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Sample records for wide-gap semiconductor znte

  1. Searching Room Temperature Ferromagnetism in Wide Gap Semiconductors Fe-doped Strontium Titanate and Zinc Oxide

    CERN Document Server

    Pereira, LMC; Wahl, U

    Scientific findings in the very beginning of the millennium are taking us a step further in the new paradigm of technology: spintronics. Upgrading charge-based electronics with the additional degree of freedom of the carriers spin-state, spintronics opens a path to the birth of a new generation of devices with the potential advantages of non-volatility and higher processing speed, integration densities and power efficiency. A decisive step towards this new age lies on the attribution of magnetic properties to semiconductors, the building block of today's electronics, that is, the realization of ferromagnetic semiconductors (FS) with critical temperatures above room temperature. Unfruitful search for intrinsic RT FS lead to the concept of Dilute(d) Magnetic Semiconductors (DMS): ordinary semiconductor materials where 3 d transition metals randomly substitute a few percent of the matrix cations and, by some long-range mechanism, order ferromagnetically. The times are of intense research activity and the last fe...

  2. The Theory of ESR Hyperfine-Structure Narrowing as Applied to Wide-Gap Semimagnetic Semiconductors

    Science.gov (United States)

    Aliev; Tagirov; Tagiev

    1996-11-01

    The theory of ESR hyperfine-structure exchange narrowing is developed. The kinetic equations describing the nonequilibrium magnetization dynamics of hyperfine components of ESR spectra are derived by using the nonequilibrium statistical-operator method. Numerical solution of these general equations is applied to the simulation of the experimental spectra of (Cd, Mn)Te crystals with a Mn2+ ion content of between 0.05 and 0.5%. The hyperfine-splitting constant, homogeneous ESR linewidth, and mean-square value of the exchange fluctuation frequency are obtained from the fitting of the spectra for different concentrations of manganese ions. The concentration dependence of the latter quantity is discussed in relation to the spatial dependence of magnetic-ion exchange interaction and the gap value in the band structure of semimagnetic semiconductors.

  3. L-asparagine crystals with wide gap semiconductor features: Optical absorption measurements and density functional theory computations

    Energy Technology Data Exchange (ETDEWEB)

    Zanatta, G.; Gottfried, C. [Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, 90035-003 Porto Alegre-RS (Brazil); Silva, A. M. [Universidade Estadual do Piauí, 64260-000 Piripiri-Pi (Brazil); Caetano, E. W. S., E-mail: ewcaetano@gmail.com [Instituto de Educação, Ciência e Tecnologia do Ceará, 60040-531 Fortaleza-CE (Brazil); Sales, F. A. M.; Freire, V. N. [Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, 60455-760 Fortaleza-CE (Brazil)

    2014-03-28

    Results of optical absorption measurements are presented together with calculated structural, electronic, and optical properties for the anhydrous monoclinic L-asparagine crystal. Density functional theory (DFT) within the generalized gradient approximation (GGA) including dispersion effects (TS, Grimme) was employed to perform the calculations. The optical absorption measurements revealed that the anhydrous monoclinic L-asparagine crystal is a wide band gap material with 4.95 eV main gap energy. DFT-GGA+TS simulations, on the other hand, produced structural parameters in very good agreement with X-ray data. The lattice parameter differences Δa, Δb, Δc between theory and experiment were as small as 0.020, 0.051, and 0.022 Å, respectively. The calculated band gap energy is smaller than the experimental data by about 15%, with a 4.23 eV indirect band gap corresponding to Z → Γ and Z → β transitions. Three other indirect band gaps of 4.30 eV, 4.32 eV, and 4.36 eV are assigned to α3 → Γ, α1 → Γ, and α2 → Γ transitions, respectively. Δ-sol computations, on the other hand, predict a main band gap of 5.00 eV, just 50 meV above the experimental value. Electronic wavefunctions mainly originating from O 2p–carboxyl, C 2p–side chain, and C 2p–carboxyl orbitals contribute most significantly to the highest valence and lowest conduction energy bands, respectively. By varying the lattice parameters from their converged equilibrium values, we show that the unit cell is less stiff along the b direction than for the a and c directions. Effective mass calculations suggest that hole transport behavior is more anisotropic than electron transport, but the mass values allow for some charge mobility except along a direction perpendicular to the molecular layers of L-asparagine which form the crystal, so anhydrous monoclinic L-asparagine crystals could behave as wide gap semiconductors. Finally, the calculations point to a high degree of optical

  4. L-Asparagine crystals with wide gap semiconductor features: optical absorption measurements and density functional theory computations.

