. The positive slopes in Arrott plots indicate that a second-order ferromagnetic to paramagnetic transition occurs. The Curie temperature increases with increasing Fe content from 182 K for x=0.6 to 224 K for x=2. The maximum magnetic entropy change of 3.7 J/(kg K) for x=0.8 was found under a magnetic field change of 0-20 kOe.

  7. Sidewall damage in plasma etching of Si/SiGe heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ding, R.; Klein, L. J.; Friesen, Mark G.; Eriksson, M. A.; Wendt, A. E. [Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); IBM TJ Watson Research Center, Yorktown Heights, New York 10598 (United States); Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2009-07-15

    Plasma etching is a critical tool in the fabrication of Si/SiGe heterostructure quantum devices, but it also presents challenges, including damage to etched feature sidewalls that affects device performance. Chemical and structural changes in device feature sidewalls associated with plasma-surface interactions are considered damage, as they affect band structure and electrical conduction in the active region of the device. Here the authors report the results of experiments designed to better understand the mechanisms of plasma-induced sidewall damage in modulation-doped Si/SiGe heterostructures containing a two-dimensional electron gas. Damage to straight wires fabricated in the heterostructure using plasma etching was characterized both by measuring the width of the nonconductive ''sidewall depletion'' region at the device sidewall and by measuring the noise level factor {gamma}{sub H}/N determined from spectra of the low frequency noise. Observed increases in sidewall depletion width with increasing etch depth are tentatively attributed to the increase in total number of sidewall defects with increased plasma exposure time. Excess negative charge trapped on the feature sidewall could be another contributing factor. Defects at the bottom of etched features appear to contribute minimally. The noise level shows a minimum at an ion bombardment energy of {approx}100 eV, while the sidewall depletion width is independent of bias voltage, within experimental uncertainty. A proposed explanation of the noise trend involves two competing effects as ion energy increases: the increase in damage caused by each bombarding ion and the reduction in total number of incident ions due to shorter etch times.

  8. Hole emission mechanism in Ge/Si quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Kaniewska, M.; Zaremba, G.; Kaczmarczyk, M.; Wzorek, M.; Czerwinski, A. [Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Engstroem, O. [Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Chalmers University of Technology, Kemivaegen 9, 412 96 Goeteborg (Sweden); Karmous, A.; Kirfel, O.; Kasper, E. [Institute for Semiconductor Engineering, University of Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart (Germany); Raeissi, B.; Piscator, J. [Chalmers University of Technology, Kemivaegen 9, 412 96 Goeteborg (Sweden); Surma, B.; Wnuk, A. [Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland)

    2011-02-15

    The mechanisms determining emission of holes in self-assembled Ge quantum dots (QDs) embedded in the p-type Si matrix have been investigated. Specimens were prepared by molecular beam epitaxy (MBE). Electrical methods such as deep level transient spectroscopy (DLTS) and capacitance versus voltage (C-V) measurements were used for the study. The emission mechanisms were identified by measuring a QD-related signal as a function of the repetition frequency of the filling pulses with the reverse voltage and the pulse voltage as a parameter. An observed shift of the signal position or its absence versus the voltage parameters was interpreted in terms of thermal, tunnelling and mixed processes and attributed to the presence of a Coulomb barrier formed as a result of the charging effect. Thermal emission properties of the QDs were characterized under such measurement conditions that tunnelling contributions to the DLTS spectra could be neglected (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Polycrystalline GeSn thin films on Si formed by alloy evaporation

    Science.gov (United States)

    Kim, Munho; Fan, Wenjuan; Seo, Jung-Hun; Cho, Namki; Liu, Shih-Chia; Geng, Dalong; Liu, Yonghao; Gong, Shaoqin; Wang, Xudong; Zhou, Weidong; Ma, Zhenqiang

    2015-06-01

    Polycrystalline GeSn thin films on Si substrates with a Sn composition up to 4.5% have been fabricated and characterized. The crystalline structure, surface morphology, and infrared (IR) absorption coefficient of the annealed GeSn thin films were carefully investigated. It was found that the GeSn thin films with a Sn composition of 4.5% annealed at 450 °C possessed a desirable polycrystalline structure according to X-ray diffraction (XRD) analyses and Raman spectroscopy analyses. In addition, the absorption coefficient of the polycrystalline GeSn thin films in the IR region was significantly better than that of the single crystalline bulk Ge.

  10. Restrictions of Si-based Ge nanodots from porous alumina membranes

    Science.gov (United States)

    Zhan, Wenbo; Huangfu, Yourui; Ding, Guqiao; Ye, Hui

    2013-08-01

    This paper reports growth of ordered Ge nanodots (NDs) with uniform sizes on silicon substrates using porous alumina membranes (PAMs) as templates. The relationships between substrate temperatures (400-600 °C) and site distribution of Ge NDs are studied. Ordered arrangements of Ge NDs are realized at 400 °C and 500 °C, respectively. Due to joint effect of substrate temperature and restrictions from PAM, an uncommon size change trend is found. At 400 °C, triangular pyramid-like and short cylindrical Ge NDs are obtained with different nanopore aspect ratios of PAMs. A geometrical optic method is used to analyze the mechanism of Ge NDs with such shapes. Raman characterization is utilized to study the strain in Ge NDs. As a result, almost pure Ge content and 1.5% tensile strain are revealed, which are attributed respectively to the low substrate temperature and thermal mismatch among Si substrate, Ge ND and PAM.

  11. Influence of Ce-H bonding on the physical properties of the hydrides CeCoSiH(1.0) and CeCoGeH(1.0).

    Science.gov (United States)

    Chevalier, B; Matar, S F; Ménétrier, M; Marcos, J Sanchez; Fernandez, J Rodriguez

    2006-07-05

    The hydrides CeCoSiH(1.0) and CeCoGeH(1.0) which crystallize like the parent antiferromagnetic compounds CeCoSi and CeCoGe in the tetragonal CeFeSi-type structure, have been investigated by specific heat and thermoelectric power measurements and (1)H nuclear magnetic resonance (NMR). CeCoSiH(1.0) is an intermediate valence compound whereas CeCoGeH(1.0) can be considered as a nearly trivalent cerium compound. This behaviour is corroborated by the occurrence of a slight broadening of the (1)H NMR signal in the sequence [Formula: see text]. The band structure calculations performed on these hydrides reveal the existence of strong bonding Ce-H interaction, found to be larger in CeCoSiH(1.0) than in CeCoGeH(1.0).

  12. Low Temperature Rhombohedral Single Crystal SiGe Epitaxy on c-plane Sapphire

    Science.gov (United States)

    Duzik, Adam J.; Choi, Sang H.

    2016-01-01

    Current best practice in epitaxial growth of rhombohedral SiGe onto (0001) sapphire (Al2O3) substrate surfaces requires extreme conditions to grow a single crystal SiGe film. Previous models described the sapphire surface reconstruction as the overriding factor in rhombohedral epitaxy, requiring a high temperature Al-terminated surface for high quality films. Temperatures in the 850-1100 C range were thought to be necessary to get SiGe to form coherent atomic matching between the (111) SiGe plane and the (0001) sapphire surface. Such fabrication conditions are difficult and uneconomical, hindering widespread application. This work proposes an alternative model that considers the bulk sapphire structure and determines how the SiGe film nucleates and grows. Accounting for thermal expansion effects, calculations using this new model show that both pure Ge and SiGe can form single crystal films in the 450-550 C temperature range. Experimental results confirm these predictions, where x-ray diffraction and atomic force microscopy show the films fabricated at low temperature rival the high temperature films in crystallographic and surface quality. Finally, an explanation is provided for why films of comparable high quality can be produced in either temperature range.

  13. Matrix effects in SIMS depth profiles of SiGe relaxed buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Almazan, F.; Napolitani, E.; Carnera, A.; Drigo, A.V.; Isella, G.; Kaenel, H. von; Berti, M

    2004-06-15

    The combined use of Rutherford backscattering spectrometry and secondary ion mass spectroscopy allowed a complete characterization of a set of SiGe relaxed buffer layers grown by low-energy plasma-enhanced chemical vapor deposition. The Ge contents for the top SiGe constant composition layers have been obtained by RBS. Matrix effects have been studied by using monoatomic and biatomic ions as well as low and high energy O{sub 2}{sup +} and Cs{sup +} primary beam ions. We show that matrix effects are suppressed when an O{sub 2}{sup +} primary beam ion source is used at 3 keV, and when detecting with {sup 30}Si{sup +} and {sup 70}Ge{sup +} secondary ions for Ge contents <0.47. For higher Ge contents a better compromise is achieved with Cs{sup +} bombardment at 14.5 keV when detecting with {sup 74}Ge{sup 76}Ge{sup -} secondary ions. The procedure allows to extract the Ge concentration profiles with good accuracy even at very high depths and at very low Ge concentrations.

  14. Fabrication and Microstructure of SiO2-GeO2 Sol-gel Glass Coatings

    Institute of Scientific and Technical Information of China (English)

    JING Cheng-bin; ZHAO Xiu-jian; TAO Hai-zhen; Wang Xi-na; LIU Ai-yun

    2003-01-01

    SiO2-GeO2 sols and gel glass coatings with different contents of germanium dioxide were fabricated.Stable and transparent sols could only be obtained when the content of GeO2 was under 35%.It is shown by SEM that only one continuous phase is observed in the coating of 65SiO2·35GeO2 and plenty of Ge,O and Si were all found in it.However,the separated phase is found in the coating of 60SiO2·40GeO2 and a large number of Ge and O.It is proved by the Raman scattering investigation that the separated phase in the coating of 60SiO2·40GeO2 is germanium dioxide.The congeries of hydrolystates of Cl3GeCH2CH2COOH play the main role in the formation of the separated phase when the proportion of GeO2 is much higher.Si-O-Ge,Si-O-Si,and Ge-O-Ge bonds form in the coating of 65SiO2·35GeO2 and this coating is homogenous.

  15. Gettering effects in Si{sub x}Ge{sub 1-x} single crystalline wafers

    Energy Technology Data Exchange (ETDEWEB)

    Wollweber, J.; Schulz, D.; Schroeder, W. [Institut fuer Kristallzuechtung, Berlin (Germany)] [and others

    1995-08-01

    The new interest in single crystal growth of SiGe solid solutions is caused by the development of advanced electronics. The SiGe alloys are mostly used in the form of Si/Si{sub x}Ge{sub 1-x} epitaxial layers in heterostructures, the perfect bulk crystals are required to study fundamental properties. Furthermore, Si{sub x}Ge{sub 1-x} crystals can be used as a substrate material instead of Silicon in order to avoid the buffer layers between the Silicon substrate and strained Si{sub x}Ge{sub 1-x}. Monocrystalline SiGe alloys may be a potential candidate as a base material for infrared solar cells too because of an enhanced IR-sensitivity. In this paper we report a new approach to the growth of Si{sub x}Ge{sub 1-x} single crystals (up to 2{double_prime} in diameter) using the crucible free rf-heated float zone technique as well as the Czochralski-technique for solar cells. The goal is to produce solar cells with an increased photo current in comparison to Silicon cells. based on the lower bandgap of the alloyed crystal. In order to be able to use the Si cells technology (a matter still pending to be proven), low contents of Ge are intended, desirably in the range of about x=0.2. It is worth to mention, that in the conventional Silicon cell processes which give efficiencies up to 18-19%, this efficiency is not limited by the bulk base recombination in the lifetime is above 200 {mu}s there. We can conclude, that there is no basic limitation did prevents Si{sub x}Ge{sub 1-x} wafers to present high lifetimes, above 200{mu}s, at least if the Ge content is below 5%. We can also conclude that the phosphorous gettering from a POCl{sub 3} source, used in silicon, can be successfully used to enhance lifetimes in Si{sub x}Ge{sub 1-x}, at least for the Ge concentration used here.

  16. Buffer-Free GeSn and SiGeSn Growth on Si Substrate Using In Situ SnD4 Gas Mixing

    Science.gov (United States)

    Mosleh, Aboozar; Alher, Murtadha; Cousar, Larry C.; Du, Wei; Ghetmiri, Seyed Amir; Al-Kabi, Sattar; Dou, Wei; Grant, Perry C.; Sun, Greg; Soref, Richard A.; Li, Baohua; Naseem, Hameed A.; Yu, Shui-Qing

    2016-04-01

    Buffer-free GeSn and SiGeSn films have been deposited on Si via a cold-wall, ultra-high vacuum chemical vapor deposition reactor using in situ gas mixing of deuterated stannane, silane and germane. Material characterization of the films using x-ray diffraction and transmission electron microscopy shows crystalline growth with an array of misfit dislocation formed at the Si substrate interface. Energy dispersive x-ray maps attained from the samples show uniform incorporation of the elements. The Z-contrast map of the high-angle annular dark-field of the film cross section shows uniform incorporation along the growth as well. Optical characterization of the GeSn films through photoluminescence technique shows reduction in the bandgap edge of the materials.

  17. Luminescence of Strain Compensated Si/Si0.62 Ge0.38 Quantum Well Grown on Si0.75 Ge0.25 Virtual Substrate%Si0.75Ge0.25虚衬底上应变补偿Si/Si0.61Ge0.38量子阱发光

    Institute of Scientific and Technical Information of China (English)

    廖凌宏; 周志文; 李成; 陈松岩; 赖虹凯; 余金中; 王启明

    2009-01-01

    由于Si/SiGe异质结构的带阶差主要发生在价带,为实现高效率的发光,本文从理论上设计了在硅基Si1-x Gex虚衬底上外延应变补偿的Si/S1-y Ge,(y>x)量子阱的能带结构,将量子阱对电子的限制势垒提高到100meV以上.在实验上,采用300℃生长的Ge量子点插入层,制备出薄的SiGe驰豫缓冲层(虚衬底),表面Ge组份达到0.25,表面粗糙度小于2nm,驰豫度接近100%.在我们制备的SiGe缓冲层上外延了应变补偿SiGe/Si多量子阱结构,并初步研究了其发光特性.

  18. Superlattice Multinanolayered Thin Films of SiO2/SiO2 + Ge for Thermoelectric Device Applications

    Science.gov (United States)

    2013-04-05

    REPORT Superlattice multinanolayered thin films of SiO2/SiO2 + Ge for thermoelectric device applications 14. ABSTRACT 16. SECURITY CLASSIFICATION OF...used as a physical vapor deposition ( PVD ) system since we have used only two electron guns to evaporate the crucibles without any gas assistance. The

  19. Electron irradiation effects on DC electrical performances of SiGe HBT in a comparison with Si BJT

    Institute of Scientific and Technical Information of China (English)

    MENG Xiangti; ZHANG Ximin; WANG Jilin; HUANG Wentiao; CHEN Peiyi; JIA Hongyong; TSIEN Peihsin

    2004-01-01

    The DC characteristics of SiGe HBT irradiated at different electron dose have been studied in a comparison with those of Si BJT. Generally, Ib and Ib - Ib0 increase, Ic, Ic - Ic0 and its +/- transition Vbe as well as DC current gainβ decreases with increasing dose; increase of Ib - Ib0 with increasing dose for Si BJT is much larger than that for SiGe HBT;β increases with Vbe or Ib, but decreases at Ib < 0.25 mA with Ib, and congregates at higher dose; and a damage factor d(β) is much less at the same dose for SiGe HBT than for Si BJT. SiGe HBT has much better anti-radiation performance than Si BJT. Some anomalous phenomena for increase of Ic, Ic - Ic0,Ib - Ib0 and β at low dose have been found. Some electron traps have been measured. The mechanism of changes of characteristics is discussed.

  20. Re-examination of the SiGe Raman spectra: Percolation/one-dimensional-cluster scheme and ab initio calculations

    Science.gov (United States)

    Pagès, O.; Souhabi, J.; Torres, V. J. B.; Postnikov, A. V.; Rustagi, K. C.

    2012-07-01

    We report on the detailed assignment of various features observed in the Raman spectra of SiGe alloys along the linear chain approximation (LCA), as achieved based on remarkable intensity interplays with composition between such neighboring features known from the literature but which so far have not been fully exploited. Such an assignment is independently supported by ab initio calculation of the frequencies of bond-stretching modes taking place in different local environments, which we define at one dimension (1D) for consistency with the LCA. Fair contour modeling of the SiGe Raman spectra is eventually obtained via a so-called 1D-cluster version of the phenomenological (LCA-based) percolation scheme, as originally developed for zincblende alloys, after ab initio calibration of the intrinsic Si-Si, Si-Ge, and Ge-Ge Raman efficiencies. The 1D-cluster scheme introduces a seven-oscillator [1 × (Ge-Ge), 4 × (Si-Ge), 2 × (Si-Si)] Raman behavior for SiGe, which considerably deviates from the currently accepted six-oscillator [1 × (Ge-Ge), 1 × (Si-Ge), 4 × (Si-Si)] behavior. Different numbers of Raman modes per bond are interpreted as different sensitivities to the local environment of Ge-Ge (insensitive), Si-Si (sensitive to first neighbors), and Si-Ge (sensitive to second neighbors) bond stretching. The as-obtained SiGe 1D-cluster/percolation scheme is also compared with the current version for zincblende alloys, using GaAsP as a natural reference. A marked deviation is concerned with an inversion of the like phonon branches in each multiplet. This is attributed either to the considerable Si and Ge phonon dispersions (Si-Si doublet) or to a basic difference in the lattice relaxations of diamond and zincblende alloys (Si-Ge multiplet). The SiGe vs GaAsP comparison is supported by ab initio calculation of the local lattice relaxation/dynamics related to prototype impurity motifs that are directly transposable to the two crystal structures.

  1. Comparison of Si+n and Ge+n(n=2-15) Cationic Structures

    Institute of Scientific and Technical Information of China (English)

    QIN Wei; ZANG Qing-jun; LU Wen-cai; WANG Cai-zhuang; HO Kai-ming

    2011-01-01

    We designed and optimized a large number of the isomers of Si12+ at the level of density functional theory (DFT)-B3LYP/6-311++G(d) using the Gaussian 03 software package. An unambiguous structure of the Si12+ cluster is presented, whose IR spectrum agrees well with the experiment result. The most stable geometric structures of Ge+n(n=2-15) clusters were determined by the all-electron PBE/DND method in DMol3 of the Material Studio Package, and compared with those of the corresponding Si+n geometries. Most structures of Ge+n and Si+n are similar except the ones of those for n=9, 12, 13 and 14, and the pentagonal bipyramid motif and the tri-capped trigonal prism(TTP) motif often appear in the Si+n and Ge+n(n=7-15) structures(except for Si14+).

  2. Design of a Si-based lattice-matched room-temperature GeSn/GeSiSn multi-quantum-well mid-infrared laser diode.

    Science.gov (United States)

    Sun, G; Soref, R A; Cheng, H H

    2010-09-13

    This paper presents modeling and simulation of a silicon-based group IV semiconductor injection laser diode in which the active region has a multiple quantum well structure formed with Ge(0.9)Sn(0.1) quantum wells separated by Ge(0.75)Si(0.1)Sn(0.15) barriers. These alloy compositions were chosen to satisfy three conditions simultaneously: a direct band gap for Ge(0.9)Sn(0.1), type-I band alignment between Ge(0.9)Sn(0.1) and Ge(0.75)Si(0.1)Sn(0.15,) and a lattice match between wells and barriers. This match ensures that the entire structure can be grown strain free upon a relaxed Ge(0.75)Si(0.1)Sn(0.15) buffer on a silicon substrate - a CMOS compatible process. Detailed analysis is performed for the type I band offsets, carrier lifetime, optical confinement, and modal gain. The carrier lifetime is found to be dominated by the spontaneous radiative process rather than the Auger process. The modal gain has a rather sensitive dependence on the number of quantum wells in the active region. The proposed laser is predicted to operate at 2.3 μm in the mid infrared at room temperature.

  3. Dynamic Tuning of Transmission Wavelength of MEMS-Based Ge Waveguides on a Si Beam

    Directory of Open Access Journals (Sweden)

    Masashi Hirase

    2016-03-01

    Full Text Available Three-dimensional structures of microelectro-mechanical systems (MEMS-based Ge waveguide on a Si beam were fabricated for dynamic tuning of the fundamental absorption edge of Ge by external stressing. The application of various amounts of external forces up to 1 GPa onto the Si beam shows clear red-shifts in the absorption edge of Ge waveguides on the Si beam by ~40 nm. This shift was reproduced by the deformation potential theory, considering that mode of propagation in the Ge waveguide. The wavelength tuning range obtained makes it possible to cover the whole C-band of optical communication, indicating it to be a promising approach to electro-absorption Ge modulators to get them to work with a broader wavelength range than previously reported.