    Science.gov (United States)

    Zanatta, G; Gottfried, C; Silva, A M; Caetano, E W S; Sales, F A M; Freire, V N

    2014-03-28

    Results of optical absorption measurements are presented together with calculated structural, electronic, and optical properties for the anhydrous monoclinic L-asparagine crystal. Density functional theory (DFT) within the generalized gradient approximation (GGA) including dispersion effects (TS, Grimme) was employed to perform the calculations. The optical absorption measurements revealed that the anhydrous monoclinic L-asparagine crystal is a wide band gap material with 4.95 eV main gap energy. DFT-GGA+TS simulations, on the other hand, produced structural parameters in very good agreement with X-ray data. The lattice parameter differences Δa, Δb, Δc between theory and experiment were as small as 0.020, 0.051, and 0.022 Å, respectively. The calculated band gap energy is smaller than the experimental data by about 15%, with a 4.23 eV indirect band gap corresponding to Z → Γ and Z → β transitions. Three other indirect band gaps of 4.30 eV, 4.32 eV, and 4.36 eV are assigned to α3 → Γ, α1 → Γ, and α2 → Γ transitions, respectively. Δ-sol computations, on the other hand, predict a main band gap of 5.00 eV, just 50 meV above the experimental value. Electronic wavefunctions mainly originating from O 2p-carboxyl, C 2p-side chain, and C 2p-carboxyl orbitals contribute most significantly to the highest valence and lowest conduction energy bands, respectively. By varying the lattice parameters from their converged equilibrium values, we show that the unit cell is less stiff along the b direction than for the a and c directions. Effective mass calculations suggest that hole transport behavior is more anisotropic than electron transport, but the mass values allow for some charge mobility except along a direction perpendicular to the molecular layers of L-asparagine which form the crystal, so anhydrous monoclinic L-asparagine crystals could behave as wide gap semiconductors. Finally, the calculations point to a high degree of optical

  5. Designing defect-based qubit candidates in wide-gap binary semiconductors for solid-state quantum technologies

    Science.gov (United States)

    Seo, Hosung; Ma, He; Govoni, Marco; Galli, Giulia

    2017-12-01

    The development of novel quantum bits is key to extending the scope of solid-state quantum-information science and technology. Using first-principles calculations, we propose that large metal ion-vacancy pairs are promising qubit candidates in two binary crystals: 4 H -SiC and w -AlN. In particular, we found that the formation of neutral Hf- and Zr-vacancy pairs is energetically favorable in both solids; these defects have spin-triplet ground states, with electronic structures similar to those of the diamond nitrogen-vacancy center and the SiC divacancy. Interestingly, they exhibit different spin-strain coupling characteristics, and the nature of heavy metal ions may allow for easy defect implantation in desired lattice locations and ensure stability against defect diffusion. To support future experimental identification of the proposed defects, we report predictions of their optical zero-phonon line, zero-field splitting, and hyperfine parameters. The defect design concept identified here may be generalized to other binary semiconductors to facilitate the exploration of new solid-state qubits.

  6. Lattice dynamics of local defects in wide-gap semiconductors; Schwingungsverhalten lokaler Defekte in Breitband-Halbleitern

    Energy Technology Data Exchange (ETDEWEB)

    Kaczmarczyk, G.

    2006-07-01

    The group III-nitrides and zinc oxide are in the focus of material research because of their high application potential. The presentation of the first UV laser diode as well as blue light emitting diodes were the preliminary highlights. Although of all technological progress many physical questions are still open. In this work some of these questions are examined experimentally with Raman-scattering and theoretically with valence-force calculations. Many physical properties such as strain and doping concentration affect the lattice dynamics. As a start the phonons of the center of the Brillouin-zone in GaN, AlN, InN and ZnO are studied with first-order Raman-scattering. These results are the basis for advanced investigations. The acoustical and optical modes at the zone boundary and their combinations and overtones are determinated from the second-order Raman-scattering. Using the valence-force calculations the experimental frequencies are assigned to particular phonon branches or points of the Brillouin zone. The second part of this work treats systematically the physics of local vibrational modes. They occur due to intrinsic defects or impurities in the semiconductors. They are investigated with respect to the vibrational properties of the unperturbed crystals. In order to assign new experimentally found structures, calculations of local vibrational modes in GaN:Mg, GaN:As and ZnO:N systems were carried out. Furthermore, the calculations in Si- and C-doped hexagonal GaN suggest the frequency range for local vibrational modes. In the last section the influence of external parameters such as temperature or strain on the phonon frequency is analyzed. It is shown, that the influence on the temperature dependence of host phonons and local vibrational modes are dominated through different effects. In case of the host phonons it is mainly due to the volume effect whereas the local modes are highly affected by the anharmonic decay. Moreover, the calculations verified