  4. Influence of the step properties on submonolayer growth of Ge and Si at the Si(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Romanyuk, Konstantin

    2009-10-21

    The present work describes an experimental investigation of the influence of the step properties on the submonolayer growth at the Si(111) surface. In particular the influence of step properties on the morphology, shape and structural stability of 2D Si/Ge nanostructures was explored. Visualization, morphology and composition measurements of the 2D SiGe nanostructures were carried out by scanning tunneling microscopy (STM). The formation of Ge nanowire arrays on highly ordered kink-free Si stepped surfaces is demonstrated. The crystalline nanowires with minimal kink densities were grown using Bi surfactant mediated epitaxy. The nanowires extend over lengths larger than 1 {mu}m have a width of 4 nm. To achieve the desired growth conditions for the formation of such nanowire arrays, a modified variant of surfactant mediated epitaxy was explored. It was shown that controlling the surfactant coverage at the surface and/or at step edges modifies the growth properties of surface steps in a decisive way. The surfactant coverage at step edges can be associated with Bi passivation of the step edges. The analysis of island size distributions showed that the step edge passivation can be tuned independently by substrate temperature and by Bi rate deposition. The measurements of the island size distributions for Si and Ge in surfactant mediated growth reveal different scaling functions for different Bi deposition rates on Bi terminated Si(111) surface. The scaling function changes also with temperature. The main mechanism, which results in the difference of the scaling functions can be revealed with data of Kinetic Monte-Carlo simulations. According to the data of the Si island size distributions at different growth temperatures and different Bi deposition rates the change of SiGe island shape and preferred step directions were attributed to the change of the step edge passivation. It was shown that the change of the step edge passivation is followed by a change of the

  5. New members of the A2 M ‧ M2″ structure family (A=Ca, Sr, Yb, La; M ‧ = In , Sn , Pb; M ″ = Si , Ge)

    Science.gov (United States)

    Jehle, Michael; Dürr, Ines; Fink, Saskia; Lang, Britta; Langenmaier, Michael; Steckhan, Julia; Röhr, Caroline

    2015-01-01

    The new mixed tetrelides Sr2PbGe2 and Yb2SnGe2, several mixed Ca/Sr (AII) germanides A2II (Sn , Pb)Ge2 and two polymorphs of La2 InSi2 represent new members of the general structure family of ternary alkaline-earth/lanthanoid main group silicides/germanides A2 M ‧ M2″ (M ‧ = In , Sn , Pb ; M ″ = Si , Ge). All compounds were synthesized from melts of the elements and their crystal structures have been determined by means of single crystal X-ray diffraction. Sr2PbGe2 (Cmmm, a=402.36(11), b=1542.3(4), c=463.27(10) pm) crystallizes with the Mn2AlB2 -type structure. In exhibiting infinite planar Ge zig-zag chains, it represents one border of the compound series. The other borderline case, where only [Ge2 ] dumbbells are left as Ge building units, is represented by the Ca/Yb tin germanides Ca2SnGe2 and Yb2SnGe2 (Mo2FeB2 -type; P4/mbm, a=748.58(13)/740.27(7), c=445.59(8)/435.26(5) pm). In between these two border structures compounds with variable Si/Ge chain lengths could be obtained by varying the averaged size of the AII cations: Ca0.45Sr1.55PbGe2 (new structure type; Pbam, a=791.64(5), b=2311.2(2), c=458.53(3) pm) contains planar six-membered chain segments [Ge6 ]. Tetrameric pieces [Ge4 ] are the conspicuous structure elements in Ca1.16Sr0.84SnGe2 and La2 InSi2 (La2 InNi2 -type; Pbam, a=781.01(2)/762.01(13), b=1477.95(3)/1494.38(6), c=457.004(9)/442.1(3) pm). The tetragonal form of 'La2 In Si2‧ (exact composition: La2In1.07Si1.93, P4/mbm, a=1309.11(12), c=443.32(4) pm) also crystallizes in a new structure type, containing only [Si3 ] trimers as cutouts of the planar chains. In all structures the Si/Ge zig-zag chains/chain segments are connected by In/Sn/Pb atoms to form planar M layers, which are separated by pure A layers. Band structure calculations within the FP-LAPW DFT approach together with the Zintl formalism, extended by the presence of hypervalent bonding of the heavier M ‧ elements, give insight into the chemical bonding of this series of p

  6. Uniform fabrication of Ge nanocrystals embedded into SiO2 film via neutron transmutation doping

    Directory of Open Access Journals (Sweden)

    Wei Liu

    2014-06-01

    Full Text Available Nanocrystalline 74Ge embedded SiO2 films were prepared by employing ion implantation and neutron transmutation doping methods. Transmission electron microscopy, energy dispersive x-ray spectroscopy, and photoluminescence of the obtained samples were measured. The existence of As dopants transmuted from 74Ge is significant to guarantee the uniformity and higher volume density of Ge nanocrystals by tuning the system׳s crystallinity and activating mass transfer process. It was observed that the photoluminescence intensity of Ge nanocrystals increased first then decreased with the increase of arsenic concentration. The optimized fluence of neutron transmutation doping was found to be 5.5×1017 cm−2 to achieve maximum photoluminescence emission in Ge embedded SiO2 film. This work opens a route in the three-dimensional nanofabrication of uniform Ge nanocrystals.

  7. Influence of absorber layer dopants on performance of Ge/Si single photon avalanche diodes

    Science.gov (United States)

    Pilgrim, Neil J.; Ikonic, Zoran; Kelsall, Robert W.

    2013-04-01

    Monte Carlo electronic transport simulations are applied to investigate the influence of the Ge absorber layer on the performance of Ge/Si single photon avalanche diodes. Ge dopant type and concentration control the internal electric field gradients, which directly influence the probabilistic distribution of times from the point of charge photo-generation to that of transmission over the Ge/Si heterojunction. The electric field adjacent to the heterointerface is found to be the dominant factor in achieving rapid transmission, leading to a preference for p-type dopants in the Ge absorber. The contribution to jitter from the Ge layer is estimated and appears relatively independent of bias, though scales near-linearly with layer height.

  8. Effect of nanocavities on Ge nanoclustering and out-diffusion in SiO2

    Science.gov (United States)

    Li, Chen; Feng, Honglei; Liu, Bin; Liang, Wenshuang; Liu, Guiju; Ross, Guy G.; Wang, Yiqian; Barba, David

    2017-01-01

    Germanium nanocrystals (Ge-ncs) were synthesized by implantation of Ge+ ions into the fused silica, followed by a thermal annealing at 1000 °C. High-resolution transmission electron microscopy was employed to characterize both the morphology of the formed Ge-ncs and the evolution of their depth-distribution as a function of annealing durations. The formation of nanocavities in the vicinity of nanocrystal/SiO2 interface is evidenced, as well as their influence on the release of the compressive stress exerted on Ge-ncs by surrounding SiO2. Some Ge-ncs are found inside nanocavities, and can move into the implanted layer through a nanocavity-assisted diffusion mechanism. This finding sheds light on a new process that can explain the non-uniformity of the Ge-nanocrystal spatial distribution.

  9. Uniform fabrication of Ge nanocrystals embedded into SiO2 film via neutron transmutation doping

    Institute of Scientific and Technical Information of China (English)

    Wei Liu; Tiecheng Lu; Qingyun Chen; Youwen Hu; Shaobo Dun; Issai Shlimak

    2014-01-01

    Nanocrystalline 74Ge embedded SiO2 films were prepared by employing ion implantation and neutron transmutation doping methods. Transmission electron microscopy, energy dispersive x-ray spectroscopy, and photoluminescence of the obtained samples were measured. The existence of As dopants transmuted from 74Ge is significant to guarantee the uniformity and higher volume density of Ge nanocrystals by tuning the system's crystallinity and activating mass transfer process. It was observed that the photoluminescence intensity of Ge nanocrystals increased first then decreased with the increase of arsenic concentration. The optimized fluence of neutron transmutation doping was found to be 5.5 ? 1017 cm ? 2 to achieve maximum photoluminescence emission in Ge embedded SiO2 film. This work opens a route in the three-dimensional nanofabrication of uniform Ge nanocrystals.

  10. Insights into microstructural evolution and polycrystalline compounds formation from Pd Ge thin films

    Science.gov (United States)

    Chen, Zhiwen; Shek, C. H.; Lai, J. K. L.

    2005-04-01

    Polycrystalline Pd-Ge thin films, prepared on freshly cleaved single crystal NaCl (1 0 0) substrate by evaporation techniques, were characterized for their composition, morphologies, and crystalline structure by transmission electron microscopy (TEM). The experimental results indicated that the formation of Pd 2Ge and PdGe compounds dominated at low annealing temperatures, and it also affected the crystallization of amorphous Ge. The reactions of Pd and Ge are sensitively dependent on the annealing temperatures and the thickness ratio of Pd and Ge films. The crystallization of amorphous Ge and the reactions of Pd and Ge are mutually competitive in polycrystalline Pd-Ge thin films. The grain nucleation, growth, and aggregation in Pd-Ge thin films during processing are discussed in terms of the fundamental kinetic processes.

  11. Insights into microstructural evolution and polycrystalline compounds formation from Pd-Ge thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chen Zhiwen [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China)]. E-mail: cnzwchen@yahoo.com.cn; Shek, C.H. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China); Lai, J.K.L. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China)

    2005-04-15

    Polycrystalline Pd-Ge thin films, prepared on freshly cleaved single crystal NaCl (1 0 0) substrate by evaporation techniques, were characterized for their composition, morphologies, and crystalline structure by transmission electron microscopy (TEM). The experimental results indicated that the formation of Pd{sub 2}Ge and PdGe compounds dominated at low annealing temperatures, and it also affected the crystallization of amorphous Ge. The reactions of Pd and Ge are sensitively dependent on the annealing temperatures and the thickness ratio of Pd and Ge films. The crystallization of amorphous Ge and the reactions of Pd and Ge are mutually competitive in polycrystalline Pd-Ge thin films. The grain nucleation, growth, and aggregation in Pd-Ge thin films during processing are discussed in terms of the fundamental kinetic processes.

  12. Delayed plastic relaxation limit in SiGe islands grown by Ge diffusion from a local source

    Energy Technology Data Exchange (ETDEWEB)

    Vanacore, G. M.; Zani, M.; Tagliaferri, A., E-mail: alberto.tagliaferri@polimi.it [CNISM-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Nicotra, G. [IMM-CNR, Stradale Primosole 50, I-95121 Catania (Italy); Bollani, M. [CNR-IFN, LNESS, Via Anzani 42, I-22100 Como (Italy); Bonera, E.; Montalenti, F.; Picco, A.; Boioli, F. [Dipartimento di Scienza dei Materiali and L-NESS, Università Milano-Bicocca, via Cozzi 53, I-20125 Milano (Italy); Capellini, G. [Department of Sciences at the Università Roma Tre, Via Vasca Navale 79, 00146 Roma (Italy); Isella, G. [CNISM, LNESS, Dipartimento di Fisica, Politecnico di Milano (Polo di Como), Via Anzani 42, I-22100 Como (Italy); Osmond, J. [ICFO–The Institute of Photonic Sciences, Av. Carl Friedrich Gauss, 3, E-08860 Castelldefels (Barcelona) (Spain)

    2015-03-14

    The hetero-epitaxial strain relaxation in nano-scale systems plays a fundamental role in shaping their properties. Here, the elastic and plastic relaxation of self-assembled SiGe islands grown by surface-thermal-diffusion from a local Ge solid source on Si(100) are studied by atomic force and transmission electron microscopies, enabling the simultaneous investigation of the strain relaxation in different dynamical regimes. Islands grown by this technique remain dislocation-free and preserve a structural coherence with the substrate for a base width as large as 350 nm. The results indicate that a delay of the plastic relaxation is promoted by an enhanced Si-Ge intermixing, induced by the surface-thermal-diffusion, which takes place already in the SiGe overlayer before the formation of a critical nucleus. The local entropy of mixing dominates, leading the system toward a thermodynamic equilibrium, where non-dislocated, shallow islands with a low residual stress are energetically stable. These findings elucidate the role of the interface dynamics in modulating the lattice distortion at the nano-scale, and highlight the potential use of our growth strategy to create composition and strain-controlled nano-structures for new-generation devices.

  13. Electronic Properties of Strained Si/Ge Core-Shell Nanowires

    CERN Document Server

    Peng, Xihong

    2010-01-01

    We investigated the electronic properties of strained Si/Ge core-shell nanowires along the [110] direction using first principles calculations based on density-functional theory. The diameter of the studied core-shell wire is up to 5 nm. We found the band gap of the core-shell wire is smaller than that of both pure Si and Ge wires with the same diameter. This reduced band gap is ascribed to the intrinsic strain between Ge and Si layers, which partially counters the quantum confinement effect. The external strain is further applied to the nanowires for tuning the band structure and band gap. By applying sufficient tensile strain, we found the band gap of Si-core/Ge-shell nanowire with diameter larger than ~3 nm experiences a transition from direct to indirect gap.

  14. SiGe-based re-engineering of electronic warfare subsystems

    CERN Document Server

    Lambrechts, Wynand

    2017-01-01

    This book equips readers with a thorough understanding of the applicability of new-generation silicon-germanium (SiGe) electronic subsystems for the military purposes of electronic warfare and defensive countermeasures. The theoretical and technical background is extensively explained and all aspects of the integration of SiGe as an enabling technology for maritime, land, and airborne (including space) electronic warfare are addressed, including research, design, development, and implementation. The coverage is supported by mathematical derivations, informative illustrations, practical examples, and case studies. While SiGe technology provides speed, performance, and price advantages in many markets, sharing of information on its use in electronic warfare systems has to date been limited, especially in developing nations. This book will therefore be warmly welcomed as an engineering guideline that focuses especially on the speed and reliability of current-generation SiGe circuits and highlights emerging innov...

  15. Microstructure and properties of Ti-rich Ti-Si-Ge-Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bulanova, M.; Tretyachenko, L.; Golovkova, M.; Soroka, A. [AN Ukrainskoj SSR, Kiev (Ukraine). Inst. Problem Materialovedeniya

    1998-11-01

    Using differential thermal analysis, X-ray diffraction, microscopy and electron microprobe, phase equilibria in the Ti-rich corner of the Ti-Si-Ge-Al system were studied. Projections of the solidus and liquidus surfaces were constructed. At the solidus temperatures Ti{sub 5}(Si,Ge,Al){sub 3} (Z) phase coexists with left angle {beta}-Ti right angle -based solid solution ({beta}), resulting in a wide two-phase {beta} + Z region. The solidus surface has a temperature maximum at 1540 C for 70Ti-5Si-5Ge-20Al. The isopleth at 5 at.% Si + 5 at.% Ge is given. The liquidus surface is characterised by the bivariant eutectic surface L <=> {beta} + Z. Microhardness of the primary phases, corresponding to the boundaries of the homogeneity ranges, and eutectic mixtures was measured. Partial substitution of silicon for germanium does neither change the character of the phase equilibria nor the temperatures of phase transformations. (orig.) 9 refs.

  16. Boron diffusion in Ge{sup +} premorphized and BF{sub 2} implanted Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Zou, L.F.; Acosta-Ortiz, S.E. [Centro de Investigaciones en Optica, A.C. Unidad Aguascalientes, Juan de Montoro No. 207, Zona Centro, 20000 Aguascalientes (Mexico); Zou, L.X. [Computer Science Department, Zhongnan University for Nationalities Wuhan, Hubei 430074 (China); Regalado, L.E. [Centro de Investigaciones en Optica, Loma del Bosque No. 115, Loma del Campestre, 37000 Leon, Gunajuato (Mexico); Sun, D.Z.; Wang, Z.G. [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, (China)

    1998-12-31

    The annealing behavior of Si implanted with Ge and then BF{sub 2} has been characterized by double crystal X-ray diffraction (DCXRD) and secondary ion mass spectroscopy (SIMS). The results show that annealing at 600 Centigrade for 60 minutes can only remove a little damage induced by implantation and nearly no redistribution of Ge and B atoms has occurred during the annealing. The initial crystallinity of Si is fully recovered after annealing at 950 Centigrade for 60 minutes and accompanied by Ge diffusion. Very shallow boron junction depth has been formed. When annealing temperature rises to 1050 Centigrade, B diffusion enhances, which leads to a deep diffusion and good distribution of B atoms into the Si substrate. The X-ray diffraction (004) rocking curves from the samples annealed at 1050 Centigrade for 60 minutes display two Si Ge peaks, which may be related to the B concentration profiles. (Author)

  17. Optical and structural investigations of self-assembled Ge/Si bi-layer containing Ge QDs

    Energy Technology Data Exchange (ETDEWEB)

    Samavati, Alireza, E-mail: alireza.samavati@yahoo.com [Ibn Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia); Othaman, Z., E-mail: zulothaman@gmail.com [Ibn Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia); Ghoshal, S.K.; Dousti, M.R. [Advanced Optical Material Research Group, Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

    2014-10-15

    We report the influence of Si spacer thickness variation (10–40 nm) on structural and optical properties of Ge quantum dots (QDs) in Ge/Si(1 0 0) bi-layer grown by radio frequency magnetron sputtering. AFM images reveal the spacer dependent width, height, root mean square roughness and number density of QDs vary in the range of ∼12–25 nm, ∼2–6 nm, ∼1.95–1.05 nm and ∼0.55×10{sup 11}–2.1×10{sup 11} cm{sup −2}, respectively. XRD patterns exhibit the presence of poly-oriented structures of Ge with preferred growth along (1 1 1) direction accompanied by a reduction in strain from 4.9% to 1.2% (estimated from Williamson–Hall plot) due to bi-layering. The room temperature luminescence displays strong blue–violet peak associated with a blue shift as much as 0.05 eV upon increasing the thickness of Si spacer. This shift is attributed to the quantum size effect, the material intermixing and the strain mediation. Raman spectra for both mono and bi-layer samples show intense Ge–Ge optical phonon mode that is shifted towards higher frequency. Furthermore, the first order features of Raman spectra affirm the occurrence of interfacial intermixing and phase formation during deposition. The excellent features of the results suggest that our systematic method may constitute a basis for the tunable growth of Ge QDs suitable in nanophotonics. - Highlights: • High quality bilayered hetero-structure Ge/Si using economic and easy rf magnetron sputtering fabrication method. • The role of phonon-confinement and strain relaxation mechanisms. • Influence of bilayering on evolutionary growth dynamics. • Band gap shift of visible PL upon bilayering.

  18. Spin Dependent Transport in Si/SiGe Few-Electron Quantum Dots

    Science.gov (United States)

    Simmons, Christie

    2008-03-01

    Si/SiGe quantum dots are of interest for quantum information processing due in large part to the existence of spin zero isotopes of both Si and Ge. We present the results of transport measurements and integrated charge sensing in silicon double and single quantum dots.[1,2] We observe two effects arising from spin dependent transport in a double quantum dot. First, and as expected, for one direction of current flow we observe spin blockade -- the canonical example of spin-to-charge conversion in transport. In addition, when current flow is reversed, we observe a second effect: strong tails of current extend from the sharp triangular regions in which current conventionally is observed. The presence of these tails is explained by a combination of long spin relaxation times and preferential loading of an excited spin state. We also present charge-sensing measurements of single and double quantum dots using an integrated quantum point contact. The charge sensor signal from single electron tunneling is well correlated with conventional transport through the system. When the tunnel barriers are large and transport through the dot is not measurable, charge sensing remains a viable means to track charge transitions and is used to confirm individual-electron occupation in a single quantum dot. Work performed in collaboration with Nakul Shaji, Madhu Thalakulam, Levente J. Klein, H. Luo, Hua Qin, R. H. Blick, D. E. Savage, M. G. Lagally, A. J. Rimberg, R. Joynt, M. Friesen, S. N. Coppersmith, M. A. Eriksson. Work supported by ARO, LPS, NSF and DOE. (1) Shaji, N. et al. e-print arXiv:0708.0794 (2) Simmons, C. B. et al. Appl. Phys. Lett. 91, 213103 (2007).

  19. Structural and electronic properties of non-magnetic intermetallic YAuX (X = Ge and Si) in hexagonal and cubic phases

    Indian Academy of Sciences (India)

    A Lekhal; F Z Benkhelifa; S Méçabih; B Abbar; B Bouhafs

    2016-02-01

    The structural and electronic properties of non-magnetic intermetallic YAuX (X = Ge and Si) crystallized in hexagonal phase have been investigated using the full potential linearized augmented-plane wave (FPLAPW) method based on the density functional theory (DFT), within the generalized gradient approximation (GGA). The calculated lattice parameters were in good agreement with experiment. Also, the structural and electronic properties of the non-magnetic half-Heusler YAuPb compound including the artificial YAuX (X = Ge and Si) calculated in cubic phase were determined. It was found that the half-Heusler YAuPb compound presented metallic character. The results showed that YAuGe in cubic phase is a semiconductor whereas the cubic YAuSi is an isolator.

  20. Photoluminescence from Ge-SiO2 thin films and its mechanism

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ge-SiO2 thin films were deposited on p-type Si substrates using the radio frequency (rf) magnetron sputtering technique with a Ge-SiO2 composite target. Films were annealed in N2 ambience for 30 min at 300℃-1000℃ with an interval of 100℃. Through the X-ray diffraction, the average size of Ge nanocrystals (nc-Ge) was determined. They increased from 3.9 to 6.1 nm with increasing annealing temperature in the range of 600℃-1000℃. Under ultravio-let excitation, all samples emit a strong violet band centered at 396 nm. With the formation of nc-Ge, the samples exhibit another emission of orange band with the peak at 580 nm and its intensity increases with the increasing size of nc-Ge. The peak positions of two bands do not shift obviously. Ex-perimental data indicate that the violet band comes from GeO defect and the orange band originates mainly from the luminescence centers at the interface between the nc-Ge and SiO2 matrix.

  1. New monocrystalline Si{sub 1-x}Ge{sub x} solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Losada, B.R.; Moehlecke, A.; Ruiz, J.M.; Luque, A. [Universidad Politecnica de Madrid (Spain)] [and others

    1995-08-01

    The development of solar cells on Si{sub 1-x}Ge{sub x} might be interesting because they might present more current photo-response than the silicon cells, based on the lower bandgap of the alloyed crystal. In particular the use of Si{sub 1-x}Ge{sub x} solar cells in dual bandgap concentration structures as GaAs/Si{sub 1-x}Ge{sub x} can lead to total efficiency increase of about 1% as compared to the GaAs/Si structure, according to our calculations. Our effort is devoted to solar cells with low content of Ge, lower than 20% at. This choice is based on two previous hypothesis (1) A low content of Ge suggests that the well known silicon cell process, slightly modified, can be applied to the Si{sub 1-x}Ge{sub x} cells. (2) Calculations suggest that for utilisation in tandem with GaAs cells, the gain of efficiency is low above 20at % Ge.

  2. Electron Spin Resonance on Mobile and Confined States in Gated Modulation Doped Si/SiGe Heterostructures

    Science.gov (United States)

    He, Jianhua; Malissa, H.; Lu, Tzu-Ming; Shankar, S.; Tyryshkin, A. M.; Lyon, S. A.; Chen, Hung-Ming; Kuan, Chieh-Hsiung

    2010-03-01

    Electron spins in quantum dots in Si/SiGe heterostructures are promising qubits but controlling and measuring spins in gated dots is challenging. Fortunately, electrons confined into natural quantum dots by interface disorder can capture the spin physics with minimal processing, exhibiting long T1 and T2 at the Si/SiO2 interface^1. Natural quantum dots in the Si/SiGe system may be similarly useful. As a first step, we have fabricated a 2.2 x 13mm^2 Hall bar on a Si/SiGe substrate gated with an Al gate above an Al2O3 insulator, and performed electron spin resonance (ESR) at gate voltages above and below threshold. The ESR signal arising from the Si quantum well evolves with gate voltage, and its intensity (spin susceptibility) is measured as a function of temperature down to 0.4K. The susceptibility follows a Pauli dependence when the gate is biased above threshold, while it is Curie-like below threshold, indicating an evolution from a mobile 2D system towards localized states confined in natural dots by the intrinsic disorder in the quantum well. This work is supported by LPS and ARO. [1] S. Shankar, et al., Physica E, 40, 1659-1661 (2008).

  3. Capture, storage, and emission of holes in Si/Si 1- xGe x/Si QW's for the determination of the valence band offset by DLTS

    Science.gov (United States)

    Chretien, O.; Apetz, R.; Vescan, L.; Souifi, A.; Lüth, H.

    1996-08-01

    We report on the problem of the determination of the valence band offset between strained Si 1- xGe x and unstrained Si layers by deep level transient spectroscopy (DLTS) on Si/Si 1- xGe x/Si quantum well (QW) structures. To observe a DLTS signal, the holes must be stored long enough (>1 ms) in the QW so that the thermal emission is the dominating process. We achieved sufficiently long storage times by using two different structures. The first one was obtained by selective growth which leads to a lateral limitation of the QW-layer, where the holes are localized. For the second ones, the localization of holes is due to the presence of Si 1- xGe x-islands.

  4. Selective Etching of Silicon in Preference to Germanium and Si0.5Ge0.5.

    Science.gov (United States)

    Ahles, Christopher F; Choi, Jong Youn; Wolf, Steven; Kummel, Andrew C

    2017-06-21

    The selective etching characteristics of silicon, germanium, and Si0.5Ge0.5 subjected to a downstream H2/CF4/Ar plasma have been studied using a pair of in situ quartz crystal microbalances (QCMs) and X-ray photoelectron spectroscopy (XPS). At 50 °C and 760 mTorr, Si can be etched in preference to Ge and Si0.5Ge0.5, with an essentially infinite Si/Ge etch-rate ratio (ERR), whereas for Si/Si0.5Ge0.5, the ERR is infinite at 22 °C and 760 mTorr. XPS data showed that the selectivity is due to the differential suppression of etching by a ∼2 ML thick CxHyFz layer formed by the H2/CF4/Ar plasma on Si, Ge, and Si0.5Ge0.5. The data are consistent with the less exothermic reaction of fluorine radicals with Ge or Si0.5Ge0.5 being strongly suppressed by the CxHyFz layer, whereas, on Si, the CxHyFz layer is not sufficient to completely suppress etching. Replacing H2 with D2 in the feed gas resulted in an inverse kinetic isotope effect (IKIE) where the Si and Si0.5Ge0.5 etch rates were increased by ∼30 times with retention of significant etch selectivity. The use of D2/CF4/Ar instead of H2/CF4/Ar resulted in less total carbon deposition on Si and Si0.5Ge0.5 and gave less Ge enrichment of Si0.5Ge0.5. These results are consistent with the selectivity being due to the differential suppression of etching by an angstrom-scale carbon layer.

  5. Room Temperature Electroluminescence from Tensile-Strained Si0.13Ge0.87/Ge Multiple Quantum Wells on a Ge Virtual Substrate

    Directory of Open Access Journals (Sweden)

    Guangyang Lin

    2016-09-01

    Full Text Available Direct band electroluminescence (EL from tensile-strained Si0.13Ge0.87/Ge multiple quantum wells (MQWs on a Ge virtual substrate (VS at room temperature is reported herein. Due to the competitive result of quantum confinement Stark effect and bandgap narrowing induced by tensile strain in Ge wells, electroluminescence from Γ1-HH1 transition in 12-nm Ge wells was observed at around 1550 nm. As injection current density increases, additional emission shoulders from Γ2-HH2 transition in Ge wells and Ge VS appeared at around 1300–1400 nm and 1600–1700 nm, respectively. The peak energy of EL shifted to the lower energy side superquadratically with an increase of injection current density as a result of the Joule heating effect. During the elevation of environmental temperature, EL intensity increased due to a reduction of energy between L and Γ valleys of Ge. Empirical fitting of the relationship between the integrated intensity of EL (L and injection current density (J with L~Jm shows that the m factor increased with injection current density, suggesting higher light emitting efficiency of the diode at larger injection current densities, which can be attributed to larger carrier occupations in the Γ valley and the heavy hole (HH valance band at higher temperatures.

  6. Scattering mechanisms in shallow undoped Si/SiGe quantum wells

    Directory of Open Access Journals (Sweden)

    D. Laroche

    2015-10-01

    Full Text Available We report the magneto-transport study and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with depth ranging from ∼ 100 nm to ∼ 10 nm away from the heterostructure surface. The peak mobility increases with depth, suggesting that charge centers near the oxide/semiconductor interface are the dominant scattering source. The power-law exponent of the electron mobility versus density curve, μ ∝ nα, is extracted as a function of the depth of the Si quantum well. At intermediate densities, the power-law dependence is characterized by α ∼ 2.3. At the highest achievable densities in the quantum wells buried at intermediate depth, an exponent α ∼ 5 is observed. We propose and show by simulations that this increase in the mobility dependence on the density can be explained by a non-equilibrium model where trapped electrons smooth out the potential landscape seen by the two-dimensional electron gas.

  7. Electron and hole separation in Ge nanocones formed on Si{sub 1−x}Ge{sub x} solid solution by Nd:YAG laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gorb, A., E-mail: g_alla@ukr.net [Department of Physics, Taras Shevchenko Kyiv National University, Kyiv 01601 (Ukraine); Korotchenkov, O.; Kuryliuk, V. [Department of Physics, Taras Shevchenko Kyiv National University, Kyiv 01601 (Ukraine); Medvid, A.; Mozolevskis, G. [Research Laboratory of Semiconductor Physics, Institute of Technical Physics, Riga Technical University, 14/24 Azenes Str., Riga, LV-1048 (Latvia); Nadtochiy, A.; Podolian, A. [Department of Physics, Taras Shevchenko Kyiv National University, Kyiv 01601 (Ukraine)

    2015-08-15

    Highlights: • Nd:YAG laser radiation forms Ge nanocones on the Si{sub 1−x}Ge{sub x} surface. • The laser irradiation significantly increases the surface photovoltage signal. • Technique provides carrier separation pathways without deteriorating the surface quality. • Technique is advantageous for developing photodetector and the light source devices. - Abstract: The photoelectric characteristics of Ge nanocone structures, which are formed on Si surfaces by Nd:YAG laser radiation, is reported. It is found that exposing the SiGe/Si structure to irradiation intensities as high as 1.0 MW/cm{sup 2} Nd:YAG laser base frequency, which corresponds to effective formation of Ge nanocones on SiGe solid solution, significantly increases the surface photovoltage signal. The photovoltage decays do not shorten significantly with irradiation, thus indicating the fact that laser irradiation technique used here is capable of preventing the generation of considerable amount of carrier traps and recombination centers in the SiGe/Si structure and nanocones. From photovoltaic evidence it is therefore inferred that the laser irradiation fabrication technique is capable of providing well-defined carrier separation pathways without deteriorating the quality of the SiGe/Si structure and nanocones. Therefore, this technique can provide a cost-effective means for producing more effective photodetection devices in the near infrared.

  8. GaAs/Ge crystals grown on Si substrates patterned down to the micron scale

    Energy Technology Data Exchange (ETDEWEB)

    Taboada, A. G., E-mail: gonzalez@phys.ethz.ch; Kreiliger, T.; Falub, C. V.; Känel, H. von [Laboratory for Solid State Physics, ETH Zürich, Otto-Stern-Weg. 1, CH-8093 Zürich (Switzerland); Meduňa, M. [Department of Condensed Matter Physics, Masaryk University, Kotlářská 2, CZ-61137 Brno (Czech Republic); CEITEC, Masaryk University Kamenice 5, CZ-60177 Brno (Czech Republic); Salvalaglio, M.; Miglio, L. [L-NESS, Department of Materials Science, Università di Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano (Italy); Isa, F. [Laboratory for Solid State Physics, ETH Zürich, Otto-Stern-Weg. 1, CH-8093 Zürich (Switzerland); L-NESS and Department of Physics, Politecnico di Milano, via Anzani 42, I-22100 Como (Italy); Barthazy Meier, E.; Müller, E. [Scientific Center for Optical and Electron Microscopy (ScopeM), ETH Zürich, Auguste-Piccard-Hof 1, CH-8093 Zürich (Switzerland); Isella, G. [L-NESS and Department of Physics, Politecnico di Milano, via Anzani 42, I-22100 Como (Italy)

    2016-02-07

    Monolithic integration of III-V compounds into high density Si integrated circuits is a key technological challenge for the next generation of optoelectronic devices. In this work, we report on the metal organic vapor phase epitaxy growth of strain-free GaAs crystals on Si substrates patterned down to the micron scale. The differences in thermal expansion coefficient and lattice parameter are adapted by a 2-μm-thick intermediate Ge layer grown by low-energy plasma enhanced chemical vapor deposition. The GaAs crystals evolve during growth towards a pyramidal shape, with lateral facets composed of (111) planes and an apex formed by (137) and (001) surfaces. The influence of the anisotropic GaAs growth kinetics on the final morphology is highlighted by means of scanning and transmission electron microscopy measurements. The effect of the Si pattern geometry, substrate orientation, and crystal aspect ratio on the GaAs structural properties was investigated by means of high resolution X-ray diffraction. The thermal strain relaxation process of GaAs crystals with different aspect ratio is discussed within the framework of linear elasticity theory by Finite Element Method simulations based on realistic geometries extracted from cross-sectional scanning electron microscopy images.

  9. Effects of low-temperature Si buffer thickness and SiGe oxidation on sensitivity of Si1-xGex nanowire

    Science.gov (United States)

    Lai, Yi-Lung; Chang, Tai-Yuan; Chang, Kow-Ming; Chen, Chu-Feng; Lai, Chiung-Hui; Chen, Yi-Ming; Jong-Woei Whang, Allen; Lai, Hui-Lung; Chen, Huai-Yi; Wang, Shiu-Yu

    2015-06-01

    Si1-xGex nanowire biosensors are attractive for their high sensitivity due to the large surface-to-volume ratio, high carrier mobility, and silicon compatibility. In this work, we study the effect of the thickness of the low-temperature Si (LT-Si) buffer layer on an insulator on the sensitivity of oxidized Si1-xGex nanowire samples with different Ge contents by increasing the Si buffer thickness from 20 to 60 nm. 3-Aminopropyltrimethoxysilane (APTMS) was used as a biochemical reagent. It was demonstrated that, with the proper Ge content and LT-Si buffer thickness, the sensitivity of the Si1-xGex nanowire is high and it can be further improved by Si1-xGex oxidation. This can be attributed to the reduction of the diameter to the nanometer order, which gives rise to an increased surface-to-volume ratio and further enhances the sensitivity of the biosensor.

  10. Ternary GeSiSn alloys: New opportunities for strain and band gap engineering using group-IV semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    D' Costa, V.R. [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States); Fang, Y.-Y.; Tolle, J.; Kouvetakis, J. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 (United States); Menendez, J. [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States)

    2010-02-26

    Ternary GeSiSn alloys have been recently demonstrated on Ge- and GeSn-buffered Si substrates. These alloys, with a two-dimensional compositional space, make it possible to decouple lattice constant and electronic structure for the first time in a group-IV system. This paper reviews the basic properties of the GeSiSn alloy, presents some new results on its optical properties, and discusses the approach that has been followed to model heterostructures containing GeSiSn layers for applications in modulators, quantum cascade lasers, and photovoltaics.

  11. Monolithic Ge-on-Si lasers for large-scale electronic-photonic integration

    Science.gov (United States)

    Liu, Jifeng; Kimerling, Lionel C.; Michel, Jurgen

    2012-09-01

    A silicon-based monolithic laser source has long been envisioned as a key enabling component for large-scale electronic-photonic integration in future generations of high-performance computation and communication systems. In this paper we present a comprehensive review on the development of monolithic Ge-on-Si lasers for this application. Starting with a historical review of light emission from the direct gap transition of Ge dating back to the 1960s, we focus on the rapid progress in band-engineered Ge-on-Si lasers in the past five years after a nearly 30-year gap in this research field. Ge has become an interesting candidate for active devices in Si photonics in the past decade due to its pseudo-direct gap behavior and compatibility with Si complementary metal oxide semiconductor (CMOS) processing. In 2007, we proposed combing tensile strain with n-type doping to compensate the energy difference between the direct and indirect band gap of Ge, thereby achieving net optical gain for CMOS-compatible diode lasers. Here we systematically present theoretical modeling, material growth methods, spontaneous emission, optical gain, and lasing under optical and electrical pumping from band-engineered Ge-on-Si, culminated by recently demonstrated electrically pumped Ge-on-Si lasers with >1 mW output in the communication wavelength window of 1500-1700 nm. The broad gain spectrum enables on-chip wavelength division multiplexing. A unique feature of band-engineered pseudo-direct gap Ge light emitters is that the emission intensity increases with temperature, exactly opposite to conventional direct gap semiconductor light-emitting devices. This extraordinary thermal anti-quenching behavior greatly facilitates monolithic integration on Si microchips where temperatures can reach up to 80 °C during operation. The same band-engineering approach can be extended to other pseudo-direct gap semiconductors, allowing us to achieve efficient light emission at wavelengths previously

  12. Tight-binding calculation of optical gain in tensile strained [001]-Ge/SiGe quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Pizzi, Giovanni [NEST-CNR-INFM and Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56127 Pisa (Italy); Virgilio, Michele; Grosso, Giuseppe, E-mail: g.pizzi@sns.it [NEST-CNR-INFM and Dipartimento di Fisica ' E. Fermi' , Universita di Pisa, Largo Pontecorvo 3, I-56127 Pisa (Italy)

    2010-02-05

    It is known that under a tensile strain of about 2% of the lattice constant, the energy of the bottom conduction state of bulk Ge at the {Gamma} point falls below the minimum at the L point, leading to a direct gap material. In this paper we investigate how the same condition is realized in tensile strained Ge quantum wells. By means of a tight-binding sp{sup 3}d{sup 5}s* model, we study tensile strained Ge/Si{sub 0.2}Ge{sub 0.8} multiple quantum well (MQW) heterostructures grown on a relaxed SiGeSn alloy buffer along the [001] direction. We focus on values of the strain fields at the crossover between the indirect and direct gap regime of the MQWs, and calculate band edge alignments, electronic band structures, and density of states. We also provide a numerical evaluation of the MQW material gain spectra for TE and TM polarization under realistic carrier injection levels, taking into account the leakages related to the occupation of the electronic states at the L point. The analysis of the different orbital contributions to the near-gap states of the complete structure allows us to give a clear interpretation of the numerical results for the strain-dependent TM/TE gain ratio. Our calculations demonstrate the effectiveness of the structures under consideration for light amplification.

  13. Characterization of Si/SiGe/Si Deposited on SIMOX SOI by Synchrotron Radiation X-Ray Double-crystal Topography

    Institute of Scientific and Technical Information of China (English)

    Ma Tongda; Tu Hailing; Hu Guangyong; Wang Jing

    2004-01-01

    The synchrotron X-ray double-crystal topography was employed to investigate the structure of Si/SiGe/Si deposited on SIMOX SOI. Rocking curves with three diffraction peaks were acquired before and after 180° rotation of samples. Double-crystal topographs taken at the full width at half maximum (FWHM) of the three peaks differ from each other. Many defects appear in the Si layers that are likely related to the tilt between SOI and epitaxial layers.

  14. Defect and dislocation structures in low-temperature-grown Ge and Ge{sub 1−x}Sn{sub x} epitaxial layers on Si(110) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kidowaki, Shohei [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Asano, Takanori [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Research Fellow of Japan Society for the Promotion of Science, 5-3-1, Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan); Shimura, Yosuke [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kurosawa, Masashi [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Taoka, Noriyuki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Nakatsuka, Osamu, E-mail: nakatuka@alice.xtal.nagoya-u.ac.jp [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Zaima, Shigeaki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2016-01-01

    We have investigated the epitaxial growth and crystalline properties of Ge{sub 1−x}Sn{sub x} layers on a Si(110) substrate. We found that the twin growth in the Ge epitaxial layer deposited on the Si(110) using molecular beam epitaxy at a low temperature of 200 °C can be effectively suppressed by the incorporation of 2.0% Sn. We also examined the strain relaxation of annealed Ge{sub 1−x}Sn{sub x}/Si(110) samples. The degree of strain relaxation is enhanced by the annealing process, and the threading dislocation in the Ge{sub 1−x}Sn{sub x} layers decreases from 10{sup 11} cm{sup −2} to 10{sup 10} cm{sup −2} because of the propagation of misfit dislocations. We also observed misfit dislocations formed at the Ge{sub 1−x}Sn{sub x}/Si interface, which would effectively promote isotropic strain relaxation in the Ge{sub 1−x}Sn{sub x} layers. - Highlights: • Suppression of twin in GeSn growth on Si(110) substrate • Isotropic strain relaxation of Ge and GeSn layers by misfit dislocation network • Achievement of high quality GeSn epitaxial layers on Si(110) by post deposition annealing.

  15. Effect of Substrate Doping in Relaxed SiGe Buffers on Strained Si 2DEG Quantum Devices

    Science.gov (United States)

    Yao, Kun; Gaevski, Mikhail; Chernyshov, Alexander; Rokhinson, Leonid; Mike, Curtin; Park, Ji-Soo; Fiorenza, James; Lochtefeld, Anthony; Sturm, James

    2009-03-01

    We describe the impact of Si substrate doping on the substrate leakage in strained Si two-dimensional electron gases (2DEG) on SiGe relaxed graded buffers and on quantum devices fabricated from the 2DEG. The best commercially available high quality SiGe relaxed buffers with 30% Ge content, grown at temperature above 1000^oC, have very low threading dislocation density (heterostructures were grown at 625-700^oC in a rapid thermal chemical vapor deposition (RTCVD). However, it is shown that the substrate doping (Arsenic) contributes to leakage current origin in relaxed buffers at liquid helium temperatures if the starting Si substrate is heavily doped (˜5E17cm-2). The leakage can be attributed to enhanced dopant diffusion along misfit dislocations and high diffusion rate of As in SiGe. The leakage current makes side gating of nanostructures in the 2DEG impossible. With a lightly doped substrate, to avoid leakage, we achieved a high quality 2DEG and successful side gating of a 2DEG quantum dot for a quantum point contact. This work is supported by the NSA under ARO contract number W911NF-05-1-0437.

  16. Growth and structural characterisation of Si/SiGe heterostructures for optoelectronic applications

    Science.gov (United States)

    Li, X. B.; Neave, J. H.; Norris, D. J.; Cullis, A. G.; Paul, D. J.; Kelsall, R. W.; Zhang, J.

    2005-02-01

    The availability of compliant substrates has opened new avenues to exploit SiGe materials for optoelectronic applications. In this paper, relevant issues including fabrication of compliant substrates through compositionally graded buffer layers, strain (stress) balance in active layer design and X-ray characterisation are discussed. Quantum cascade structures designed for light emitting devices at THz range are grown using a combination of low pressure chemical vapour deposition and gas source molecular beam epitaxy in a single growth system. The results of structural characterisation by X-ray diffraction and transmission electron microscopy show that by following stringent design criteria, active layer structures more than 4 μm thick with low threading dislocation density can be achieved. Electroluminance in the THz frequency range have been observed from these structures.

  17. Excitation Intensity Driven PL Shifts of SiGe Islands on Patterned and Planar Si(001 Substrates: Evidence for Ge-rich Dots in Islands

    Directory of Open Access Journals (Sweden)

    Brehm M

    2010-01-01

    Full Text Available Abstract For randomly nucleated SiGe/Si(001 islands, a significantly stronger blue-shift of the PL spectra as a function of the excitation intensity is observed when compared to islands grown on patterned substrates side by side within the same run in a solid source molecular beam epitaxy chamber. We ascribe this different PL behavior to the much larger inhomogeneity of the Ge distribution in islands on planar substrates when compared to islands grown on pit-patterned ones, as observed previously. 3D band-structure calculations show that Ge-rich inclusions of approximately 5 nm diameter at the apex of the islands can account for the observed differences in the PL spectra. The existence of such inclusions can be regarded as a quantum dot in an island and is in agreement with recent nano-tomography experiments.

  18. Influence of Tb substitution on low-field magnetocaloric effect in Gd5Si1.72Ge2.28 alloy

    Institute of Scientific and Technical Information of China (English)

    DENG Jian-qiu; ZHUANG Ying-hong; WANG Ri-chu; YANG Zhen; XU Bin

    2008-01-01

    The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd1-xTbx)5Si1.72-Ge2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry and magnetization measurements. The results show that suitable partial substitution of Tb in Gd5Si1.72Ge2.28 compound remains the first-order magnetic-crystallographic transition and enhances the magnetic entropy change, although Tb substitution decreases the Curie temperature (Tc) of the compounds. The magnetic entropy change of (Gd1-xTbx)5Si1.72Ge2.28 alloys retains a large value in the low magnetic field of 1.0 T.The maximum magnetic entropy change for (Gd0.80Tb0.20)5Si1.72Ge2.28 alloy in the magnetic field from 0 to 1.0 T reaches 8.7 J/(kg·K),which is nearly 4 times as large as that of (Gd0.3Dy0.7)5Si4 compound (|△Smax| = 2.24 J/(kg·K), TC = 198 K).