  7. ZnTe Semiconductor-Polymer Gel Composited Electrolyte for Conversion of Solar Energy

    Directory of Open Access Journals (Sweden)

    Wonchai Promnopas

    2014-01-01

    Full Text Available Nanostructured cubic p-type ZnTe for dye sensitized solar cells (DSSCs was synthesized from 1 : 1 molar ratio of Zn : Te by 600 W and 900 W microwave plasma for 30 min. In this research, their green emissions were detected at the same wavelengths of 563 nm, the energy gap (Eg at 2.24 eV, and three Raman shifts at 205, 410, and 620 cm−1. The nanocomposited electrolyte of quasisolid state ZnO-DSSCs was in correlation with the increase in the JSC, VOC, fill factor (ff, and efficiency (η by increasing the wt% of ZnTe-GPE (gel polymer electrolyte to an optimum value and decreased afterwards. The optimal ZnO-DSSC performance was achieved for 0.20 wt% ZnTe-GPE with the highest photoelectronic energy conversion efficiency at 174.7% with respect to that of the GPE without doping of p-type ZnTe.

  8. Wide-Gap Chalcopyrites

    CERN Document Server

    Siebentritt, Susanne

    2006-01-01

    Chalcopyrites, in particular those with a wide band gap, are fascinating materials in terms of their technological potential in the next generation of thin-film solar cells and in terms of their basic material properties. They exhibit uniquely low defect formation energies, leading to unusual doping and phase behavior and to extremely benign grain boundaries. This book collects articles on a number of those basic material properties of wide-gap chalcopyrites, comparing them to their low-gap cousins. They explore the doping of the materials, the electronic structure and the transport through interfaces and grain boundaries, the formation of the electric field in a solar cell, the mechanisms and suppression of recombination, the role of inhomogeneities, and the technological role of wide-gap chalcopyrites.

  9. Contribution to the study of electronic structure of crystalline semiconductors (Si, Ge, GaAs, Gap, ZnTe, ZnSe

    Directory of Open Access Journals (Sweden)

    Bouhafs B.

    2012-06-01

    Full Text Available The band structure of semiconductors was described by several theorists since the Fifties. The main objective of the present paper is to do a comparative study between various families of semi-conductors IV (Si,Ge, III-V (GaAs, GaP and II-VI (ZnSe, ZnTe with both methods; tight Binding1 method and pseudo potential method2. This work enables us to understand as well as the mechanism of conduction process in these semiconductors and powers and limits of the above methods. The obtained results allow to conclude that both methods are in a good agreement to describe the morphology of band structures of the cited semiconductors. This encourages us to study in the future the electronic behaviour through the structure of bands for more complex systems such as the heterostructures.

  10. Reduced electrical performance of Zn enriched ZnTe nanoinclusion semiconductors thin films for buffer layer in solar cells

    Science.gov (United States)

    Mahmood, Waqar; Thomas, Andrew; Haq, Anwar ul; Shah, Nazar Abbas; Farooq Nasir, Muhammad