  19. A neutron diffraction study of the R{sub 15}Ge{sub 9}C compounds (R = Ce, Pr, Nd)

    Energy Technology Data Exchange (ETDEWEB)

    Tencé, S., E-mail: tence@icmcb-bordeaux.cnrs.fr [Université Grenoble Alpes, Institut Néel, BP166, F-38042 Grenoble (France); CNRS, Institut Néel, Rue des Martyrs, F-38042 Grenoble (France); Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Université de Bordeaux, 87 Avenue Docteur Albert Schweitzer, 33608 Pessac Cedex (France); Isnard, O. [Université Grenoble Alpes, Institut Néel, BP166, F-38042 Grenoble (France); CNRS, Institut Néel, Rue des Martyrs, F-38042 Grenoble (France); Wrubl, F. [Department of Chemistry, University of Genoa, Via Dodecaneso 31, 16146 Genoa (Italy); Manfrinetti, P. [Department of Chemistry, University of Genoa, Via Dodecaneso 31, 16146 Genoa (Italy); Institute SPIN – CNR, Corso Perrone 24, 16152 Genoa (Italy)

    2014-05-01

    Highlights: • Neutron diffraction study was performed on the germanides R{sub 15}Ge{sub 9}C (R = Ce, Pr, Nd). • The interstitial carbon atoms occupy mainly the site 2b in (1/3 2/3 ∼1/2). • The three compounds display canted ferromagnetic structures with k = [0 0 0]. • Carbon insertion strongly modifies the magnetic properties of the parent germanides. - Abstract: In this work we report the results of the neutron diffraction investigation performed on the germanides R{sub 15}Ge{sub 9}C, for R = Ce, Pr and Nd (La{sub 15}Ge{sub 9}Fe-type, hP50, P6{sub 3}mc, Z = 2), to refine the crystal superstructure of these compounds and determine their magnetic structures. The interstitial carbon atoms occupy mainly the 2b Wyckoff site in the position (1/3 2/3 ∼1/2) and also, with a smaller occupancy rate, the Wyckoff site 2a at (0 0 ∼1/2). In the magnetic state, the three compounds display predominantly a ferromagnetic behavior with the propagation vector k = [0 0 0]. These results are in agreement with the magnetization measurements, with T{sub C} = 10, 30 and 80 K as Curie temperature of Ce{sub 15}Ge{sub 9}C, Pr{sub 15}Ge{sub 9}C and Nd{sub 15}Ge{sub 9}C, respectively. Ce{sub 15}Ge{sub 9}C and Nd{sub 15}Ge{sub 9}C present a ferromagnetic alignment of the R moments along the c-axis and an antiferromagnetic spin arrangement within the (a–b) plane. For Pr{sub 15}Ge{sub 9}C the ferromagnetic contribution is found within the (a–b) plane, as previously observed for the isotypic compound Tb{sub 15}Si{sub 9}C. The carbides crystal structure possesses four inequivalent rare earth sites carrying different magnetic moments, leading to mean values of 0.9 μ{sub B}/Ce, 1.1 μ{sub B}/Pr and 2.2 μ{sub B}/Nd for Ce{sub 15}Ge{sub 9}C, Pr{sub 15}Ge{sub 9}C and Nd{sub 15}Ge{sub 9}C, respectively. The magnetic structures of these R{sub 15}Ge{sub 9}C compounds differ strongly from those of their parent R{sub 5}Ge{sub 3} germanides, but present strong similarities with the

  20. Study of strain in partially relaxed Ge epilayers on Si(100) substrate

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Ge epilayers of different thicknesses are grown by molecular-beam epitaxy with Sb as a surfactant on SI(100) substrates,X-ray diffraction illustrates that these Ge thin films are partially strained.and the strains decrease gradually with increasing epilayer thickness,Raman spectra reveal a downward shift of the Ge-Ge mode peak as the epilayer thickness increases.In the regions of high strain,the relationship between the Raman shift of this mode and the strain in the partially relaxed samples is considerably different from the linear relationship reported before,which is mainly attributed to the spatial confinement effect of phonons in a nanocrystal.

  1. Dispersion of nonresonant third-order nonlinearities in GeSiSn ternary alloys

    Science.gov (United States)

    De Leonardis, Francesco; Troia, Benedetto; Soref, Richard A.; Passaro, Vittorio M. N.

    2016-01-01

    Silicon (Si), tin (Sn), and germanium (Ge) alloys have attracted research attention as direct band gap semiconductors with applications in electronics and optoelectronics. In particular, GeSn field effect transistors can exhibit very high performance in terms of power reduction and operating speed because of the high electron drift mobility, while the SiGeSn system can be constructed using CMOS-compatible techniques to realize lasers, LED, and photodetectors. The wide Si, Ge and Sn transparencies allow the use of binary and ternary alloys extended to mid-IR wavelengths, where nonlinearities can also be employed. However, neither theoretical or experimental predictions of nonlinear features in SiGeSn alloys are reported in the literature. For the first time, a rigorous and detailed physical investigation is presented to estimate the two photon absorption (TPA) coefficient and the Kerr refractive index for the SiGeSn alloy up to 12 μm. The TPA spectrum, the effective TPA wavelength cut-off, and the Kerr nonlinear refractive index have been determined as a function of alloy compositions. The promising results achieved can pave the way to the demonstration of on-chip nonlinear-based applications, including mid-IR spectrometer-on-a-chip, all-optical wavelength down/up-conversion, frequency comb generation, quantum-correlated photon-pair source generation and supercontinuum source creation, as well as Raman lasing. PMID:27622979

  2. Dispersion of nonresonant third-order nonlinearities in GeSiSn ternary alloys

    Science.gov (United States)

    de Leonardis, Francesco; Troia, Benedetto; Soref, Richard A.; Passaro, Vittorio M. N.

    2016-09-01

    Silicon (Si), tin (Sn), and germanium (Ge) alloys have attracted research attention as direct band gap semiconductors with applications in electronics and optoelectronics. In particular, GeSn field effect transistors can exhibit very high performance in terms of power reduction and operating speed because of the high electron drift mobility, while the SiGeSn system can be constructed using CMOS-compatible techniques to realize lasers, LED, and photodetectors. The wide Si, Ge and Sn transparencies allow the use of binary and ternary alloys extended to mid-IR wavelengths, where nonlinearities can also be employed. However, neither theoretical or experimental predictions of nonlinear features in SiGeSn alloys are reported in the literature. For the first time, a rigorous and detailed physical investigation is presented to estimate the two photon absorption (TPA) coefficient and the Kerr refractive index for the SiGeSn alloy up to 12 μm. The TPA spectrum, the effective TPA wavelength cut-off, and the Kerr nonlinear refractive index have been determined as a function of alloy compositions. The promising results achieved can pave the way to the demonstration of on-chip nonlinear-based applications, including mid-IR spectrometer-on-a-chip, all-optical wavelength down/up-conversion, frequency comb generation, quantum-correlated photon-pair source generation and supercontinuum source creation, as well as Raman lasing.

  3. SiGeSn Ternaries for Efficient Group IV Heterostructure Light Emitters.

    Science.gov (United States)

    von den Driesch, Nils; Stange, Daniela; Wirths, Stephan; Rainko, Denis; Povstugar, Ivan; Savenko, Aleksei; Breuer, Uwe; Geiger, Richard; Sigg, Hans; Ikonic, Zoran; Hartmann, Jean-Michel; Grützmacher, Detlev; Mantl, Siegfried; Buca, Dan

    2017-02-03

    SiGeSn ternaries are grown on Ge-buffered Si wafers incorporating Si or Sn contents of up to 15 at%. The ternaries exhibit layer thicknesses up to 600 nm, while maintaining a high crystalline quality. Tuning of stoichiometry and strain, as shown by means of absorption measurements, allows bandgap engineering in the short-wave infrared range of up to about 2.6 µm. Temperature-dependent photoluminescence experiments indicate ternaries near the indirect-to-direct bandgap transition, proving their potential for ternary-based light emitters in the aforementioned optical range. The ternaries' layer relaxation is also monitored to explore their use as strain-relaxed buffers, since they are of interest not only for light emitting diodes investigated in this paper but also for many other optoelectronic and electronic applications. In particular, the authors have epitaxially grown a GeSn/SiGeSn multiquantum well heterostructure, which employs SiGeSn as barrier material to efficiently confine carriers in GeSn wells. Strong room temperature light emission from fabricated light emitting diodes proves the high potential of this heterostructure approach.

  4. Synthesis and size differentiation of Ge nanocrystals in amorphous SiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Agan, S. [University of Illinois, Department of Materials Science and Engineering, Urbana, IL (United States); Kirikale University, Physics Department, Kirikale (Turkey); Celik-Aktas, A. [University of Illinois, Department of Nuclear, Plasma and Radiological Engineering, Urbana, IL (United States); Zuo, J.M. [University of Illinois, Department of Materials Science and Engineering, Urbana, IL (United States); Dana, A.; Aydinli, A. [Bilkent University, Physics Department, Ankara (Turkey)

    2006-04-15

    Germanosilicate layers were grown on Si substrates by plasma enhanced chemical vapor deposition (PECVD) and annealed at different temperatures ranging from 700-1010 C for durations of 5 to 60 min. Transmission electron microscopy (TEM) was used to investigate Ge nanocrystal formation in SiO{sub 2}:Ge films. High-resolution cross section TEM images, electron energy-loss spectroscopy and energy dispersive X-ray analysis (EDX) data indicate that Ge nanocrystals are present in the amorphous silicon dioxide films. These nanocrystals are formed in two spatially separated layers with average sizes of 15 and 50 nm, respectively. EDX analysis indicates that Ge also diffuses into the Si substrate. (orig.)

  5. Nitride passivation of the interface between high-k dielectrics and SiGe

    Energy Technology Data Exchange (ETDEWEB)

    Sardashti, Kasra [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358 (United States); Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093-0411 (United States); Hu, Kai-Ting [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358 (United States); Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093-0411 (United States); Tang, Kechao; McIntyre, Paul [Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States); Madisetti, Shailesh; Oktyabrsky, Serge [Colleges of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, New York 12222 (United States); Siddiqui, Shariq; Sahu, Bhagawan [TD Research, GLOBALFOUNDRIES US, Inc., Albany, New York 12203 (United States); Yoshida, Naomi; Kachian, Jessica; Dong, Lin [Applied Materials, Inc., Santa Clara, California 95054 (United States); Fruhberger, Bernd [California Institute for Telecommunications and Information Technology, University of California San Diego, La Jolla, California 92093-0436 (United States); Kummel, Andrew C., E-mail: akummel@ucsd.edu [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358 (United States)

    2016-01-04

    In-situ direct ammonia (NH{sub 3}) plasma nitridation has been used to passivate the Al{sub 2}O{sub 3}/SiGe interfaces with Si nitride and oxynitride. X-ray photoelectron spectroscopy of the buried Al{sub 2}O{sub 3}/SiGe interface shows that NH{sub 3} plasma pre-treatment should be performed at high temperatures (300 °C) to fully prevent Ge nitride and oxynitride formation at the interface and Ge out-diffusion into the oxide. C-V and I-V spectroscopy results show a lower density of interface traps and smaller gate leakage for samples with plasma nitridation at 300 °C.

  6. Direct measurement of the magnetocaloric effect in MnFe(P,X)(X = As, Ge, Si) materials

    Science.gov (United States)

    Yibole, H.; Guillou, F.; Zhang, L.; van Dijk, N. H.; Brück, E.

    2014-02-01

    An investigation of the magnetocaloric effect (MCE) displayed by three generations of MnFe(P,X) (X = As, Ge, Si) materials has been carried out by combining indirect ΔS and direct ΔTad measurements. To be able to compare the performances of the new Si-based system with the already well-known As- and Ge-based materials in optimal conditions, both the Mn/Fe and P/Si ratios of the MnxFe1.95-xP1-ySiy compounds were optimized to display the largest MCE around room temperature. Here, we show that the maximum values of ΔTad (ΔB = 1.1 T) and ΔS (ΔB = 1 T) are respectively ˜2.2 K and ˜8 J kg-1 K-1 in the Si-based material Mn1.25Fe0.7P0.49Si0.51. These values are very close to the MCE performances of the As-based and Ge-based compounds. A critical comparison of these three MnFe(P,X) series highlights the role played by the non-magnetic elements on the latent heat at the Curie temperature. The combination of: (i) large ΔS and ΔTad in intermediate magnetic fields, (ii) limited thermal/magnetic hysteresis, (iii) easy tunability of the Curie temperatures and (iv) practical advantages like cheap, non-critical and non-toxic starting materials; makes the MnxFe1.95-xP1-ySiy family highly promising for magnetic refrigeration applications.

  7. Design and development of SiGe based near-infrared photodetectors

    Science.gov (United States)

    Zeller, John W.; Puri, Yash R.; Sood, Ashok K.; McMahon, Shane; Efsthadiatis, Harry; Haldar, Pradeep; Dhar, Nibir K.

    2014-10-01

    Near-infrared (NIR) sensors operating at room temperatures are critical for a variety of commercial and military applications including detecting mortar fire and muzzle flashes. SiGe technology offers a low-cost alternative to conventional IR sensor technologies such as InGaAs, InSb, and HgCdTe for developing NIR micro-sensors that will not require any cooling and can operate with high bandwidths and comparatively low dark currents. Since Ge has a larger thermal expansion coefficient than Si, tensile strain may be incorporated into detector devices during the growth process, enabling an extended operating wavelength range above 1600 nm. SiGe based pin photodetectors have advantages of high stability, low noise, and high responsivity compared to metal-semiconductor-metal (MSM) devices. We have developed a process flow and are fabricating SiGe detector devices on 12" (300 mm) silicon wafers in order to take advantage of high throughput, large-area leading-edge silicon based CMOS technology that provides small feature sizes with associated device cost/density scaling advantages. The fabrication of the detector devices is facilitated by a two-step growth process incorporating initial low temperature growth of Ge/SiGe to form a thin strain-relaxed layer, followed by high temperature growth to deposit a thicker absorbing film, and subsequent high temperature anneal. This growth process is designed to effectively reduce dark current and enhance detector performance by reducing the number of defects and threading dislocations which form recombination centers during the growth process. Various characterization techniques have been employed to determine the properties of the epitaxially deposited Ge/SiGe layers, and the corresponding results are discussed.

  8. The Influence of Substitutions in 3 d-Sublattice on the Exchange Interactions in Compounds Based on NdMnGe

    Science.gov (United States)

    Ovchenkova, I. A.; Bogdanov, A. E.; Smirnov, A. V.; Ovchenkov, E. A.; Morozkin, A. V.; Yapaskurt, V. O.; Nikitin, S. A.

    2016-12-01

    Magnetic properties of CeFeSi-type NdMn_{1-x}TixGe compounds studied by magnetization and magnetocaloric measurements are reported. The increase in Ti content leads to the essential increase in magnetic ordering temperature of the Nd sublattice and the magnetocaloric effect. The results are compared with those obtained on isotypic RTX compounds and discussed assuming the itinerant character of magnetism of these compounds.

  9. Preparation and Properties of a Novel Al-Si-Ge-Zn Filler Metal for Brazing Aluminum

    Science.gov (United States)

    Niu, Zhiwei; Huang, Jihua; Yang, Hao; Chen, Shuhai; Zhao, Xingke

    2015-06-01

    The study is concerned with developing a filler metal with low melting temperature and good processability for brazing aluminum and its alloys. For this purpose, a novel Al-Si-Ge-Zn alloy was prepared according to Al-Si-Ge and Al-Si-Zn ternary phase diagrams. The melting characteristics, microstructures, wettability, and processing property of the alloy were investigated. The results showed that the melting temperature range of the novel filler metal was 505.2-545.1 °C, and the temperature interval between the solidus and the liquidus was 39.9 °C. Compared with a common Al-Si-Ge alloy, it had smaller and better dispersed β-GeSi solid solution precipitates, and the Zn-rich phases distributed on the boundary of the β-GeSi precipitates. The novel filler metal has good processability and good wettability with Al. There was one obvious transition layer with a thin α-Al solid solution between the filler metal and base metal, which is favorable to improve the strength of brazing joint.

  10. All-epitaxial Co{sub 2}FeSi/Ge/Co{sub 2}FeSi trilayers fabricated by Sn-induced low-temperature epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kawano, M.; Ikawa, M.; Arima, K.; Yamada, S.; Kanashima, T.; Hamaya, K., E-mail: hamaya@ee.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka 560-8531 (Japan)

    2016-01-28

    We demonstrate low-temperature growth of all-epitaxial Co{sub 2}FeSi/Ge/Co{sub 2}FeSi trilayer structures by developing Sn-induced surfactant-mediated molecular beam epitaxy (SMBE) of Ge on Co{sub 2}FeSi. Despite the growth of a semiconductor on a metal, we verify that the inserted Sn monolayers between Ge and Co{sub 2}FeSi enable to promote the 2D epitaxial growth of Ge up to 5 nm at a T{sub G} of 250 °C. An understanding of the mechanism of the Sn-induced SMBE leads to the achievement of all-epitaxial Co{sub 2}FeSi/Ge/Co{sub 2}FeSi trilayer structures with spin-valve-like magnetization reversals. This study will open a way for vertical-type and high-performance Ge-based spintronics devices.

  11. Structure and optical properties of Si and SiGe layers grown on SiO{sub 2} by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shklyaev, A.A., E-mail: shklyaev@isp.nsc.ru [A.V. Rzhanov Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Vdovin, V.I. [A.V. Rzhanov Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Volodin, V.A. [A.V. Rzhanov Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Gulyaev, D.V.; Kozhukhov, A.S. [A.V. Rzhanov Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Sakuraba, M.; Murota, J. [Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2015-03-31

    The properties of thin Si and SiGe layers grown on SiO{sub 2} by chemical vapor deposition (CVD) were studied using transmission electron and atomic force microscopies, and Raman and photoluminescence (PL) spectroscopies. The layers with a composition of Si{sub 0.5}Ge{sub 0.5} become composed of nanocrystals with an average size of about 100 nm at growth temperatures of 550 °C which is significantly lower than that for the pure Si layers. Moreover, the Si{sub 0.5}Ge{sub 0.5} layers exhibit a broad PL peak centered at 0.8 eV, whereas the bandgap of unstrained Si{sub 0.5}Ge{sub 0.5} is about 1 eV. This indicates that PL occurs through deep energy levels in the bandgap, which can be associated with crystal defects. The predominance of deep-level PL in radiative emission can be the result of a high concentration of defects that appear due to a low growth temperature. - Highlights: • The Si{sub 0.5}Ge{sub 0.5} layers grown on SiO{sub 2} become polycrystalline at 550 °C. • They exhibit a PL peak at 0.8 eV, whereas the Si{sub 0.5}Ge{sub 0.5} bandgap is about 1 eV. • Such properties make the layers interesting for applications in photonics.

  12. Misfit dislocation generation in SiGe epitaxial layers supersaturated with intrinsic point defects

    Energy Technology Data Exchange (ETDEWEB)

    Vdovin, V.I. [Institute for Chemical Problems of Microelectronics, B. Tolmachevsky per. 5, 119017 Moscow (Russian Federation)], E-mail: vivdov@gmail.com; Zakharov, N.D. [Max-Planck-Institut fuer Mikrostrukturphysik, 06120 Halle (Saale) (Germany)], E-mail: zakharov@mpi-halle.mpg.de

    2008-11-03

    Misfit dislocation generation in SiGe/Si(001) heterostructures supersaturated with the vacancies (LT epitaxial growth) or self-interstitials (ion implantation) was studied by transmission electron microscopy. A model of 'optimal' intrinsic point defects (IPDs) for effective strain relaxation is suggested and verified. Supersaturation of compressed SiGe layers with the vacancies ('optimal' IPDs) promotes high strain relaxation, whereas supersaturation with the self-interstitials ('inverse' IPDs) promotes a generation of V-shaped TDs which cannot extend to form MDs.

  13. Spectroscopic ellipsometric study of Ge nanocrystals embedded in SiO{sub 2} using parametric models

    Energy Technology Data Exchange (ETDEWEB)

    Petrik, P.; Fried, M. [Research Institute for Technical Physics and Materials Science, Budapest (Hungary); Dana, A.; Aydinli, A. [Institute of Materials Science and Nanotechnology, Bilkent University, Ankara (Turkey); Foss, S.; Finstad, T.G. [University of Oslo, Department of Physics, Blindern, Oslo (Norway); Basa, P.

    2008-05-15

    Ge-rich SiO{sub 2} layers on top of Si substrates were deposited using plasma enhanced chemical vapour deposition. Ge nanocrystals embedded in the SiO{sub 2} layers were formed by high temperature annealing. The samples were measured and evaluated by spectroscopic ellipsometry. Effective medium theory (EMT) and parametric semiconductor models have been used to model the dielectric function of the layers. Systematic dependences of the layer thickness and the oscillator parameters have been found on the annealing temperature (nanocrystal size). (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Molecular dynamics simulation of ion-beam-amorphization of Si, Ge and GaAs

    CERN Document Server

    Nord, J D; Keinonen, J

    2002-01-01

    We use molecular dynamics simulations to study ion-irradiation-induced amorphization in Si, Ge and GaAs using several different interatomic force models. We find that the coordination number is higher, and the average bond length longer, for the irradiated amorphous structures than for the molten ones in Si and Ge. For amorphous GaAs, we suggest that longer Ga-Ga bonds, also present in pure Ga, are produced during the irradiation. In Si the amorphization is found to proceed via growth of amorphous regions, and low energy recoils are found to induce athermal recrystallization during irradiation.

  15. Mid-infrared intersubband absorption from p-Ge quantum wells grown on Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Gallacher, K.; Millar, R. W.; Paul, D. J., E-mail: Douglas.Paul@glasgow.ac.uk [School of Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow G12 8LT (United Kingdom); Ballabio, A.; Frigerio, J.; Isella, G. [L-NESS, Dipartimento di Fisica del Politecnico di Milano, Polo Territoriale di Como, Via Anzani 42, Como I-22100 (Italy); Bashir, A.; MacLaren, I. [School of Physics and Astronomy, University of Glasgow, Kelvin Building, University Avenue, Glasgow G12 8QQ (United Kingdom); Ortolani, M. [Center for Life NanoScience@Sapienza, Istituto Italiano di Tecnologia, Viale Regina Elena 291, Rome I-00161 (Italy)

    2016-02-29

    Mid-infrared intersubband absorption from p-Ge quantum wells with Si{sub 0.5}Ge{sub 0.5} barriers grown on a Si substrate is demonstrated from 6 to 9 μm wavelength at room temperature and can be tuned by adjusting the quantum well thickness. Fourier transform infra-red transmission and photoluminescence measurements demonstrate clear absorption peaks corresponding to intersubband transitions among confined hole states. The work indicates an approach that will allow quantum well intersubband photodetectors to be realized on Si substrates in the important atmospheric transmission window of 8–13 μm.

  16. The electronic properties of bare and alkali metal adsorbed two-dimensional GeSi alloy sheet

    Science.gov (United States)

    Qiu, Wenhao; Ye, Han; Yu, Zhongyuan; Liu, Yumin

    2016-09-01

    In this paper, the structural and electronic properties of both bare and alkali metal (AM) atoms adsorbed two-dimensional GeSi alloy sheet (GeSiAS) are investigated by means of first-principles calculations. The band gaps of bare GeSiAS are shown slightly opened at Dirac point with the energy dispersion remain linear due to the spin-orbit coupling effect at all concentrations of Ge atoms. For metal adsorption, AM atoms (including Li, Na and K) prefer to occupy the hexagonal hollow site of GeSiAS and the primary chemical bond between AM adatom and GeSiAS is ionic. The adsorption energy has an increase tendency with the increase of the Ge concentration in supercell. Besides, single-side adsorption of AM atoms introduces band gap at Dirac point, which can be tuned by the Ge concentration and the species of AM atoms. The strong relation between the band gaps and the distribution of Si and Ge atoms inside GeSiAS are also demonstrated. The opened band gaps of AM covered GeSiAS range from 14.8 to 269.1 meV along with the effective masses of electrons ranging from 0.013 to 0.109 me, indicating the high tunability of band gap as well as high mobility of carriers. These results provide a development in two-dimensional alloys and show potential applications in novel micro/nano-electronic devices.

  17. Negative Thermal Expansion in Ba0.5Sr0.5Zn2SiGeO7

    Science.gov (United States)

    Thieme, Christian; Rüssel, Christian

    2016-01-01

    Solid solutions with the composition Ba0.5Sr0.5Zn2Si2-xGexO7 and BaZn2Si2-xGexO7 were prepared with different values of x using a conventional mixed oxide route. Both compounds exhibit very different thermal expansion, which is due to the different crystal structures. Ba0.5Sr0.5Zn2Si2-xGexO7 solid solutions exhibit the structure of high-temperature BaZn2Si2O7 and show negative thermal expansion, which was proven via high-temperature X-ray diffraction. Up to around x = 1, the crystal structure remains the same. Above this value, the low-temperature phase becomes stable. The Sr-free solid solutions have the crystal structure of low-temperature BaZn2Si2O7 and show also a limited solubility of Ge. These Sr-free compositions show transitions of low- to high-temperature phases, which are shifted to higher temperatures with increasing Ge-concentration. PMID:28773746

  18. Ballistic rectification in an asymmetric Si/SiGe cross junction with modulated electron density

    Energy Technology Data Exchange (ETDEWEB)

    Salloch, Daniel; Wieser, Ulrich; Kunze, Ulrich [Werkstoffe und Nanoelektronik, Ruhr-Universitaet Bochum (Germany); Hackbarth, Thomas [DaimlerChrysler Forschungszentrum Ulm (Germany)

    2010-07-01

    We demonstrate a substantial efficiency increase in an injection-type ballistic rectifier due to a modulated electron density in its active region. The rectifier is a nanoscale four-terminal {psi}-shaped cross junction fabricated from a high-mobility Si/SiGe heterostructure. Two nanoscale Schottky gates are locally deposited on top of the central stem above and below the cross junction. In addition to the inertial-ballistic rectified voltage, which will develop between the upper and lower end of the central stem if a current is injected between the branches, a hot-electron thermopower voltage establishes across the saddle-point potential formed below the local gate for negative gate-voltages. At T=4.2 K we observe an increase of the rectified signal due to the superposed hot-electron thermopower for negative gate voltages. Depending on the position of the constriction in the stem, a sign reversal of the output signal is also demonstrated. Both signals are experimentally separated in a modified device geometry.

  19. Muonium hyperfine parameters in Si{sub 1-} {sub x} Ge {sub x} alloys

    Energy Technology Data Exchange (ETDEWEB)

    King, Philip [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX (United Kingdom)]. E-mail: p.j.c.king@rl.ac.uk; Lichti, Roger [Physics Department, Texas Tech University, Lubbock, TX 79409-1051 (United States); Cottrell, Stephen [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX (United Kingdom); Yonenaga, Ichiro [Institute for Materials Research, Tohoku University (Japan)

    2006-03-31

    We present studies of muonium behaviour in bulk, Czochralski-grown Si{sub 1-} {sub x} Ge {sub x} alloy material, focusing in particular on the hyperfine parameter of the tetrahedral muonium species. In contrast to the bond-centred species, the hyperfine parameter of the tetrahedral-site muonium centre (Mu{sub T}) appears to vary non-linearly with alloy composition. The temperature dependence of the Mu{sub T} hyperfine parameter observed in low-Ge alloy material is compared with that seen in pure Si, and previous models of the Mu{sub T} behaviour in Si are discussed in the light of results from Si{sub 1-} {sub x} Ge {sub x} alloys.

  20. The giant magnetocaloric effect in Gd5Si2Ge2 with low purity gadolinium

    Institute of Scientific and Technical Information of China (English)

    ZHANG Tiebang; CHEN Yungui; FU Hao; TENG Baohua; TANG Yongbai; TU Mingjing

    2005-01-01

    The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Powder XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200℃ for 1 h had a significant magnetic- crystallographic first order phase transition at about 270 K. The maximal magnetic entropy change is 17.55 J·kg-1·K-1 under a magnetic field change of 0―5 T. The distinct increase of magnetic entropy change belongs to the first-order phase transition from the orthorhombic Gd5Si4-type to the monoclinic Gd5Si2Ge2-type after high temperature heat-treatment.

  1. Investigating the performance of SiGe embedded dual source p-FinFET architecture

    Science.gov (United States)

    Sinha, Kunal; Gupta, Partha Sarathi; Chattopadhyay, Sanatan; Rahaman, Hafizur

    2016-10-01

    In this work, a modified Fin shaped Field Effect Transistor (FinFET) structure has been proposed with dual SiGe embedded extended source regions. Comparative simulation studies with SiGe embedded source/drain conventional single Fin channel and dual Fin channel FinFET structure having similar device footprint area shows almost 3× and 1.5× improvement of drive current respectively and lower threshold voltage in the proposed architecture. The dual extended SiGe source regions and presence of Si drain in the vertical direction of the channel generate bi-axial channel stress which improves the channel charge density, which results in improvement in drive current significantly. Also it has been observed from various simulation studies that the separated gate regions increase the inversion current density in the channel which also leads to improvement of the device performance.

  2. X-ray investigation of buried SiGe islands for devices with strain-enhanced mobility

    NARCIS (Netherlands)

    Hrauda, N.; Zhang, J.J.; Stangl, J.; Rehman-Khan, A.; Bauer, G.; Stoffel, M.; Schmidt, O.G.; Jovanovich, V.; Nanver, L.K.

    2009-01-01

    In this work self-organized SiGe islands are used as stressors for Si capping layers, which later act as carrier channels in field effect transistors. To be able to address individual islands and to obtain a sufficiently narrow distribution of their properties, the SiGe islands are grown by molecula

  3. Study of Cutoff Frequency of High Collector Current Density in SiGe Single-Heterojunction Bipolar Transistor

    Directory of Open Access Journals (Sweden)

    G. M. Khanduri

    2004-01-01

    Full Text Available The cutoff frequency performance of an NPN Si/SiGe/SiGe Single-heterojunction bipolar transistor (SiGe SHBT at high collector current densities has been analyzed using a 2-dimensional MEDICI device simulator. A conventional NPN Si/SiGe/Si Double-heterojunction bipolar transistor (SiGe DHBT having uniform 14%Ge in the base region has been investigated for comparison. The analysis shows the formation of a retarding potential barrier for minority carrier electrons at the basecollector heterojunction of the DHBT structure. Whereas, the base-collector homojunction of the SiGe SHBT structure, having a uniform 14%Ge profile in its base and collector, inhibits the formation of such a retarding potential barrier. The SHBT structure with a base-collector homojunction shows an Improved cutoff frequency at a high collector current density in comparison with conventional SiGe DHBT, which makes it more promising for high speed, scaled down, field-specific applications.

  4. Mechanism of the addition of nonenolizable aldehydes and ketones to (Di)metallenes (R(2)X=YR(2), X = Si, Ge Y = C, Si, Ge): a density functional and multiconfigurational perturbation theory study.

    Science.gov (United States)

    Mosey, Nicholas J; Baines, Kim M; Woo, Tom K

    2002-11-06

    The mechanism of the addition of nonenolizable aldehydes and ketones to group 14 (di)metallenes has been examined through a theoretical study of the addition of formaldehyde to Si=C, Ge=C, Si=Si, Si=Ge, and Ge=Ge bonds at the B3LYP/6-311++G(d,p) and CAS-MCQDPT2/6-31++G(d,p) levels of theory. The reaction pathways located can be grouped as either involving the formation of singlet diradical or zwitterionic intermediates or as concerted processes. Within each group of reaction pathways, several different mechanisms have been located, with not all mechanisms being available to all of the (di)metallenes. It was found that for reactions in which a Si-O bond results (i.e., addition to Si=C, Si=Si, and Si=Ge) both diradical and zwitterionic intermediates are possible; however, the formation of diradical intermediates was not found for reactions that result in the formation of a Ge-O bond (addition to Ge=C and Ge=Ge). The underlying cause of this pathway selectivity is examined, as well as the effect of solvent on the relative energies of the pathways. The results of the study shed light on the cause of experimentally obtained results regarding the mechanism of the reaction of (di)metallenes with nonenolizable ketones and aldehydes.

  5. ‘Symbiotic’ semiconductors: unusual and counter-intuitive Ge/Si/O interactions

    Science.gov (United States)

    George, T.; Li, P. W.; Chen, K. H.; Peng, K. P.; Lai, W. T.

    2017-03-01

    Since the inception of the first transistors in the 1940s, the immense body of work on the Group IV semiconductors, Si and Ge, has spearheaded spectacular advances in modern integrated-circuit (IC) technology that has enabled a vast landscape of device applications in logic, memory, and computing. Although initially Si supplanted Ge as the material of choice for metal–oxide–semiconductor field-effect transistors, Ge-based devices are now breaking new ground. Widespread and innovative Ge-based applications exist in optoelectronics, communications, microelectro-mechanical systems, and energy harvesting/savings. On the fundamental, materials science front, while it is well known that Ge and Si are fully miscible in each other, the nature and extent of their attraction for each other has largely been unexplored. In this paper, we report a rather curious interplay between Ge and Si that occurs at high temperature (~900 °C) and that can be best described as ‘symbiotic’. Each element appears to facilitate reactions in the other which would otherwise not be possible. Oxygen intersititials also appear to play a major role in these reactions. Our experimental work has allowed us to classify four distinct regimes where these reactions occur. We describe these conditions and provide the necessary theoretical explanations for these results.

  6. Analysis of Gd5(Si2Ge2) Microstructure and Phase Transition

    Energy Technology Data Exchange (ETDEWEB)

    Meyers, John Scott [Iowa State Univ., Ames, IA (United States)

    2002-01-01

    With the recent discovery of the giant magnetocaloric effect and the beginning of extensive research on the properties of Gd5(SixGe1-x)4, a necessity has developed for a better understanding of the microstructure and crystal structure of this family of rare earth compounds with startling phenomenological properties. The aim of this research is to characterize the microstructure of the Gd5(SixGe1-x)4, with X ≅ 2 and its phase change by using both transmission and electron microscopes. A brief history of past work on Gd5(SixGe1-x)4 is necessary to understand this research in its proper context.

  7. Electronic structure of RCo{sub x}Ge{sub 2} (R=Ce,Pr,Gd) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Penc, B.; Szytula, A.; Wawrzynska, E. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland); Winiarski, A. [A. Chelkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland)

    2006-01-01

    The electronic structure of the RCo{sub x}Ge{sub 2} (R=Ce,Pr,Gd) compounds with the orthorhombic crystal structure of CeNiSi{sub 2}-type was studied by X-ray photoemission spectroscopy. The valence bands of CeCo{sub 0.86}Ge{sub 2} and PrCo{sub 0.85}Ge{sub 2} compounds have the similar character. Near the Fermi level the broad peak corresponding to the Co 3d and R 4f and 5d6s states is observed. In the case of GdCo{sub 0.64}Ge{sub 2}, the strong intensity peak at 8.7 eV corresponding to Gd 4f states is observed. The analysis of the XPS spectra of Ce and Pr 3d{sub 5/2} and 3d{sub 3/2} in the Gunnarson-Schoenhammer model give the information on the hybridization of the f orbital with the conduction band. The hybridization energy equal 93 eV for R=Ce and 143 eV for R=Pr, respectively indicate stability of the shell in these compounds. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. The Role of the Silicon Germanium (SiGe) Heterojunction Bipolar Transistor (HBT) in Mobile Technology Platforms

    Science.gov (United States)

    2011-09-01

    The Role of the Silicon Germanium (SiGe) Heterojunction Bipolar Transistor (HBT) in Mobile Technology Platforms by Gregory A. Mitchell...Germanium (SiGe) Heterojunction Bipolar Transistor (HBT) in Mobile Technology Platforms 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...MD 20783-1197 ARL-TN-0459 September 2011 The Role of the Silicon Germanium (SiGe) Heterojunction Bipolar Transistor (HBT) in Mobile

  9. One-dimensional Si/Ge nanowires and their heterostructures for multifunctional applications-a review.

    Science.gov (United States)

    Ray, Samit K; Katiyar, Ajit K; Raychaudhuri, Arup K

    2017-03-03

    Remarkable progress has been made in the field of one-dimensional semiconductor nanostructures for electronic and photonic devices. Group-IV semiconductors and their heterostructures have dominated the years of success in microelectronic industry. However their use in photonic devices is limited since they exhibit poor optical activity due to indirect band gap nature of Si and Ge. Reducing their dimensions below a characteristic length scale of various fundamental parameters like exciton Bohr radius, phonon mean free path, critical size of magnetic domains, exciton diffusion length etc result in the significant modification of bulk properties. In particular, light emission from Si/Ge nanowires due to quantum confinement, strain induced band structure modification and impurity doping may lead to the integration of photonic components with mature silicon CMOS technology in near future. Several promising applications based on Si and Ge nanowires have already been well established and studied, while others are now at the early demonstration stage. The control over various forms of energy and carrier transport through the unconstrained dimension makes Si and Ge nanowires a promising platform to manufacture advanced solid-state devices. This review presents the progress of the research with emphasis on their potential application of Si/Ge nanowires and their heterostructures for electronic, photonic, sensing and energy devices.

  10. One-dimensional Si/Ge nanowires and their heterostructures for multifunctional applications—a review

    Science.gov (United States)

    Ray, Samit K.; Katiyar, Ajit K.; Raychaudhuri, Arup K.

    2017-03-01

    Remarkable progress has been made in the field of one-dimensional semiconductor nanostructures for electronic and photonic devices. Group-IV semiconductors and their heterostructures have dominated the years of success in microelectronic industry. However their use in photonic devices is limited since they exhibit poor optical activity due to indirect band gap nature of Si and Ge. Reducing their dimensions below a characteristic length scale of various fundamental parameters like exciton Bohr radius, phonon mean free path, critical size of magnetic domains, exciton diffusion length etc result in the significant modification of bulk properties. In particular, light emission from Si/Ge nanowires due to quantum confinement, strain induced band structure modification and impurity doping may lead to the integration of photonic components with mature silicon CMOS technology in near future. Several promising applications based on Si and Ge nanowires have already been well established and studied, while others are now at the early demonstration stage. The control over various forms of energy and carrier transport through the unconstrained dimension makes Si and Ge nanowires a promising platform to manufacture advanced solid-state devices. This review presents the progress of the research with emphasis on their potential application of Si/Ge nanowires and their heterostructures for electronic, photonic, sensing and energy devices.

  11. Towards from indirect to direct band gap and optical properties of XYP{sub 2} (X=Zn, Cd; Y=Si, Ge, Sn)

    Energy Technology Data Exchange (ETDEWEB)

    Ullah, Sibghat [Department of Physics, Hazara University Mansehra, KPK (Pakistan); Murtaza, G., E-mail: murtaza@icp.edu.pk [Materials Modeling Lab, Department of Physics, Islamia College, Peshawar (Pakistan); Khenata, R. [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 Mascara (Algeria); Reshak, A.H. [New Technologies—Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Hayat, S.S. [Department of Physics, Hazara University Mansehra, KPK (Pakistan); Bin Omran, S. [Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)

    2014-05-15

    First principle calculations are performed to predict the electronic and optical properties of XYP{sub 2} (X=Zn, Cd; Y=Si, Ge, Sn) compounds. The calculations show an excellent agreement with the available experimental results as compared to previous calculations. The band gap value decreases by changing the cations X from Zn to Cd as well as Y from Si to Ge to Sn in XYP{sub 2}. The d-states of the Zn and Cd contribute majorly in the density of states. Bonding nature in these compounds is analyzed from the electron density plots. Optical response of these compounds is noted from the complex refractive index and reflectivity spectra. The wide direct band gap and the high reflectivity in the visible and ultraviolet regions for these compounds make them potential candidates for optoelectronic and photonic applications.

  12. Low-temperature growth of fully epitaxial CoFe/Ge/Fe3Si layers on Si for vertical-type semiconductor spintronic devices

    Science.gov (United States)

    Sakai, S.; Kawano, M.; Ikawa, M.; Sato, H.; Yamada, S.; Hamaya, K.

    2017-09-01

    We develop a low-temperature growth technique of epitaxial Ge layers on a body-centered-cubic ferromagnetic metal (bcc-FM), Fe3Si, by combining solid phase epitaxy (SPE) and molecular beam epitaxy (MBE). The insertion of an SPE-grown Ge layer enables two-dimensional epitaxial growth of Ge layers by MBE even at a growth temperature of ∼175 {}\\circ C. Thanks to the relatively flat surface of the Ge epilayers, we can obtain an epitaxial CoFe (bcc-FM) layer on top of the Ge layers, leading to the all-epitaxial CoFe/Ge/Fe3Si trilayer with a reasonable magnetization reversal process. We believe that the all-epitaxial CoFe/Ge/Fe3Si trilayer has great potential to be utilized as novel vertical-type Ge-channel spintronic devices.

  13. Correlation of Bandgap Reduction with Inversion Response in (Si)GeSn/High-k/Metal Stacks.

    Science.gov (United States)

    Schulte-Braucks, C; Narimani, K; Glass, S; von den Driesch, N; Hartmann, J M; Ikonic, Z; Afanas'ev, V V; Zhao, Q T; Mantl, S; Buca, D

    2017-03-15

    The bandgap tunability of (Si)GeSn group IV semiconductors opens a new era in Si-technology. Depending on the Si/Sn contents, direct and indirect bandgaps in the range of 0.4-0.8 eV can be obtained, offering a broad spectrum of both photonic and low power electronic applications. In this work, we systematically studied capacitance-voltage characteristics of high-k/metal gate stacks formed on GeSn and SiGeSn alloys with Sn-contents ranging from 0 to 14 at. % and Si-contents from 0 to 10 at. % particularly focusing on the minority carrier inversion response. A clear correlation between the Sn-induced shrinkage of the bandgap energy and enhanced minority carrier response was confirmed using temperature and frequency dependent capacitance voltage-measurements, in good agreement with k.p theory predictions and photoluminescence measurements of the analyzed epilayers as reported earlier. The enhanced minority generation rate for higher Sn-contents can be firmly linked to the bandgap reduction in the GeSn epilayer without significant influence of substrate/interface effects. It thus offers a unique possibility to analyze intrinsic defects in (Si)GeSn epilayers. The extracted dominant defect level for minority carrier inversion lies approximately 0.4 eV above the valence band edge in the studied Sn-content range (0-12.5 at. %). This finding is of critical importance since it shows that the presence of Sn by itself does not impair the minority carrier lifetime. Therefore, the continuous improvement of (Si)GeSn material quality should yield longer nonradiative recombination times which are required for the fabrication of efficient light detectors and to obtain room temperature lasing action.

  14. Photoluminescence studies of epitaxial Si 1- xGe x and Si 1- x-yGe xC y layers on Si formed by ion beam synthesis

    Science.gov (United States)

    Katsumata, H.; Kobayashi, N.; Makita, Y.; Hasegawa, M.; Hayashi, N.; Shibata, H.; Uekusa, S.

    1997-01-01

    Low temperature (2 K) photoluminescence (PL) properties of epitaxial Si 1- xGe x and Si 1- x-yGe xC y layers on Si ( x = 0.13 and y = 0.014 at peak concentration) formed by ion beam synthesis (IBS) have been investigated. Samples were prepared by a high-dose Ge with/without C ion implantation (I 2) at room temperature and by subsequent three different crystallization techniques: (i) furnace annealing (FA) process up to 840°C, (ii) ion beam-induced epitaxial crystallization (IBIEC) process with 400 keV Ge or Ar ions at 300-350°C, and (iii) IBIEC process followed by FA process up to 640°C (IBIEC + FA). Although FA-grown Si 1- x-yGe xC y samples showed G-line (C sSi iC s complex) emission at 0.969 eV, IBIEC-grown samples presented a sharp I 1 non-phonon emission at 1.0193 eV. This indicates that C atoms agglomeration is dominant for FA-grown samples, while a creation of trigonal tetravacancy cluster is dominant for IBIEC-grown samples. On the other hand, (IBIEC with Ge ions + FA)-grown Si 1- x-yGe xC y samples showed neither G-line nor I 1-related emissions, which indicates that good crystalline Si 1- x-yGe xC y layers without C agglomeration were formed by this process. In contrast, (IBIEC with Ar ions + FA)-grown samples exhibited novel successive PL vibronic sidebands at 0.98-1.03 eV. From their excitation power dependence measurements, they were found to be associated with exciton bound to defects levels created by Ar + bombardment.

  15. Comparative study of GeO2/Ge and SiO2/Si structures on anomalous charging of oxide films upon water adsorption revealed by ambient-pressure X-ray photoelectron spectroscopy

    Science.gov (United States)

    Mori, Daichi; Oka, Hiroshi; Hosoi, Takuji; Kawai, Kentaro; Morita, Mizuho; Crumlin, Ethan J.; Liu, Zhi; Watanabe, Heiji; Arima, Kenta

    2016-09-01

    The energy difference between the oxide and bulk peaks in X-ray photoelectron spectroscopy (XPS) spectra was investigated for both GeO2/Ge and SiO2/Si structures with thickness-controlled water films. This was achieved by obtaining XPS spectra at various values of relative humidity (RH) of up to ˜15%. The increase in the energy shift is more significant for thermal GeO2 on Ge than for thermal SiO2 on Si above ˜10-4% RH, which is due to the larger amount of water molecules that infiltrate into the GeO2 film to form hydroxyls. Analyzing the origins of this energy shift, we propose that the positive charging of a partially hydroxylated GeO2 film, which is unrelated to X-ray irradiation, causes the larger energy shift for GeO2/Ge than for SiO2/Si. A possible microscopic mechanism of this intrinsic positive charging is the emission of electrons from adsorbed water species in the suboxide layer of the GeO2 film to the Ge bulk, leaving immobile cations or positively charged states in the oxide. This may be related to the reported negative shift of flat band voltages in metal-oxide-semiconductor diodes with an air-exposed GeO2 layer.

  16. First principles study of crystal Si-doped Ge2Sb2Te5

    Science.gov (United States)

    Yan, Beibei; Yang, Fei; Chen, Tian; Wang, Minglei; Chang, Hong; Ke, Daoming; Dai, Yuehua

    2017-02-01

    Ge2Sb2Te5 (GST) and Si-doped GST with hexagonal structure were investigated by means of First-principles calcucations. We performed many kinds of doping types and studied the electronic properties of Si-doped GST with various Si concentrations. The theoretical calculations show that the lowest formation energy appeared when Si atoms substitute the Sb atoms (SiSb). With the increasing of Si concentrations from 10% to 30%, the impurity states arise around the Fermi level and the band gap of the SiSb structure broadens. Meanwhile, the doping supercell has the most favorable structure when the doping concentration keeps in 20%. The Si-doped GST exhibits p-type metallic characteristics more distinctly owing to the Fermi level moves toward the valence band. The Te p, d-orbitals electrons have greater impact on electronic properties than that of Te s-orbitals.