    2017-06-01

    Closed space sublimation (CSS) technique was employed to deposit thin films of zinc telluride (ZnTe) on a glass substrate under high vacuum. Two sets of ZnTe thin films and Zn enriched ZnTe thin films were prepared for comparative study. The enrichment for Zn onto the as-deposited ZnTe thin films was done by the novel manner of layer by layer deposition with subsequent annealing. X-ray diffraction (XRD) studies revealed before and after the enrichment of Zn the preferred orientation is [1 1 1] having cubic phase. The lattice constant was found to be increased and the crystallite size decreased 28 nm to 24 nm after the enrichment of Zn. A morphological study was carried out through a scanning electron microscope (SEM). For Zn enriched samples the average grain size is smaller as compared to ZnTe thin films. The local compositions of Zn and Te were confirmed by energy dispersive x-rays (EDX) from 51 atomic % of as-deposited ZnTe thin films to 68 atomic % in Zn enriched ZnTe thin films. The Zn enriched samples have a slight decrease in optical transmission in UV-VIS-NIR range as compared to the as-deposited ZnTe thin films. Due to the deposition of Zn there is a very small change in optical band gap energy. A four-probe technique was used to study electrical properties of as-deposited and Zn-enriched ZnTe thin films. These results shows that the as-deposited samples had the resistivity of 106 Ω · cm. For Zn enrichment samples resistivity increases from 106 Ω · cm to 108 Ω · cm, which shows that Zn-enriched samples are not suitable for back contact of II-VI solar cells. X-rays photoelectron spectroscopy (XPS) was used to confirm the elemental compositions and its bonding strength before and after the enrichment of Zn.

  11. X-ray diffraction study of epitaxial heterostructures of II-VI CdTe and ZnTe semiconductors; Etude par diffraction de rayons X d`heterostructures epitaxiees a base des semi-conducteurs II-VI CdTe et ZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Bouchet-Boudet, N.

    1996-10-07

    This work deals with the structural study of II-VI semiconductor (CdTe and ZnTe) heterostructures by X-ray diffraction and reflectivity. These heterostructures have a high lattice parameter misfit and are grown by Molecular Beam Epitaxy. Two main subjects are developed: the characterization of ZnTe wires, grown by step propagation on a CdTe (001) vicinal surface, and the study of the vertical correlations in Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattices and superlattices made of ZnTe fractional layers spaced by CdTe. The growth of organised system is up to date; its aim is to realize quantum boxes (or wires) superlattices which are laterally and vertically ordered. The deformation along the growth axis induced by a ZnTe fractional layer inserted in a CdTe matrix is modelled, in the kinematical approximation, to reproduce the reflectivity measured around the substrate (004) Bragg peak. The lateral periodicity of the wires, deposited on a vicinal surface is a new and difficult subject. Some results are obtained on a vertical superlattice grown on a 1 deg. mis-cut surface. The in-plane and out-of-plane correlation lengths of a Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattice are deduced from the diffused scattered intensity measured at grazing incidence. The calculations are made within the `distorted Wave Born Approximation`. The vertical correlation in ZnTe boxes (or wines) superlattices can be measured around Bragg peaks. It is twice bigger in a superlattice grown on a 2 deg. mis-cut substrate than a nominal one. (author). 74 refs.

  12. Use of separate ZnTe interface layers to form OHMIC contacts to p-CdTe films

    Science.gov (United States)

    Gessert, Timothy A.

    1999-01-01

    A method of improving electrical contact to a thin film of a p-type tellurium-containing II-VI semiconductor comprising: depositing a first undoped layer of ZnTe on a thin film of p-type tellurium containing II-VI semiconductor with material properties selected to limit the formation of potential barriers at the interface between the p-CdTe and the undoped layer, to a thickness sufficient to control diffusion of the metallic-doped ZnTe into the p-type tellurim-containing II-VI semiconductor, but thin enough to minimize affects of series resistance; depositing a second heavy doped p-type ZnTe layer to the first layer using an appropriate dopant; and depositing an appropriate metal onto the outer-most surface of the doped ZnTe layer for connecting an external electrical conductor to an ohmic contact.

  13. van der Waals epitaxial ZnTe thin film on single-crystalline graphene

    Science.gov (United States)

    Sun, Xin; Chen, Zhizhong; Wang, Yiping; Lu, Zonghuan; Shi, Jian; Washington, Morris; Lu, Toh-Ming

    2018-01-01

    Graphene template has long been promoted as a promising host to support van der Waals flexible electronics. However, van der Waals epitaxial growth of conventional semiconductors in planar thin film form on transferred graphene sheets is challenging because the nucleation rate of film species on graphene is significantly low due to the passive surface of graphene. In this work, we demonstrate the epitaxy of zinc-blende ZnTe thin film on single-crystalline graphene supported by an amorphous glass substrate. Given the amorphous nature and no obvious remote epitaxy effect of the glass substrate, this study clearly proves the van der Waals epitaxy of a 3D semiconductor thin film on graphene. X-ray pole figure analysis reveals the existence of two ZnTe epitaxial orientational domains on graphene, a strong X-ray intensity observed from the ZnTe [ 1 ¯ 1 ¯ 2] ǁ graphene [10] orientation domain, and a weaker intensity from the ZnTe [ 1 ¯ 1 ¯ 2] ǁ graphene [11] orientation domain. Furthermore, this study systematically investigates the optoelectronic properties of this epitaxial ZnTe film on graphene using temperature-dependent Raman spectroscopy, steady-state and time-resolved photoluminescence spectroscopy, and fabrication and characterization of a ZnTe-graphene photodetector. The research suggests an effective approach towards graphene-templated flexible electronics.

  14. ZnTe thin films grown by electrodeposition technique on Fluorine Tin Oxide substrates

    Energy Technology Data Exchange (ETDEWEB)

    Skhouni, O. [Laboratoire LOAOS, Département de Physique, Université Hassan II, Faculté des Sciences et Techniques, Bd Yasmina, BP 145 Mohammedia (Morocco); El Manouni, A. [Departament de Física Aplicada-ETSED, Universitat Politècnica de València, Camí de Vera s/n, 46022 Valencia (Spain); Laboratoire LOAOS, Département de Physique, Université Hassan II, Faculté des Sciences et Techniques, Bd Yasmina, BP 145 Mohammedia (Morocco); Mollar, M. [Departament de Física Aplicada-ETSED, Universitat Politècnica de València, Camí de Vera s/n, 46022 Valencia (Spain); Schrebler, R. [Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Av. Universidad 330, Curauma Valparaíso (Chile); Marí, B., E-mail: bmari@fis.upv.es [Departament de Física Aplicada-ETSED, Universitat Politècnica de València, Camí de Vera s/n, 46022 Valencia (Spain)

    2014-08-01

    Zinc telluride (ZnTe) thin films are prepared potentiostatically from an aqueous solution bath containing ZnCl{sub 2}, TeCl{sub 4} and LiCl on Fluorine Tin Oxide coated glass substrate to investigate its suitability as a material for solar cell technology. The appropriate potential region where formation of stoichiometric ZnTe semiconductor occurs is found to be close to − 0.85 V versus Ag/AgCl. X-ray diffraction results have indicated that all electrodeposited films have cubic structure. Quantitative analysis of energy dispersive X-ray analysis results has shown that the composition ratio (Zn:Te) of films is around (1:0.99). A direct energy gap of 2.19 eV is determined by NIR–Vis–UV spectroscopy. The effect of annealing on the crystallinity and optical properties has been reported. Impedance measurements have revealed that all grown films present a p-type electrical conductivity with acceptor density N{sub A} = 2.16 × 10{sup 19} cm{sup −3}. Furthermore, the impedance results are adjusted to an equivalent circuit having two capacitors in series (Helmholtz, C{sub H} and space charge, C{sub SC}) and two resistances R{sub CT} and R{sub SC}, which are associated with charge transfer processes. - Highlights: • ZnTe thin films were electrochemically synthetized. • We discuss the electrochemical reactions involved in ZnTe thin film formation. • ZnTe films are p-type semiconductor with acceptor concentration about 2 × 10{sup 19} cm{sup −3}. • EIS data are modeled with a two capacitor–two resistance equivalent circuit. • Faster charge transfer process occurs at the interface ZnTe/electrolitic solution.

  15. Photoresponse properties of ZnTe nanowire photodetectors

    Energy Technology Data Exchange (ETDEWEB)

    Shaygan, Mehrdad; Kheirabi, Nazli; Davami, Keivan; Lee, Jeong-Soo [Division of IT Convergence Engineering, Pohang University of Science and Technology, Pohang (Korea, Republic of); Cuniberti, Gianaurelio [Division of IT Convergence Engineering, Pohang University of Science and Technology, Pohang (Korea, Republic of); Institute for Materials Science and Max Bergmann Center of Biomaterials, Dresden University of Technology, Dresden (Germany); Meyyappan, Meyya [Division of IT Convergence Engineering, Pohang University of Science and Technology, Pohang (Korea, Republic of); NASA Ames Research Center, Moffett Field, CA 94035 (United States)