  17. Fabrication of SiGeSb heating electrodes and their application for four-terminal chalcogenide programmable switches

    Science.gov (United States)

    Park, Young Sam; Lee, Seung-Yun

    2015-03-01

    This paper reports on sputter-deposited SiGeSb thin films and their application for four-terminal chalcogenide switch devices. The microstructures and electrical properties of the SiGeSb films were highly dependent on antimony concentration and annealing temperature. Microstructural changes such as surface roughening and formation of antimony grains were observed only for the Sb-rich SiGeSb films after annealing at 400 °C and higher. The sheet resistance of the SiGeSb films containing a small amount of antimony changed sporadically with annealing temperature because of a trade-off between activation and surface depletion of antimony. The resistance of the SiGeSb heating electrodes was varied by changing sputtering power for the antimony target and by changing the annealing temperature. Four-terminal chalcogenide switch devices were fabricated with SiGeSb heating electrodes of varying resistance. It was found that the switching voltage of the fabricated switch device was proportional to the resistance of the SiGeSb heating electrode. This indicates that the SiGeSb films with tunable sheet resistance are of great importance in fabricating chalcogenide switch devices and the optimization of the resistance of the SiGeSb film is essential to ensure proper switch operation.

  18. Influence of Ge content and annealing conditions on the PL properties of nc-Si{sub 1−x}Ge{sub x} embedded in SiO{sub 2} matrix in weak quantum confined regime

    Energy Technology Data Exchange (ETDEWEB)

    Tuğay, Evrin, E-mail: evrin.tugay@erdogan.edu.tr [Department of Mechanical Engineering, Faculty of Engineering, Recep Tayyip Erdogan University, Rize 53100 (Turkey); Ilday, Serim [Department of Micro and Nanotechnology, Middle East Technical University, Ankara (Turkey); Center of Solar Energy Research and Application (GÜNAM), Middle East Technical University (METU), 06531 Ankara (Turkey); Turan, Raşit [Center of Solar Energy Research and Application (GÜNAM), Middle East Technical University (METU), 06531 Ankara (Turkey); Department of Physics, Middle East Technical University, Ankara (Turkey); Finstad, Treje G. [Department of Physics, University of Oslo, Oslo (Norway)

    2014-11-15

    Fabrication of Si (nc-Si), Ge (nc-Ge), and Si{sub 1−x}Ge{sub x} (nc-Si{sub 1−x}Ge{sub x}) nanocrystals embedded in SiO{sub 2} matrix is achieved by thermal annealing of magnetron-sputtered thin films. Effects of annealing conditions, namely duration and temperature, as well as Ge content on the photoluminescence properties are investigated. Origin and evolution of the photoluminescence signal in the weak quantum confinement regime are discussed. It is found that photoluminescence signals can be decomposed into four Gaussian peaks originating from Ge-related radiative defects located at the sub-oxide (GeO{sub x}), either inside the matrix or at the interface region (peak M), nc-Si{sub 1−x}Ge{sub x}/SiO{sub 2} interface-related localized states (peak I), localized states in the amorphous Si{sub 1−x}Ge{sub x} bandgap (peak A) and quantum confinement of excitons in small nanocrystals (peak Q). The role of small and large nanocrystals in the photoluminescence mechanism is investigated by varying the mean nanocrystal size from 3 nm to 23 nm (from strong to weak quantum confined regime). Our results demonstrate that the quantum confinement effect in Ge nanocrystals manifests though spectral blueshift due to increase in Ge content. We also propose that the decreasing photoluminescence signal intensity with an increase in Ge content may originate from Ge-related nonradiative P{sub b} centers. - Highlights: • Origin and evolution of PL in weak quantum confinement regime are investigated. • It is necessary to distinguish between the role of smaller and larger nanocrystals. • Blueshift and PL quenching by incorporation of more Ge atoms has been observed.

  19. Two-temperature synthesis of non-linear optical compound CdGeAs2

    Science.gov (United States)

    Zhu, Chongqiang; Verozubova, G. A.; Mironov, Yuri P.; Lei, Zuotao; Song, Liangcheng; Ma, Tianhui; Okunev, A. O.; Yang, Chunhui

    2016-12-01

    In this work, we report on a new approach to synthesize large-scale nonlinear optical chalcopyrite compound CdGeAs2 (cadmium germanium arsenide), in which the arsenic (As) precursor and the mixture of the cadmium (Cd) and the germanium (Ge) were separated in two distinct temperature-defined zones of a furnace. Through probing the intermediate product prepared at pre-set temperature points of hot-zone area, it was revealed that the ternary compound CdGeAs2 was formed through chemical reactions among Cd3As2, CdAs2, GeAs, GeAs2 and Ge. A new intermediate crystalline compound, with determined crystal parameter c=0.9139 nm and unknown a parameter, was identified when the temperature of the mixture of Cd and Ge was set to 680 °C, which, however, disappeared when the temperature was set to 770 °C, yielding pure CdGeAs2 product. Most likely, the identified new intermediate compound has layered graphite-like structure. Moreover, we show that the described two-temperature synthesis method allows us to produce near 250 g CdGeAs2 product during one run in a horizontal furnace and 500 g in a tilted horizontal furnace with rotated reactor.

  20. Structural and Electronic Properties of Low-Dimensional C-Nanoassemblies and Possible Analogues for Si (and Ge

    Directory of Open Access Journals (Sweden)

    N. H. March

    2011-01-01

    Full Text Available The delocalised nature of π-electrons in carbon-based compounds has opened a huge path for new fundamental and technological developments using carbon-based materials of different dimensionality (from clusters, to surfaces, nanotubes and graphene, among others. The success of this field has prompted the proposal that other inorganic structures based on B and N and more recently on Si and Ge could be formed with specific structural, mechanical, and electronic properties. In this paper we provide an analysis of the similarities of the two fields starting from the analysis of the Si6H6 molecule, the analogue of the benzene molecule but now being nonplanar. Then we move to the study of the two-dimensional (buckled analogues of graphene but now formed by Si and Ge. Similarly, we look to nonplanar compounds based on boron and boron-carbon nitrogen composites. In particular, we focus on the mechanical properties of those new materials that exhibit a very high stiffness, resilience, and flexibility. Possible applications in the fields of catalysis, lubrication, electronic, and photonic devices now seem a likely by-product. We also address future directions triggered by the predicted superconducting properties of graphene, among other areas.

  1. Relationship between structural changes, hydrogen content and annealing in stacks of ultrathin Si/Ge amorphous layers

    Directory of Open Access Journals (Sweden)

    Boyen Hans-Gerd

    2011-01-01

    Full Text Available Abstract Hydrogenated multilayers (MLs of a-Si/a-Ge have been analysed to establish the reasons of H release during annealing that has been seen to bring about structural modifications even up to well-detectable surface degradation. Analyses carried out on single layers of a-Si and a-Ge show that H is released from its bond to the host lattice atom and that it escapes from the layer much more efficiently in a-Ge than in a-Si because of the smaller binding energy of the H-Ge bond and probably of a greater weakness of the Ge lattice. This should support the previous hypothesis that the structural degradation of a-Si/a-Ge MLs primary starts with the formation of H bubbles in the Ge layers.

  2. Monoclinic 122-Type BaIr2Ge2 with a Channel Framework: A Structural Connection between Clathrate and Layered Compounds

    Directory of Open Access Journals (Sweden)

    Xin Gui

    2017-07-01

    Full Text Available A new 122-type phase, monoclinic BaIr2Ge2 is successfully synthesized by arc melting; X-ray diffraction and scanning electron microscopy are used to purify the phase and determine its crystal structure. BaIr2Ge2 adopts a clathrate-like channel framework structure of the monoclinic BaRh2Si2-type, with space group P21/c. Structural comparisons of clathrate, ThCr2Si2, CaBe2Ge2, and BaRh2Si2 structure types indicate that BaIr2Ge2 can be considered as an intermediate between clathrate and layered compounds. Magnetic measurements show it to be diamagnetic and non-superconducting down to 1.8 K. Different from many layered or clathrate compounds, monoclinic BaIr2Ge2 displays a metallic resistivity. Electronic structure calculations performed for BaIr2Ge2 support its observed structural stability and physical properties.

  3. Structural, elastic, electronic, bonding, and optical properties of BeAZ{sub 2} (A = Si, Ge, Sn; Z = P, As) chalcopyrites

    Energy Technology Data Exchange (ETDEWEB)

    Fahad, Shah [Department of Physics, Hazara University Mansehra, KPK, Mansehra (Pakistan); Murtaza, G., E-mail: murtaza@icp.edu.pk [Materials Modeling Laboratory, Department of Physics, Islamia College University, Peshawar (Pakistan); Ouahrani, T. [Laboratoire de Physique Théorique, B.P. 230, Université de Tlemcen, Tlemcen 13000 (Algeria); Ecole Préparatoire en Sciences et Techniques, BP 165 R.P., 13000 Tlemcen (Algeria); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 (Algeria); Yousaf, Masood [Center for Multidimensional Carbon Materials, Institute for Basic Science, Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 689-798 (Korea, Republic of); Omran, S.Bin [Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Mohammad, Saleh [Department of Physics, Hazara University Mansehra, KPK, Mansehra (Pakistan)

    2015-10-15

    A first principles density functional theory (DFT) technique is used to study the structural, chemical bonding, electronic and optical properties of BeAZ{sub 2} (A = Si, Ge, Sn; Z = P, As) chalcopyrite materials. The calculated parameters are in good agreement with the available experimental results. The lattice constants and the equilibrium volume increased as we moved from Si to Ge to Sn, whereas the c/a and internal parameters u decreased by shifting the cation from P to As. These compounds are elastically stable. An investigation of the band gap using the WC-GGA, EV-GGA, PBE-GGA and mBJ-metaGGA potentials suggested that BeSiP{sub 2} and BeSiAs{sub 2} are direct band gap compounds, whereas BeGeP{sub 2,} BeGeAs{sub 2,} BeSnP{sub 2,} BeSnAs{sub 2} are indirect band gap compounds. The energy band gaps decreased by changing B from Si to Sn and increased by changing the anion C from P to As. The bonding among the cations and anions is primarily ionic. In the optical properties, the real and imaginary parts of the dielectric functions, reflectivity and optical conductivity have been studied over a wide energy range. - Highlights: • The compounds are studied by FP-LAPW method within mBJ approximation. • All of the studied materials show isotropic behaviour. • All the compounds show direct band gap nature. • Bonding nature is mostly covalent among the studied compounds. • High absorption peaks and reflectivity ensures there utility in optoelectronic devices.

  4. Fabrication of GaAs quantum dots by droplet epitaxy on Si/Ge virtual substrate

    Energy Technology Data Exchange (ETDEWEB)

    Bietti, S; Sanguinetti, S; Somaschini, C; Koguchi, N [L-NESS and Dipartimento di Scienza dei Materiali dell' Universita degli Studi di Milano-Bicocca, Via Cozzi 53, I-20125 Milano (Italy); Isella, G; Chrastina, D; Fedorov, A, E-mail: sergio.bietti@mater.unimib.it [CNISM, L-NESS and Dipartimento di Fisica del Politecnico di Milano, Via Anzani 42, Como (Italy)

    2009-11-15

    We present here the fabrication, via droplet epitaxy, of GaAs/AlGaAs quantum dots with high optical efficiency on Si. The growth substrate lattice parameter was adapted to that of (Al)GaAs via Ge virtual substrates (GeVS). The samples clearly show the presence of quantum dot self-assembly, with the designed shape and density. Photoluminescence measurements, performed at low temperature, show an intense emission band from the quantum dots.

  5. First-principles study of new series of quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb)

    Energy Technology Data Exchange (ETDEWEB)

    Bouabça, A. [Condensed Matter and Sustainable Development Laboratory (LMCDD), University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria); Rozale, H., E-mail: hrozale@yahoo.fr [Condensed Matter and Sustainable Development Laboratory (LMCDD), University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria); Amar, A. [Condensed Matter and Sustainable Development Laboratory (LMCDD), University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria); Wang, X.T. [School of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 400044 (China); Sayade, A. [UCCS, CNRS-UMR 8181, Université d’Artois, Faculté des Sciences Jean Perrin, Rue Jean Souvraz, SP 18, 62307 Lens Cedex (France); Chahed, A. [Condensed Matter and Sustainable Development Laboratory (LMCDD), University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria)

    2016-12-01

    The structural, electronic, magnetic, and thermal properties of new quaternary Heusler alloys CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb) were investigated using the full-potential linearized augmented plane wave (FPLAPW) within the generalized gradient approximation (GGA) and GGA plus modified Becke and Johnson as the exchange correlation. The results showed that all Heusler compounds were stable in Type (I) structure. The CsSrCZ (Z=Si, Ge, Sn) compounds had a nearly HM characteristic, and CsSrCZ (Z=P, As, Sb) compounds were true half-metallic (HM) ferromagnets. The strong spin polarization of p orbital for C, Si, Ge, Sn, P, As, and Sb atoms is found to be the origin of ferromagnetic. The half-metallicity is preserved up to a lattice contraction of 3.45%, 1.69%, 1.69%, 7.16%, 7.16%, and 11.2% for all six quaternary Heusler compounds. We also investigated the thermal effects using the quasi-harmonic Debye model. - Highlights: • Electronic, magnetic, and thermodynamic properties of CsSrCZ (Z=Si, Ge, Sn, P, As, and Sb) are investigated. • Until now, there have been no reports theoretical and experimental studies on d{sup 0} half-metals with quaternary structures. • The strong spin polarization of p orbital for C, Si, Ge, Sn, P, As, and Sb atoms is found to be the origin of ferromagnetic. • The half-metallicity is preserved up to a lattice contraction.

  6. Finite elements analysis of heteroepitaxial SiGe layers grown by excimer laser

    Science.gov (United States)

    Conde, J. C.; González, P.; Lusquiños, F.; Chiussi, S.; Serra, J.; León, B.

    2005-07-01

    In this work, the finite elements analysis using ANSYS ® (8.0) of the heteroepitaxial SiGe alloy formation induced by excimer lasers is presented. The numerical simulation of the temperature distribution induced by KrF excimer laser (energy densities 0.50 substrates is obtained. An acceptable agreement between the numerical simulations and the experimental results is found. The melting depth is also evaluated and the laser energy density threshold for the partial melting of the Si substrate is estimated. It allows us to determine the optimum conditions to achieve high quality epitaxy. For both the cases, the temperature profile versus time on the top of the Ge film and at the Ge/Si interface are obtained.

  7. Segregation, quantum confinement effect and band offset for [110] SiGe NWs

    Energy Technology Data Exchange (ETDEWEB)

    Amato, Michele [CNR-Istituto di Nanoscienze, Modena (Italy); Dipartimento di Fisica, Universita' di Modena e Reggio Emilia, Modena (Italy); Palummo, Maurizia [European Theoretical Spectroscopy Facility (ETSF), CNR-INFM-SMC, Roma (Italy); Dipartimento di Fisica, Universita di Roma, ' Tor Vergata' , Roma (Italy); Ossicini, Stefano [European Theoretical Spectroscopy Facility (ETSF), CNR-Istituto di Nanoscienze ' ' Centro S3' ' , Reggio Emilia (Italy); Dipartimento di Scienze e Metodi dell' Ingegneria, e Centro Interdipartimentale ' ' En and Tech' ' , Universita di Modena e Reggio Emilia, Reggio Emilia (Italy)

    2010-08-15

    Results of first-principles DFT simulations provide strong evidence that, at zero temperature, for [110] oriented SiGe nanowires (NWs), the segregated structure is favoured with respect to the mixed ones; for this observation two different schemes of calculations are presented and discussed. Moreover the segregation strongly influences the NWs electronic properties, inducing a reduced quantum confined effect (RQCE). We show here that it depends on the effect of strain in the plane normal to the direction of growth and not on the choice of lattice parameter in the direction of growth. A qualitative evaluation of the band offset between Si and Ge for SiGe NWs is also presented. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  8. Ge-doped SiO{sub 2} thin films produced by helicon activated reactive evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Li, W.T.; Bulla, D.A.P.; Charles, C.; Boswell, R.; Love, J.; Luther-Davies, B

    2002-11-01

    Ge-doped SiO{sub 2} thin films for optical waveguide application were produced at low temperature by using an improved helicon plasma assisted reactive evaporation technique. Pure Si and Ge materials were simultaneously evaporated from two separated crucibles by using e-beams into high-density oxygen plasma to form the oxide films on a substrate. The film density was enhanced by supplying an r.f. bias to the substrate. Nearly H-free Ge-doped SiO{sub 2} thin films with very high atomic density ({approx}0.66x10{sup 23} cm{sup -3}), good adhesion and very low surface roughness were produced. The influence of deposition conditions, mainly the helicon r.f. power and substrate bias, on the properties of the films was studied by using surface profilometer, ellipsometer, atomic force microscope, Rutherford backscattering spectrometry, Fourier transform infrared spectrometry, and field emission scanning electron microscope.

  9. Giant magnetocaloric effect in Gd5(Si2Ge2 alloy with low purity Gd

    Directory of Open Access Journals (Sweden)

    Cleber Santiago Alves

    2004-12-01

    Full Text Available Gd5(Ge1-xSi x, x < 4 based alloys are potential candidates for magnetic refrigeration in the range ~20 - ~290 K. However, one of the greatest obstacles for the use of that technology in large scale is the utilization of high pure Gd metal (99.99 wt. (% to produce the GdGeSi alloys, since the impurity elements decrease the intensity of the magnetocaloric effect (EMC¹. In this work, we prove that annealing of the Gd5Ge2Si2 can promote remarkable values for the EMC in comparison to those obtained for the alloy with high pure Gd. Also, the as cast alloy and the annealed alloy are not monophasic, but have at least two crystalline phases in their microstructure. Results for X-ray analysis, optical and electronic microscopy and magnetization measurements are reported.

  10. Quantization and anomalous structures in the conductance of Si/SiGe quantum point contacts

    Science.gov (United States)

    von Pock, J. F.; Salloch, D.; Qiao, G.; Wieser, U.; Hackbarth, T.; Kunze, U.

    2016-04-01

    Quantum point contacts (QPCs) are fabricated on modulation-doped Si/SiGe heterostructures and ballistic transport is studied at low temperatures. We observe quantized conductance with subband separations up to 4 meV and anomalies in the first conductance plateau at 4e2/h. At a temperature of T = 22 mK in the linear transport regime, a weak anomalous kink structure arises close to 0.5(4e2/h), which develops into a distinct plateau-like structure as temperature is raised up to T = 4 K. Under magnetic field parallel to the wire up to B = 14 T, the anomaly evolves into the Zeeman spin-split level at 0.5(4e2/h), resembling the "0.7 anomaly" in GaAs/AlGaAs QPCs. Additionally, a zero-bias anomaly (ZBA) is observed in nonlinear transport spectroscopy. At T = 22 mK, a parallel magnetic field splits the ZBA peak up into two peaks. At B = 0, elevated temperatures lead to similar splitting, which differs from the behavior of ZBAs in GaAs/AlGaAs QPCs. Under finite dc bias, the differential resistance exhibits additional plateaus approximately at 0.8(4e2/h) and 0.2(4e2/h) known as "0.85 anomaly" and "0.25 anomaly" in GaAs/AlGaAs QPCs. Unlike the first regular plateau at 4e2/h, the 0.2(4e2/h) plateau is insensitive to dc bias voltage up to at least VDS = 80 mV, in-plane magnetic fields up to B = 15 T, and to elevated temperatures up to T = 25 K. We interpret this effect as due to pinching off one of the reservoirs close to the QPC. We do not see any indication of lifting of the valley degeneracy in our samples.

  11. Light harvesting with Ge quantum dots embedded in SiO{sub 2} or Si{sub 3}N{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Cosentino, Salvatore, E-mail: Salvatore.cosentino@ct.infn.it; Raciti, Rosario; Simone, Francesca; Crupi, Isodiana; Terrasi, Antonio; Mirabella, Salvo [MATIS IMM-CNR and Dipartimento di Fisica e Astronomia, Università di Catania, via S. Sofia 64, 95123 Catania (Italy); Sungur Ozen, Emel; Aydinli, Atilla [Department of Physics, Bilkent University, 06800 Ankara (Turkey); Mio, Antonio M.; Nicotra, Giuseppe [IMM-CNR, VII strada 5, 95121 Catania (Italy); Turan, Rasit [Department of Physics, Middle East Technical University, 06531 Ankara (Turkey)

    2014-01-28

    Germanium quantum dots (QDs) embedded in SiO{sub 2} or in Si{sub 3}N{sub 4} have been studied for light harvesting purposes. SiGeO or SiGeN thin films, produced by plasma enhanced chemical vapor deposition, have been annealed up to 850 °C to induce Ge QD precipitation in Si based matrices. By varying the Ge content, the QD diameter can be tuned in the 3–9 nm range in the SiO{sub 2} matrix, or in the 1–2 nm range in the Si{sub 3}N{sub 4} matrix, as measured by transmission electron microscopy. Thus, Si{sub 3}N{sub 4} matrix hosts Ge QDs at higher density and more closely spaced than SiO{sub 2} matrix. Raman spectroscopy revealed a higher threshold for amorphous-to-crystalline transition for Ge QDs embedded in Si{sub 3}N{sub 4} matrix in comparison with those in the SiO{sub 2} host. Light absorption by Ge QDs is shown to be more effective in Si{sub 3}N{sub 4} matrix, due to the optical bandgap (0.9–1.6 eV) being lower than in SiO{sub 2} matrix (1.2–2.2 eV). Significant photoresponse with a large measured internal quantum efficiency has been observed for Ge QDs in Si{sub 3}N{sub 4} matrix when they are used as a sensitive layer in a photodetector device. These data will be presented and discussed, opening new routes for application of Ge QDs in light harvesting devices.