    2013-07-01

    Photoconductivity in semiconductors is the electrical conductivity enhancement due to the electron hole pair generation induced by radiation exposure. This phenomenon is the main mechanism of photodetection in sensors. There has been increasing interest for nanosensors of all kinds which can be light weight and less expensive and can be easily incorporated into MEMS/NEMS devices. Nanowires as one dimensional high aspect ratio nanostructures have several advantages over their bulk and thin film counterparts when applied as photodetectors. Zinc telluride, an important II-IV semiconductor with a direct band gap of 2.26 eV, has been considered as a prospective material for photosensing application. In this work, ZnTe nanowires have been synthesized by Vapor-Liquid-Solid method with optimized growth parameters. They have been incorporated in the well known single nanowire field effect transistor (SNFET) device structure to be electrically characterized in dark and under illumination. The wavelength dependent response of our ZnTe NW based photodetector has been investigated under near IR to near UV illumination.

  16. Dispersion of the second-order nonlinear susceptibility in ZnTe, ZnSe, and ZnS

    DEFF Research Database (Denmark)

    Wagner, Hans Peter; Kühnelt, M.; Langbein, Wolfgang Werner

    1998-01-01

    We have measured the absolute values of the second-harmonic generation (SHG) coefficient \\d\\ for the zinc-blende II-VI semiconductors ZnTe, ZnSe, and ZnS at room temperature. The investigated spectral region of the fundamental radiation lambda(F) ranges from 520 to 1321 nm using various pulsed...

  17. Intense white luminescence in ZnTe embedded porous silicon

    Science.gov (United States)

    de Melo, O.; de Melo, C.; Santana, G.; Santoyo, J.; Zelaya-Angel, O.; Mendoza-Álvarez, J. G.; Torres-Costa, V.

    2012-06-01

    Porous silicon layers were embedded with ZnTe using the isothermal close space sublimation technique. The presence of ZnTe was demonstrated using cross-sectional energy dispersive spectroscopy maps. ZnTe embedded samples present intense room temperature photoluminescence along the whole visible range. We ascribe this PL to ZnTe nanocrystals of different sizes grown on the internal pore surface. Such crystals, with different orientations and sizes, were observed in transmission electron microscopy images, while transmission electron diffraction images of the same regions reveal ZnTe characteristic patterns.

  18. Numerical study of the influence of ZnTe thickness on CdS/ZnTe solar cell performance

    Science.gov (United States)

    Skhouni, Othmane; El Manouni, Ahmed; Mari, Bernabe; Ullah, Hanif

    2016-05-01

    At present most of II-VI semiconductor based solar cells use the CdTe material as an absorber film. The simulation of its performance is realized by means of various numerical modelling programs. We have modelled a solar cell based on zinc telluride (ZnTe) thin film as absorber in substitution to the CdTe material, which contains the cadmium element known by its toxicity. The performance of such photovoltaic device has been numerically simulated and the thickness of the absorber layer has been optimized to give the optimal conversion efficiency. A photovoltaic device consisting of a ZnTe layer as absorber, CdS as the buffer layer and ZnO as a window layer was modelled through Solar Cell Capacitance Simulator Software. Dark and illuminated I-V characteristics and the results for different output parameters of ZnO/CdS/ZnTe solar cell were analyzed. The effect of ZnTe absorber thickness on different main working parameters such as: open-circuit voltage Voc, short-circuit current density Jsc, fill factor FF, photovoltaic conversion efficiency η was intensely studied in order to optimize ZnTe film thickness. This study reveals that increasing the thickness of ZnTe absorber layer results in higher efficiency until a maximum value and then decreases slightly. This maximum was found to be 10% at ZnTe optimum thickness close to 2 µm. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  19. Some spectral response characteristics of ZnTe thin films

    Indian Academy of Sciences (India)

    Unknown

    used in optoelectronic detection of THz radiation (Winnewis- ser et al 1997). Photoluminescence study on ZnTe was also carried out in recent years (Nishio et al 1999). The ZnTe thin films grown at room temperature and high temperature substrates are found to be polycrystalline in nature (Kalita et al 1999). By investigating ...

  20. Photoconductivity of ZnTe thin films at elevated temperatures

    Indian Academy of Sciences (India)

    Unknown

    made to assess the predominance of the Poole–Frenkel con- duction mechanism in the dark and photoconductivities of. ZnTe thin films at room temperature and higher ambient temperatures. 2. Experimental. ZnTe thin films of different thicknesses were deposited on properly cleaned glass substrates with the help of a Hind.