  12. Embedded Ge nanocrystals in SiO{sub 2} synthesized by ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Baranwal, V., E-mail: vikasphy@gmail.com; Pandey, Avinash C. [Nanotechnology Application Centre, University of Allahabad, Allahabad 211 002 (India); Gerlach, J. W.; Lotnyk, A.; Rauschenbach, B. [Leibniz-Institut für Oberflächenmodifizierung, Permoserstraße 15, D-04318 Leipzig (Germany); Karl, H. [Institut für Physik, Universität Augsburg, D-86135 Augsburg (Germany); Ojha, S.; Avasthi, D. K.; Kanjilal, D. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2015-10-07

    200 nm thick SiO{sub 2} layers grown on Si substrates were implanted with 150 keV Ge ions at three different fluences. As-implanted samples were characterized with time-of-flight secondary ion mass spectrometry and Rutherford backscattering spectrometry to obtain depth profiles and concentration of Ge ions. As-implanted samples were annealed at 950 °C for 30 min. Crystalline quality of pristine, as-implanted, and annealed samples was investigated using Raman scattering measurements and the results were compared. Crystalline structure of as-implanted and annealed samples of embedded Ge into SiO{sub 2} matrix was studied using x-ray diffraction. No secondary phase or alloy formation of Ge was detected with x-ray diffraction or Raman measurements. Scanning transmission electron microscope measurements were done to get the nanocrystal size and localized information. The results confirmed that fluence dependent Ge nanocrystals of different sizes are formed in the annealed samples. It is also observed that Ge is slowly diffusing deeper into the substrate with annealing.

  13. Modal Contributions to Heat Conduction across Crystalline and Amorphous Si/Ge Interfaces

    Science.gov (United States)

    Gordiz, Kiarash; Henry, Asegun

    Until now, our entire understanding of interfacial heat transfer has been based on the phonon gas model and Landauer formalism. Based on this framework, it is difficult to offer any intuition on heat transfer between two solid materials if one side of the interface is an amorphous structure. Here, using the interface conductance modal analysis (ICMA) method, we investigate the modal contributions to thermal interface conductance (TIC) through crystalline (c) and amorphous (a) Si/Ge interfaces. It is revealed that around 15% of the conductance through the cSi/cGe interface arises from less than 0.1% of the modes of vibration in the structure that exist between 12-13THz and because of their large eigenvectors around the interface are classified as interfacial modes. Correlation maps show that these interfacial modes exhibit strong correlations with all the other modes. The physics behind this strong coupling ability is studied by calculating the mode-level harmonic and anharmonic energy distribution among all the atoms in the system. It is found that these interfacial modes are enabled by the large degree of anharmonicity near the interface, which is higher than the bulk and ultimately allows this small group of modes to couple to other modes of vibration. In addition, unlike the cSi/cGe, correlation maps for aSi/cGe, cSi/aGe, and aSi/aGe interfaces show that the majority of contributions to TIC arise from auto-correlations instead of cross-correlations. The provided analysis sheds light on the nature of localized vibrations at interfaces and can be enlightening for other investigations of localization.

  14. Electronic structure of O-doped SiGe calculated by DFT + U method

    Science.gov (United States)

    Zhao, Zong-Yan; Yang, Wen; Yang, Pei-Zhi

    2016-12-01

    To more in depth understand the doping effects of oxygen on SiGe alloys, both the micro-structure and properties of O-doped SiGe (including: bulk, (001) surface, and (110) surface) are calculated by DFT + U method in the present work. The calculated results are as follows. (i) The (110) surface is the main exposing surface of SiGe, in which O impurity prefers to occupy the surface vacancy sites. (ii) For O interstitial doping on SiGe (110) surface, the existences of energy states caused by O doping in the band gap not only enhance the infrared light absorption, but also improve the behaviors of photo-generated carriers. (iii) The finding about decreased surface work function of O-doped SiGe (110) surface can confirm previous experimental observations. (iv) In all cases, O doing mainly induces the electronic structures near the band gap to vary, but is not directly involved in these variations. Therefore, these findings in the present work not only can provide further explanation and analysis for the corresponding underlying mechanism for some of the experimental findings reported in the literature, but also conduce to the development of μc-SiGe-based solar cells in the future. Project supported by the Natural Science Foundation of Yunnan Province, China (Grant No. 2015FB123), the 18th Yunnan Province Young Academic and Technical Leaders Reserve Talent Project, China (Grant No. 2015HB015), and the National Natural Science Foundation of China (Grant No. U1037604).

  15. SiGe superlattice nanocrystal infrared and Raman spectra: A density functional theory study

    Science.gov (United States)

    Abdulsattar, Mudar A.

    2012-02-01

    Infrared and Raman vibrational spectrum are calculated using ab initio density functional theory for SiGe superlattice nanocrystal of approximately 1.6 nm length. After obtaining the optimum positions of atoms via geometrical optimization using density functional theory, coupled perturbed Hartree-Fock equations are solved iteratively to obtain vibrational spectrum. Frequencies of vibrations are analyzed against intensities, reduced masses, and vibrational force constants. A scale factor of 0.81 is suggested to correct the frequencies of the present calculations that are obtained using STO-3 G basis functions. Results show that SiGe nanocrystals have complex and rich vibrational spectrum that can be generally divided into three regions. The highest reduced masses are in the first region where Si and Ge atoms are the main contributors to vibrations with a smaller number of vibrations attributed to hydrogen atoms. The highest intensity lines in SiGe superlattice nanocrystals are in the middle region where most of the modes of vibration can be excited. The third region is characterized by high force constants. The first region shows a redshift of the original Ge-Si bond vibration from the calculated bulk 418 cm-1 to the present nanocrystal 395 cm-1. Hydrogen vibrations interferences are found in the same redshift region that might induce uncertainties in the experimentally measured redshift. Si-H and Ge-H vibrations are observed mainly in the second and third region and less frequently in the first region. These vibrations include modes of vibration such as symmetric, asymmetric, wagging, scissor, rocking, and twisting modes.

  16. Epitaxial Technologies for SiGeSn High Performance Optoelectronic Devices

    Science.gov (United States)

    2015-04-29

    a) (b) (c) Fig. 24 (a) Schematic cross -section of a GeSn/Si APD with a SACM structure and its internal electric field distribution. (b...shrinkage has been observed in heavily doped n-type samples. GeSn samples have been fabricated into photoconductive detectors, avalanche photo diodes , and...light-emitting diodes (LEDs) and in-depth study has been conducted. The responsivity of 1.63 A/W at 1.55 μm has been achieved with a Ge0.9Sn0.1

  17. Temperature-dependent electroluminescence from GeSn heterojunction light-emitting diode on Si substrate

    Science.gov (United States)

    Chang, Chiao; Li, Hui; Huang, Ssu-Hsuan; Lin, Li-Chien; Cheng, Hung-Hsiang

    2016-04-01

    The electroluminescence from a Ge/GeSn/Ge p-i-n light-emitting diode on Si was investigated under different temperatures ranging from 25 to 150 K. The diode was operated at a low injection current density of 13 A/cm2. We obtained no-phonon- and phonon-assisted replicas in emission spectra. Also, the relationship between indirect bandgap energy and temperature was investigated. The temperature-dependent bandgap energy followed Varshni’s empirical expression with α = 4.884 × 10-4 eV/K and β = 130 K.

  18. Calculation of band edge levels of strained Si/(111)Si{sup 1-x}Ge{sup x}

    Energy Technology Data Exchange (ETDEWEB)

    Song Jianjun; Zhang Heming; Hu Huiyong; Dai Xianying; Xuan Rongxi, E-mail: wmshhsong@tom.co [Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China)

    2010-01-15

    Calculations were performed on the band edge levels of (111)-biaxially strained Si on relaxed Si{sup 1-x}Ge{sup x} alloy using the k {center_dot} p perturbation method coupled with deformation potential theory. The results show that the conduction band (CB) edge is characterized by six identical valleys, that the valence band (VB) edge degeneracies are partially lifted, and that both the CB and VB edge levels move up in electron energy as the Ge fraction (x) increases. In addition, the dependence of the indirect bandgap and the VB edge splitting energy on x was obtained. Quantitative data from the results supply valuable references for Si-based strained device design. (semiconductor physics)

  19. $^{31}$Si Self-Diffusion in Si-Ge Alloys and Si-(B-)C-N Ceramics and Diffusion Studies for Al and Si Beam Developments

    CERN Multimedia

    Nylandsted larsen, A; Voss, T L; Strohm, A

    2002-01-01

    An invaluable method for studying diffusion in solids is the radiotracer technique. However, its applicability had been restricted to radiotracer atoms with half-lives $t_{1/2}$ of about 1~d or longer. Within the framework of IS372 a facility was developed in which short-lived radiotracer atoms ( 5min $\\scriptstyle{\\lesssim}$ $t_{1/2}\\scriptstyle{\\lesssim}$1 d ) can be used. For the implantation of the short-lived tracers the facility is flanged to the ISOLDE beamline, and all post-implantation steps required in the radiotracer technique are done in situ.\\\\ After successful application of this novel technique in diffusion studies of $^{11}$C ($t_{1/2}$ = 20.3 min), this experiment aims at performing self-diffusion studies of $^{31}$Si ($t_{1/2}$ = 2.6~h) in Si--Ge alloys and in amorphous Si--(B--)C--N ceramics.\\\\ Our motivation for measuring diffusion in Si--Ge alloys is their recent technological renaissance as well as the purpose to test the prediction that in these alloys the self-diffusion mechanism chang...

  20. Gas source molecular beam epitaxy and thermal stability of Si{sub 1-x} Ge{sub x}/Si superlattice materials

    Energy Technology Data Exchange (ETDEWEB)

    Zou, L.F.; Acosta-Ortiz, S.E. [Centro de Investigaciones en Optica A.C. Unidad Aguascalientes. Juan de Montoro No. 207. Zona Centro, 20000 Aguascalientes (Mexico); Zou, L.X. [Computer Science Department, Zhongnan University for Nationalities Wuhan, Hubei 430074 (China); Regalado, L.E. [Centro de Investigaciones en Optica, Loma del Bosque No. 115, Loma del Campestre C.P. 37000, Leon, Guanajuato (Mexico); Sun, D.Z.; Wang, Z.G. [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    1998-12-31

    Gas source molecular beam epitaxy has been used to grow Si{sub 1-x} Ge{sub x} alloys and Si{sub 1-x} Ge{sub x}/Si multi-quantum wells (MQWs) on (100) Si substrates with Si{sub 2}H{sub 6} and GeH{sub 4} as sources. Heterostructures and MQWs with mirror-like surface morphology, good crystalline quality, and abrupt interfaces have been studied by a variety of in situ and ex situ techniques. The structural stability and strain relaxation in Si{sub 1-x} Ge{sub x}/ Si heterostructures have been investigated, and compared to that in the As ion-implanted Si{sub 1-x} Ge{sub x} epilayers. The results show that the strain relaxation mechanism of the non-implanted Si{sub 1-x} Ge{sub x} epilayers is different form that of the As ion-implanted Si{sub 1-x} Ge{sub x} epilayers. (Author)

  1. Analysis and Design of Wide-Band SiGe HBT Active Mixers

    DEFF Research Database (Denmark)

    Johansen, Tom Keinicke; Krozer, Viktor; Vidkjær, Jens

    2005-01-01

    performing frequency conversion of wide-band signals is discussed. The analysis is verified by computer simulations using a realistic high-frequency large-signal SiGe HBT model. An active mixer design based on the Gilbert cell topology modified for wide-band operation using emitter degenerated...... transconductance stage and shunt feedback load stage is discussed. Experimental results are given for an active mixer implemented in a 0.8-μm 35-GHz fT SiGe HBT BiCMOS process....

  2. Resonant normal-incidence separate-absorption-charge-multiplication Ge/Si avalanche photodiodes.

    Science.gov (United States)

    Dai, Daoxin; Chen, Hui-Wen; Bowers, John E; Kang, Yimin; Morse, Mike; Paniccia, Mario J

    2009-09-14

    In this work the impedance of separate-absorption-charge-multiplication Ge/Si avalanche photodiodes (APD) is characterized over a large range of bias voltage. An equivalent circuit with an inductive element is presented for modeling the Ge/Si APD. All the parameters for the elements included in the equivalent circuit are extracted by fitting the measured S(22) with the genetic algorithm optimization. Due to a resonance in the avalanche region, the frequency response of the APD has a peak enhancement when the bias voltage is relatively high, which is observed in the measurement and agrees with the theoretical calculation shown in this paper.

  3. First Insertions of Carbene Ligands into Ge-N and Si-N Bonds.

    Science.gov (United States)

    Álvarez-Rodríguez, Lucía; Cabeza, Javier A; García-Álvarez, Pablo; Gómez-Gallego, Mar; Merinero, Alba D; Sierra, Miguel A

    2017-02-22

    The insertion of carbene ligands into Ge-N (three examples) and Si-N (one example) bonds has been achieved for the first time by treating Fischer carbene complexes (M = W, Cr) with bulky amidinatotetrylenes (E = Ge, Si). These reactions, which start with a nucleophilic attack of the amidinatotetrylene heavier group-14 atom to the carbene C atom, proceed through a stereoselective insertion of the carbene fragment into an E-N bond of the amidinatotetrylene ENCN four-membered ring, leading to [M(CO)5L] derivatives in which L belongs to a novel family of tetrylene ligands comprising an ECNCN five-membered ring.

  4. Quantum confinement effect in Si/Ge core-shell nanowires: First-principles calculations

    Science.gov (United States)

    Yang, Li; Musin, Ryza N.; Wang, Xiao-Qian; Chou, M. Y.

    2008-05-01

    The electronic structure of Si/Ge core-shell nanowires along the [110] and [111] directions are studied with first-principles calculations. We identify the near-gap electronic states that are spatially separated within the core or the shell region, making it possible for a dopant to generate carriers in a different region. The confinement energies of these core and shell states provide an operational definition of the “band offset,” which is not only size dependent but also component dependent. The optimal doping strategy in Si/Ge core-shell nanowires is proposed based on these energy results.

  5. Investigation of Coulomb scattering on sSi/Si0.5Ge0.5/sSOI quantum-well p-MOSFETs

    Science.gov (United States)

    Jiao, Wen; Qiang, Liu; Chang, Liu; Yize, Wang; Bo, Zhang; Zhongying, Xue; Zengfeng, Di; Wenjie, Yu; Qingtai, Zhao

    2016-09-01

    sSi/Si0.5Ge0.5/sSOI quantum-well (QW) p-MOSFETs with HfO2/TiN gate stack were fabricated and characterized. According to the low temperature experimental results, carrier mobility of the strained Si0.5Ge0.5 QW p-MOSFET was mainly governed by phonon scattering from 300 to 150 K and Coulomb scattering below 150 K, respectively. Coulomb scattering was intensified by the accumulated inversion charges in the Si cap layer of this Si/SiGe heterostructure, which led to a degradation of carrier mobility in the SiGe channel, especially at low temperature. Project supported by the National Natural Science Foundation of China (Nos. 61306126, 61306127, 61106015) and the CAS International Collaboration and Innovation Program on High Mobility Materials Engineering.

  6. C-V and DLTS Characterization of Rapid Thermal Oxides on Si0.887Ge0.113 and Si0.8811Ge0.113C0.0059 Alloys

    Science.gov (United States)

    Feng, W.; Choi, W. K.; Bera, L. K.; Mi, J.; YANG, C. Y.

    Capacitance versus voltage (C-V) and deep level transient spectroscopy (DLTS) characterization was performed on rapid thermal oxides (RTO) on Si0.887Ge0.113 and Si0.8811Ge0.113C0.0059 alloys. A high interface trap density (~ 1012 eV-1 cm-2) and a high apparent doping level were obtained for the SiO2/Si0.8811Ge0.113C0.0059 samples. The C-V results at different temperatures showed that the high apparent doping levels of the SiO2/Si0.8811Ge0.113C0.0059 samples might be due to the formation of SiC-related defects introduced by the high temperature oxidation process.

  7. Kinetics of Si and Ge nanowires growth through electron beam evaporation

    Directory of Open Access Journals (Sweden)

    Artoni Pietro

    2011-01-01

    Full Text Available Abstract Si and Ge have the same crystalline structure, and although Si-Au and Ge-Au binary alloys are thermodynamically similar (same phase diagram, with the eutectic temperature of about 360°C, in this study, it is proved that Si and Ge nanowires (NWs growth by electron beam evaporation occurs in very different temperature ranges and fluence regimes. In particular, it is demonstrated that Ge growth occurs just above the eutectic temperature, while Si NWs growth occurs at temperature higher than the eutectic temperature, at about 450°C. Moreover, Si NWs growth requires a higher evaporated fluence before the NWs become to be visible. These differences arise in the different kinetics behaviors of these systems. The authors investigate the microscopic growth mechanisms elucidating the contribution of the adatoms diffusion as a function of the evaporated atoms direct impingement, demonstrating that adatoms play a key role in physical vapor deposition (PVD NWs growth. The concept of incubation fluence, which is necessary for an interpretation of NWs growth in PVD growth conditions, is highlighted.

  8. Sn-enriched Ge/GeSn nanostructures grown by MBE on (001) GaAs and Si wafers

    Energy Technology Data Exchange (ETDEWEB)

    Sadofyev, Yu. G., E-mail: sadofyev@hotmail.com; Martovitsky, V. P.; Klekovkin, A. V. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Saraykin, V. V. [Lukin Research Institute of Physical Problems (Russian Federation); Vasil’evskii, I. S. [National Research Nuclear University MEPhI (Russian Federation)

    2015-12-15

    Elastically stressed metastable GeSn layers with a tin molar fraction as large as 0.185 are grown on (001) Si and GaAs wafers covered with a germanium buffer layer. A set of wafers with a deviation angle in the range 0°–10° is used. It is established that the GeSn crystal undergoes monoclinic deformation with the angle β to 88° in addition to tetragonal deformation. Misorientation of the wafers surface results in increasing efficiency of the incorporation of tin adatoms into the GeSn crystal lattice. Phase separation in the solid solution upon postgrowth annealing of the structures begins long before the termination of plastic relaxation of elastic heteroepitaxial stresses. Tin released as a result of GeSn decomposition predominantly tends to be found on the surface of the sample. Manifestations of the brittle–plastic mechanism of the relaxation of stresses resulting in the occurrence of microcracks in the subsurface region of the structures under investigation are found.

  9. Mazes and meso-islands: Impact of Ag preadsorption on Ge growth on Si(111)

    Science.gov (United States)

    Schmidt, Th.; Speckmann, M.; Flege, J. I.; Müller-Caspary, K.; Heidmann, I.; Kubelka-Lange, A.; Menteş, T. O.; Niño, M. Á.; Locatelli, A.; Rosenauer, A.; Falta, J.

    2016-12-01

    The preadsorption of Ag on Si(111) drastically changes the growth of Ge. In a temperature range from 400°C to 650°C, Ag adsorption on Si leads to the formation of a √{3 }×√{3 } -R 30° reconstruction that exhibits a maze-like morphology on the mesoscopic scale, as observed by low-energy electron diffraction (LEED) and low-energy electron microscopy. This maze morphology can be attributed to a surface roughening on an atomic scale, induced by the re-arrangement of top layer atoms during the 7 ×7 to √{3 }×√{3 } -R 30° transition. The subsequent deposition of Ge results in the formation of a wetting layer, the evolution of which has been found to be governed by the Ag/Si(111)-√{3 }×√{3 } -R 30° template's maze structure, as the latter offers a high density of heterogeneous nucleation sites. Upon further Ge growth, three-dimensional islands with diameters in the micrometer range are formed, which exhibit a large and flat (111) top facet. X-ray photoemission electron microscopy reveals that during Ge growth, Ag is segregating to the surface very efficiently. Grazing-incidence x-ray diffraction and transmission electron microscopy have been used to study the composition, strain state and defect structure of the Ge islands in dependence of the growth temperature. The strain induced by lattice mismatch is found to be largely relaxed (80-90% relaxation) in the investigated growth temperature range from 400 to 600°C, which is confirmed by high-resolution LEED measurements. As a main relaxation mechanism, the formation of interfacial misfit dislocations has been identified. Interdiffusion of Si into the Ge islands becomes more and more pronounced for increasing growth temperature, whereas the formation of twinned Ge regions can drastically be suppressed at higher temperature.

  10. Ion-bombardment induced morphology change of device related SiGe multilayer heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Hofer, C., E-mail: Christian.Hofer@unileoben.ac.at [Institute of Physics, Montanuniversitaet Leoben, Franz Josef Str. 18, A-8700 Leoben (Austria); Teichert, C., E-mail: Christian.Teichert@unileoben.ac.at [Institute of Physics, Montanuniversitaet Leoben, Franz Josef Str. 18, A-8700 Leoben (Austria); Oehme, M.; Werner, J.; Lyutovich, K.; Kasper, E. [Institut fuer Halbleitertechnik, Universitaet Stuttgart, Pfaffenwaldring 47, D-70569 Stuttgart (Germany)

    2009-10-15

    Ion assisted molecular beam epitaxy bears the potential to tune morphological and structural parameters of semiconductor heterolayers for opto- and nanoelectronic applications. The morphology evolution and the degree of relaxation are influenced by the ion beam parameters and the strain of the heteroepitaxial film. In this work, the morphology of silicon germanium (SiGe) layers due to Si{sup +}-ion beam treatment during growth is investigated by atomic force microscopy (AFM) as a function of ion energy and ion flux density. Ion energies range from 100 eV to 1000 eV. The AFM measurements are used to determine the roughness distribution across the wafers. A regular pattern of SiGe crystallites is found, where the damage due to low ion energy Si{sup +}-ion bombardment is medium and the degree of relaxation, determined by Raman spectroscopy, is below 25%.

  11. Si/Ge double-layered nanotube array as a lithium ion battery anode.

    Science.gov (United States)

    Song, Taeseup; Cheng, Huanyu; Choi, Heechae; Lee, Jin-Hyon; Han, Hyungkyu; Lee, Dong Hyun; Yoo, Dong Su; Kwon, Moon-Seok; Choi, Jae-Man; Doo, Seok Gwang; Chang, Hyuk; Xiao, Jianliang; Huang, Yonggang; Park, Won Il; Chung, Yong-Chae; Kim, Hansu; Rogers, John A; Paik, Ungyu

    2012-01-24

    Problems related to tremendous volume changes associated with cycling and the low electron conductivity and ion diffusivity of Si represent major obstacles to its use in high-capacity anodes for lithium ion batteries. We have developed a group IVA based nanotube heterostructure array, consisting of a high-capacity Si inner layer and a highly conductive Ge outer layer, to yield both favorable mechanics and kinetics in battery applications. This type of Si/Ge double-layered nanotube array electrode exhibits improved electrochemical performances over the analogous homogeneous Si system, including stable capacity retention (85% after 50 cycles) and doubled capacity at a 3C rate. These results stem from reduced maximum hoop strain in the nanotubes, supported by theoretical mechanics modeling, and lowered activation energy barrier for Li diffusion. This electrode technology creates opportunities in the development of group IVA nanotube heterostructures for next generation lithium ion batteries.