  1. Very High Quality Crystals of Wide-Gap II-VI Semiconductors: What for?

    Science.gov (United States)

    2001-01-01

    The second modification was the use of a Cd reservoir outside the crucible made of pyrolytic boron nitride , in which the crystal was growing. Both the...of very high quality. In particular, the density of dislocations measured as etch pit density ( EPD ) was of 2000 cmŖ. In the crystals grown from the...the reciprocal space mapping, by the etch pit density ( EPD ) measurements (to determine the density of dislocations) and by the measurement of the width

  2. Time-resolved ultrafast spectroscopy of wide-gap II-VI semiconductor quantum wells

    CERN Document Server

    Brown, G

    2001-01-01

    proposal is supported through the development of a phenomenological model describing the dynamic evolution of exciton spin populations. The inclusion of higher order Coulomb interaction terms within current many-body theory is limited by the analytical complexity This work provides valuable experimental observations, which invite further theoretical endeavour within this field. Ultrafast spectroscopic techniques have been used out to investigate both coherent and incoherent exciton dynamics within zinc selenide-based multiple quantum wells. Time-integrated four-wave-mixing experiments were carried out to investigate exciton dephasing due to exciton-phonon scattering. In particular experiments on multiple quantum well structures with a range of well widths demonstrated that exciton-acoustic phonon scattering was found to reach a maximum when the quantum confinement within the well was also maximised. The technique of pump-continuum probe spectroscopy has been enhanced giving improved resolution of absorption d...

  3. THz induced nonlinear absorption in ZnTe

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Jepsen, Peter Uhd

    2015-01-01

    Absorption spectra of ZnTe during strong-field THz interaction are investigated. Bleaching of the difference phonon modes below the fundamental TO mode is observed when field strengths higher than 4 MV/cm are applied.......Absorption spectra of ZnTe during strong-field THz interaction are investigated. Bleaching of the difference phonon modes below the fundamental TO mode is observed when field strengths higher than 4 MV/cm are applied....

  4. Identification of Ag-acceptors in $^{111}Ag^{111}Cd$ doped ZnTe and CdTe

    CERN Document Server

    Hamann, J; Deicher, M; Filz, T; Lany, S; Ostheimer, V; Strasser, F; Wolf, H; Wichert, T

    2000-01-01

    Nominally undoped ZnTe and CdTe crystals were implanted with radioactive /sup 111/Ag, which decays to /sup 111/Cd, and investigated by photoluminescence spectroscopy (PL). In ZnTe, the PL lines caused by an acceptor level at 121 meV are observed: the principal bound exciton (PBE) line, the donor-acceptor pair (DAP) band, and the two-hole transition lines. In CdTe, the PBE line and the DAP band that correspond to an acceptor level at 108 meV appear. Since the intensities of all these PL lines decrease in good agreement with the half-life of /sup 111/Ag of 178.8 h, both acceptor levels are concluded to be associated with defects containing a single Ag atom. Therefore, the earlier assignments to substitutional Ag on Zn- and Cd-lattice sites in the respective II-VI semiconductors are confirmed. The assignments in the literature of the S/sub 1/, S /sub 2/, and S/sub 3/ lines in ZnTe and the X/sub 1//sup Ag/, X/sub 2 //sup Ag//C/sub 1//sup Ag/, and C/sub 2//sup Ag/ lines in CdTe to Ag- related defect complexes are ...

  5. Guided Growth of Horizontal p-Type ZnTe Nanowires.

    Science.gov (United States)

    Reut, Gilad; Oksenberg, Eitan; Popovitz-Biro, Ronit; Rechav, Katya; Joselevich, Ernesto

    2016-08-04

    A major challenge toward large-scale integration of nanowires is the control over their alignment and position. A possible solution to this challenge is the guided growth process, which enables the synthesis of well-aligned horizontal nanowires that grow according to specific epitaxial or graphoepitaxial relations with the substrate. However, the guided growth of horizontal nanowires was demonstrated for a limited number of materials, most of which exhibit unintentional n-type behavior. Here we demonstrate the vapor-liquid-solid growth of guided horizontal ZnTe nanowires and nanowalls displaying p-type behavior on four different planes of sapphire. The growth directions of the nanowires are determined by epitaxial relations between the nanowires and the substrate or by a graphoepitaxial effect that guides their growth along nanogrooves or nanosteps along the surface. We characterized the crystallographic orientations and elemental composition of the nanowires using transmission electron microscopy and photoluminescence. The optoelectronic and electronic properties of the nanowires were studied by fabricating photodetectors and top-gate thin film transistors. These measurements showed that the guided ZnTe nanowires are p-type semiconductors and are photoconductive in the visible range. The guided growth of horizontal p-type nanowires opens up the possibility of parallel nanowire integration into functional systems with a variety of potential applications not available by other means.