  12. Variations of δ 30Si and Ge/Si with weathering and biogenic input in tropical basaltic ash soils under monoculture

    Science.gov (United States)

    Opfergelt, S.; Cardinal, D.; André, L.; Delvigne, C.; Bremond, L.; Delvaux, B.

    2010-01-01

    In soils, silicon released by mineral weathering can be retrieved from soil solution through clay formation, Si adsorption onto secondary oxides and plant uptake, thereby impacting the Si-isotopic signature and Ge/Si ratio of dissolved Si (DSi) exported to rivers. Here we use these proxies to study the contribution of biogenic Si (BSi) in a soil-plant system involving basaltic ash soils differing in weathering degree under intensive banana cropping. δ 30Si and Ge/Si ratios were determined in bulk soils (banana phytoliths and a stable phytolith pool from previous forested vegetation. δ 30Si and Ge/Si values of clay fractions in poorly developed volcanic soils, isotopically heavier and Ge-depleted in surface horizons, support the occurrence of a DSi source from banana phytolith dissolution, available for Si sequestration in clay-sized secondary minerals (clay minerals formation and Si adsorption onto Fe-oxide). In the soil-plant system, δ 30Si and Ge/Si are thus highly relevant to trace weathering and input of DSi from phytoliths in secondary minerals, although not quantifying the net input of BSi to DSi.

  13. Tilting structures in inverse perovskites, M3TtO (M = Ca, Sr, Ba, Eu; Tt = Si, Ge, Sn, Pb).

    Science.gov (United States)

    Nuss, Jürgen; Mühle, Claus; Hayama, Kyouhei; Abdolazimi, Vahideh; Takagi, Hidenori

    2015-06-01

    Single-crystal X-ray diffraction experiments were performed for a series of inverse perovskites, M3TtO (M = Ca, Sr, Ba, Eu; Tt = tetrel element: Si, Ge, Sn, Pb) in the temperature range 500-50 K. For Tt = Sn, Pb, they crystallize as an 'ideal' perovskite-type structure (Pm3m, cP5); however, all of them show distinct anisotropies of the displacement ellipsoids of the M atoms at room temperature. This behavior vanishes on cooling for M = Ca, Sr, Eu, and the structures can be regarded as `ideal' cubic perovskites at 50 K. The anisotropies of the displacement ellipsoids are much more enhanced in the case of the Ba compounds. Finally, their structures undergo a phase transition at ∼ 150 K. They change from cubic to orthorhombic (Ibmm, oI20) upon cooling, with slightly tilted OBa6 octahedra, and bonding angles O-Ba-O ≃ 174° (100 K). For the larger Ba(2+) cations, the structural changes are in agreement with smaller tolerance factors (t) as defined by Goldschmidt. Similar structural behavior is observed for Ca3TtO. Smaller Tt(4-) anions (Si, Ge) introduce reduced tolerance factors. Both compounds Ca3SiO and Ca3GeO with cubic structures at 500 K, change into orthorhombic (Ibmm) at room temperature. Whereby, Ca3SiO is the only representative within the M3TtO family where three polymorphs can be found within the temperature range 500-50 K: Pm3m-Ibmm-Pbnm. They show tiny differences in the tilting of the OCa6 octahedra, expressed by O-Ca-O bond angles of 180° (500 K), ∼ 174° (295 K) and 170° (100 K). For larger M (Sr, Eu, Ba), together with smaller Tt (Si, Ge) atoms, pronounced tilting of the OM6 octahedra, and bonding angles of O-M-O ≃ 160° (295 K) are observed. They crystallize in the anti-GdFeO3 type of structure (Pbnm, oP20), and no phase transitions occur between 500 and 50 K. The observed phase transitions are all accompanied by multiple twinning, in terms of pseudo-merohedry or reticular pseudo-merohedry.

  14. Multiexciton complex from extrinsic centers in AlGaAs epilayers on Ge and Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sarti, F.; Muñoz Matutano, G.; Bauer, D.; Dotti, N.; Vinattieri, A.; Gurioli, M., E-mail: gurioli@lens.unifi.it [Dipartimento di Fisica e Astronomia, LENS and CNISM, Università di Firenze, Via Sansone 1, I-50019 Firenze (Italy); Bietti, S.; Sanguinetti, S. [Dipartimento di Scienza dei Materiali and L-NESS, Università di Milano Bicocca, Via Cozzi 53, I-20125 Milano (Italy); Isella, G. [Dipartimento di Fisica and L-NESS, Politecnico di Milano, Via Anzani 42, 22100 Como (Italy)

    2013-12-14

    The multiexciton properties of extrinsic centers from AlGaAs layers on Ge and Si substrates are addressed. The two photon cascade is found both in steady state and in time resolved experiments. Polarization analysis of the photoluminescence provides clearcut attribution to neutral biexciton complexes. Our findings demonstrate the prospect of exploiting extrinsic centers for generating entangled photon pairs on a Si based device.

  15. Dynamics of interstitial atoms and vacancies during the crystallization of amorphous Si and Ge films by flash lamp annealing

    Science.gov (United States)

    Matsuo, Naoto; Yoshioka, Naoki; Heya, Akira

    2017-08-01

    We examined the dynamics of interstitial atoms and vacancies in amorphous Si (a-Si) and a-Ge films crystallized by flash lamp annealing in consideration of the self-diffusion coefficients of Si and Ge. We found that the interstitial atoms play an important role in the liquid-phase crystallization (LPC) of a-Si films, whereas the vacancies are more important for the solid-phase crystallization (SPC) of a-Si films along with the LPC and SPC of a-Ge films. For Si, the crystal defect density of the film crystallized by LPC was higher than that of the film crystallized by SPC; the opposite result was achieved for Ge. This phenomenon is considered to be attributed to the existence of interstitial atoms introduced in Si. The thermodynamic calculated results related to the relationship between the point defect and SPC or LPC supported the crystallization mechanism.

  16. Longitudinl strain profile in GeSi/Si superlattice%GeSi/Si应变结构内应力纵向分布

    Institute of Scientific and Technical Information of China (English)

    肖剑飞; 封松林; 彭长四

    1997-01-01

    利用深能级瞬态谱(DLTS)研究分子束外延n-Ge0.2Si08/Si应变超晶格,观察到两个与位错有关的深中心,其中一个能级位置在EC=0.42eV,另一个随着偏压变化而发生明显的移动,深能级位置从EC=0.21eV变化到Ec=0.276eV,我们认为是内应力引起的.取该深能级的流体静压力系数γ=6.59meV/Kba,求出超晶格中的应力分布与计算值符合较好.在此基础上提出了一种通过测量深能级随应力移动效应来确定应变结构内应力纵向分布的新方法.

  17. Observation of short range ferromagnetic interactions and magnetocaloric effect in cobalt substituted Gd5Si2Ge2.

    Science.gov (United States)

    Uthaman, Bhagya; Manju, P; Thomas, Senoy; Jaiswal Nagar, Deepshikha; Suresh, K G; Varma, Manoj Raama

    2017-05-17

    We report on the observation of double transition - a first order and a second order transition in Gd5Si2-xCoxGe2 with x = 0, 0.1, 0.2 and 0.4 with the appearance of short-range ferromagnetic correlations. The first order phase transition is due to a combined magnetostructural transition from monoclinic paramagnetic phase to orthorhombic ferromagnetic phase on cooling while the second order transition arises from an orthorhombic paramagnetic to ferromagnetic phase on cooling. Structural studies show that the substituted compounds crystallize in a combination of Gd5Si2Ge2 and Gd5Si4 phases. Low-temperature X-ray diffraction measurements confirm the complete transformation from monoclinic to orthorhombic phase. DC magnetization measurements reveal an anomalous low field magnetic behaviour indicating a Griffiths-like phase. This unusual behaviour is attributed to the local disorder within the crystallographic structure indicating the presence of short-range magnetic correlations and ferromagnetic clustering, which is stabilized and enhanced by competing intra-layer and inter-layer magnetic interactions. The magnetostructural transition results in entropy changes (-ΔSM) of 9 J kg(-1) K(-1) at 260 K for x = 0.1, 8.5 J kg(-1) K(-1) at 245 K for x = 0.2 and 4.2 J kg(-1) K(-1) at 210 K for x = 0.4 for a field change of 50 kOe. Co substitution induces compelling crystallographic and magnetoresponsive effects in the Gd-Si-Ge system, which could be useful for potential and smart applications such as solid-state magnetic refrigeration and sensitive magnetic switching from paramagnetic to ferromagnetic state. Universal curve analysis has been carried out on the substituted samples to study the order of the magnetic transition.

  18. Low Temperature Deposition of High-k/Metal Gate Stacks on High-Sn Content (Si)GeSn-Alloys

    OpenAIRE

    Schulte-Braucks, C; Von Den Driesch, N; Glass, S; Tiedemann, AT; Breuer, U; Besmehn, A; Hartmann, JM; Ikonic, Z; Zhao, QT; Mantl, S; Buca, D.

    2016-01-01

    (Si)GeSn is an emerging group IV alloy system offering new exciting properties, with great potential for low power electronics due to the fundamental direct band gap and prospects as high mobility material. In this Article, we present a systematic study of HfO2/TaN high-k/metal gate stacks on (Si)GeSn ternary alloys and low temperature processes for large scale integration of Sn based alloys. Our investigations indicate that SiGeSn ternaries show enhanced thermal stability compared to GeSn bi...

  19. Surface structure of thin pseudomorphous GeSi layers

    Science.gov (United States)

    Nikiforov, A. I.; Timofeev, V. F.; Pchelyakov, O. P.

    2015-11-01

    Reflection high-energy electron diffraction (RHEED) was used to study the evolution of thin GexSi1-x film surface superstructures s in the course of molecular beam epitaxy. The (2 × N) superstructure of the epitaxial film surface at periodicity N from 14 to 8, the latter being characteristic of pure germanium at the Si(1 0 0) surface. The epitaxial film thickness that is required for the formation of the (2 × 8) superstructure depends on the deposition temperature and germanium content in the solid solution. The germanium segregation on the growing film surface is shown to be responsible for the observed superstructural changes.

  20. Defect Characterization in SiGe/SOI Epitaxial Semiconductors by Positron Annihilation

    Directory of Open Access Journals (Sweden)

    Ferragut R

    2010-01-01

    Full Text Available Abstract The potential of positron annihilation spectroscopy (PAS for defect characterization at the atomic scale in semiconductors has been demonstrated in thin multilayer structures of SiGe (50 nm grown on UTB (ultra-thin body SOI (silicon-on-insulator. A slow positron beam was used to probe the defect profile. The SiO2/Si interface in the UTB-SOI was well characterized, and a good estimation of its depth has been obtained. The chemical analysis indicates that the interface does not contain defects, but only strongly localized charged centers. In order to promote the relaxation, the samples have been submitted to a post-growth annealing treatment in vacuum. After this treatment, it was possible to observe the modifications of the defect structure of the relaxed film. Chemical analysis of the SiGe layers suggests a prevalent trapping site surrounded by germanium atoms, presumably Si vacancies associated with misfit dislocations and threading dislocations in the SiGe films.

  1. Properties of laser-crystallized polycrystalline SiGe thin films

    Energy Technology Data Exchange (ETDEWEB)

    Weizman, Moshe

    2008-06-06

    In this thesis, structural, electrical, and optical properties of laser-crystallized polycrystalline Si{sub 1-x}Ge{sub x} thin films with 0Si{sub 1-x}Ge{sub x} thin films with 0.3SiGe samples that are exposed to a single laser pulse exhibit a ripple structure that evolves into a hillock structure when the samples are irradiated with additional laser pulses. - It is maintained that the main mechanism behind the structure formation is an instability of the propagating solid-liquid interface during solidification. - The study of defects with electron spin resonance showed that laser-crystallized poly-Si{sub 1-x}Ge{sub x} thin films with 0Ge content. The defect density for solid-phase crystallized SiGe films was lower and amounted to N{sub s}=7 x 10{sup 17} cm{sup -3}. - Germanium-rich laser-crystallized poly-SiGe thin films exhibited mostly a broad atypical electric dipole spin resonance (EDSR) signal that was accompanied by a nearly temperature-independent electrical conductivity in the range 20-100 K. - Most likely, the origin of the grain boundary conductance is due to dangling-bond defects and not impurities. Metallic-like conductance occurs when the dangling-bond defect density is above a critical value of about N{sub C} {approx} 10{sup 18} cm{sup -3}. - Laser crystallized poly-Si{sub 1-x}Ge{sub x} thin films with x{>=}0.5 exhibit optical absorption behavior that is characteristic for disordered SiGe, implying that the absorption occurs primarily at the grain boundaries. A sub-band-gap absorption peak was found for

  2. Preparation of Si sub 1 sub - sub x sub - sub y Ge sub x C sub y semiconductor films on Si by ion implantation and solid phase epitaxy

    CERN Document Server

    Liu Xue Qin; Zhen Cong Mian; Zhang Jing; Yang Yi; Guo Yong

    2002-01-01

    Si sub 1 sub - sub x sub - sub y Ge sub x C sub y ternary alloy semiconductor films were prepared on Si(100) substrates by C ion implanting SiGe films and subsequent solid phase epitaxy (SPE). Two-step annealing technique was employed in the SPE processing. The properties of the alloy films were determined using Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscopy (FTIR) and High-resolution x-ray diffraction (HRXRD) measurements. It is shown that C atoms are located at substitutional sites and the incorporation of C relieves the compressive strain in the SiGe layer

  3. Initial stage growth of GexSi1-x layers and Ge quantum dot formation on GexSi1-x surface by MBE.

    Science.gov (United States)

    Nikiforov, Aleksandr I; Timofeev, Vyacheslav A; Teys, Serge A; Gutakovsky, Anton K; Pchelyakov, Oleg P

    2012-10-09

    Critical thicknesses of two-dimensional to three-dimensional growth in GexSi1-x layers were measured as a function of composition for different growth temperatures. In addition to the (2 × 1) superstructure for a Ge film grown on Si(100), the GexSi1-x layers are characterized by the formation of (2 × n) reconstruction. We measured n for all layers of Ge/GexSi1-x/Ge heterosystem using our software with respect to the video recording of reflection high-energy electron diffraction (RHEED) pattern during growth. The n reaches a minimum value of about 8 for clear Ge layer, whereas for GexSi1-x films, n is increased from 8 to 14. The presence of a thin strained film of the GexSi1-x caused not only the changes in critical thicknesses of the transitions, but also affected the properties of the germanium nanocluster array for the top Ge layer. Based on the RHEED data, the hut-like island form, which has not been previously observed by us between the hut and dome islands, has been detected. Data on the growth of Ge/GexSi1-x/Ge heterostructures with the uniform array of islands in the second layer of the Ge film have been received.

  4. Chemically selective formation of Si-O-Al on SiGe(110) and (001) for ALD nucleation using H2O2(g)

    Science.gov (United States)

    Park, Sang Wook; Kim, Hyonwoong; Chagarov, Evgueni; Siddiqui, Shariq; Sahu, Bhagawan; Yoshida, Naomi; Kachian, Jessica; Feenstra, Randall; Kummel, Andrew C.

    2016-10-01

    Passivation and functionalization via atomic hydrogen, hydrogen peroxide (H2O2(g)), and trimethylaluminum (TMA) on clean silicon-germanium (Si0.5Ge0.5(110) and Si0.47Ge0.53(001)) surfaces were studied and compared at the atomic level using ultra-high vacuum (UHV) scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and X-ray photoelectron spectroscopy (XPS) to understand the topological, electronic, and chemical structures of the surfaces. STM and XPS indicate that a sputter-cleaned SiGe(110) surface is terminated with adatoms, while a SiGe(001) surface is terminated with germanium dimers. STS demonstrates that the Fermi level on a clean SiGe(110) surface is pinned near mid-gap due to surface dangling bonds, while the Fermi level on a clean SiGe(001) surface is consistent with unpinning. A saturation dose of H2O2(g) at 25 °C chemisorbs to SiGe surfaces, leaving the Fermi level at the surface consistent with unpinning, and the surface is functionalized mainly with Si-OH, Ge-OH, and Si-O-Ge bonds on both SiGe(110) and (001). After a subsequent TMA dose at 25 °C, XPS and STM verify that a thermally stable and well-ordered monolayer of Al2O3 is formed on SiGe(110) and (001) surfaces, resulting in the formation of Al-O-Si bonds. The H2O2(g) functionalization provides three times more oxygen sites on the surface and three times as great a TMA nucleation density than does H2O(g) at both 25 °C and 120 °C. STS demonstrates that H2O2(g)- and TMA-dosed SiGe surfaces show a Fermi level consistent with unpinning and a local density of states (DOS) without any states between the conduction and valence band edge, indicating an ideal template for further atomic layer deposition (ALD) nucleation of high-k materials on SiGe(110) and (001) surfaces.

  5. Formation of Si or Ge nanodots in Si3N4 with in-situ donor modulation doping of adjacent barrier material

    Directory of Open Access Journals (Sweden)

    D. König

    2013-01-01

    Full Text Available Conventional doping of small nanodots does not provide majority carriers due to self-purification effects and much increased ionisation energies of dopants presenting point defects. Adjacent barrier layers to Si-rich Si3N4 can be doped by excess Si in-situ with the segregation anneal for Si nanodot formation. Donor doping of AlxGa1−xN (0 ⩽ x ⩽ 1 with Si is an established process. Material properties and process compatibility of AlxGa1−xN render it suitable as barrier for Si nanodot superlattices. Ab-initio calculations showed that Ge also works as a donor in AlN, extending the material range to Ge and SiGe nanodots in Si3N4.

  6. Heteroepitaxy of Ge on Si(001) with pits and windows transferred from free-standing porous alumina mask

    Science.gov (United States)

    Huangfu, Yourui; Zhan, Wenbo; Hong, Xia; Fang, Xu; Ding, Guqiao; Ye, Hui

    2013-05-01

    This paper reports the use of ultrathin free-standing porous alumina membrane (PAM) in pattern transferring for selective epitaxial growth (SEG) of Ge dots and films on Si. PAM, as a large-scale, controllable and lithography-free mask, can transfer nanopatterns onto Si without introducing any contaminants. High-density Ge dots are achievable with Ge adatoms confined in Si pits transferred from PAM. High-quality Ge films can also be grown on Si substrates through SiO2 nano-windows. In this work, 80 and 60 nm pore sizes of PAM were transferred to 70, 50 and 20 nm windows for comparison. For the former two sizes, over-etching of Si beneath every SiO2 window forms epi-seeds to improve intermixing of Ge-Si. No threading dislocations can be observed emanating from the epi-seeds due to the decreased lattice mismatch. An innovative shadow-etching technique utilizing the aspect ratio of PAM further decreased the lateral dimension of patterns from 60 to 20 nm. Cross-sectional transmission electron microscopy images show that the selective epitaxial Ge films grown from a 20 nm-width interface are defect free, which is attributed to the exponential decay of strain energy as well as Ge-Si intermixing.

  7. De-embedding and Modelling of pnp SiGe HBTs

    DEFF Research Database (Denmark)

    Hadziabdic, Dzenan; Jiang, Chenhui; Johansen, Tom Keinicke

    2007-01-01

    In this work we present a direct parameter extraction procedure for SiGe pnp heterojunction bipolar transistor (HBT) large-signal and small-signal models. Test structure parasitics are removed from the measured small-signal parameters using an open-short de-embedding technique, improved to account...

  8. Structural and thermoelectric properties of SiGe/Al multilayer systems during metal induced crystallization

    Science.gov (United States)

    Lindorf, M.; Rohrmann, H.; Span, G.; Raoux, S.; Jordan-Sweet, J.; Albrecht, M.

    2016-11-01

    While the process of metal induced crystallization (MIC) is widely used in the fabrication of thin film electronic devices, its application to the field of thermoelectrics is fairly new. Especially, its implementation in the field of the classic thermoelectric material SiGe could lead to a low cost approach by combining the benefits of low thermal budget, self-doping, and thin film and sputter deposition compatibility. In this work, samples consisting of SiGe/Al multilayers deposited on aluminum oxide based substrates have been prepared. Special emphasis was put on the ratio of Al to SiGe and the resulting changes in transport properties during annealing. On one hand, a certain amount of Al is needed to ensure a complete MIC process for the SiGe, but on the other hand, an excess of Al results in a metallic system with low thermoelectric efficiency. In-situ characterization during annealing of the samples was carried out via x-ray diffraction, electrical resistivity, and Seebeck measurements.

  9. First Principles Study of Si/Ge Core-Shell nanowires under external uniaxial strain

    CERN Document Server

    Peng, Xihong; Logan, Paul

    2010-01-01

    Density-functional theory based first principles calculations are performed to study the effects of external uniaxial strain on the electronic states of Si/Ge core-shell nanowires along the [110] direction with the diameter of the wire up to 5 nm. As shown in the calculations, the [110] Si/Ge core-shell nanowires without external strain possess a direct band gap, in contrast to the nature of an indirect band gap in bulk Si and Ge. The band structure of the core-shell nanowires can be significantly modulated by an external strain. With a sufficient amount of tensile uniaxial strain, the band gap of the Si/Ge core-shell nanowires experiences a transition from direct to indirect. In addition, our studies showed that the effective masses of charge carriers can be also tuned by the external uniaxial strain. The effective mass of the hole increases dramatically with a tensile strain, while strain shows a minimal effect on tuning the effective mass of the electron. Finally, the relationship between the strain effect...

  10. New low-stress PECVD poly-SiGe layers for MEMS

    NARCIS (Netherlands)

    Rusu, C.R.; Sedky, Sherif; Parmentier, Brigette; Verbist, Agnes; Richard, Olivier; Brijs, Bert; Geenen, Luc; Witvrouw, Ann; Lärmer, Franz; Fischer, Frank; Kronmüller, Silvia; Leca, V.; Otter, A.M.

    2003-01-01

    Thick poly-SiGe layers, deposited by plasma-enhanced chemical vapor deposition (PECVD), are very promising structural layers for use in microaccelerometers, microgyroscopes or for thin-film encapsulation, especially for applications where the thermal budget is limited. In this work it is shown for

  11. Improvement of magnetocaloric properties of Gd-Ge-Si alloys by alloying with iron

    Directory of Open Access Journals (Sweden)

    Erenc-Sędziak T.

    2013-01-01

    Full Text Available The influence of annealing of Gd5Ge2Si2Fex alloys at 1200°C and of alloying with various amount of iron on structure as well as thermal and magnetocaloric properties is investigated. It was found that annealing for 1 t