  6. Self-Assembled Formation of Well-Aligned Cu-Te Nano-Rods on Heavily Cu-Doped ZnTe Thin Films

    Science.gov (United States)

    Liang, Jing; Cheng, Man Kit; Lai, Ying Hoi; Wei, Guanglu; Yang, Sean Derman; Wang, Gan; Ho, Sut Kam; Tam, Kam Weng; Sou, Iam Keong

    2016-11-01

    Cu doping of ZnTe, which is an important semiconductor for various optoelectronic applications, has been successfully achieved previously by several techniques. However, besides its electrical transport characteristics, other physical and chemical properties of heavily Cu-doped ZnTe have not been reported. We found an interesting self-assembled formation of crystalline well-aligned Cu-Te nano-rods near the surface of heavily Cu-doped ZnTe thin films grown via the molecular beam epitaxy technique. A phenomenological growth model is presented based on the observed crystallographic morphology and measured chemical composition of the nano-rods using various imaging and chemical analysis techniques. When substitutional doping reaches its limit, the extra Cu atoms favor an up-migration toward the surface, leading to a one-dimensional surface modulation and formation of Cu-Te nano-rods, which explain unusual observations on the reflection high energy electron diffraction patterns and apparent resistivity of these thin films. This study provides an insight into some unexpected chemical reactions involved in the heavily Cu-doped ZnTe thin films, which may be applied to other material systems that contain a dopant having strong reactivity with the host matrix.

  7. Numerical study of the influence of ZnTe thickness on CdS/ZnTe solar cell performance.

    OpenAIRE

    Skhouni, Othmane; EL MANOUNI, AHMED; Marí, B.; Ullah, Hanif

    2016-01-01

    At present most of II–VI semiconductor based solar cells use the CdTe material as an absorber film. The simulation of its performance is realized by means of various numerical modelling programs. We have modelled a solar cell based on zinc telluride (ZnTe) thin film as absorber in substitution to the CdTe material, which contains the cadmium element known by its toxicity. The performance of such photovoltaic device has been numerically simulated and the thickness of the absorber layer has bee...

  8. Simple Technique of Bridging Wide Gap in Esophageal Atresia with Tracheoesophageal Fistula - "Surgical Innovation".

    Science.gov (United States)

    Sharma, A K; Mangal, D

    2017-01-01

    The survival of the patients with esophageal atresia an tracheo esophageal fistula is believed to be an epitome of the success of the neonatal surgery. Restoring the continuty of the food pipe by esophagus to esophagus anastomosis is the best option. Preservation of natural esophagus by delayed repair in a wide gap esophageal atresia is a preferred technique worldwide, however such a management required prolonged hospitalization and dedicated nursing care, which is often not available in most of the centres in India. Esophageal substitutes in wide gap requires multiple operations and have long term problems, so remains the last option. I use the technique of oblique anastomosis which had distrinct advantage over circular anastomosis in the management of esophageal atresia1. This techniqe helps in bridging wide gap to some extent & minimal stricture formation.

  9. Mechanical Properties of Semiconductors and Their Alloys

    Science.gov (United States)

    1992-02-01

    centimeters, 3 and must be perfect bulk single crystals. Many semiconductors, alloys in particular, are only grown as thin films on disparate substrates. For...approximation, not due to Harris. Figure 2 is closer to the practical applications our contract is aimed at. We seek a "super- modulus" effect in a thin ...superlattice of CdTe/ ZnTe . In Figure 2, the superlattice consists of alternating monolayers, along the > direction, of CdTe and ZnTe . Interestingly, the

  10. Determination of the deformation state of HgSe / ZnTe layers

    Energy Technology Data Exchange (ETDEWEB)

    Schafer, P.; Berger, H. [Berlin, Humboldt Univ. (Germany). Institut fuer Physik; Schikora, D. [Paderborn, Universitat-Gesamthochschule (Germany). Fachbereich Physik

    1997-02-01

    High-resolution X-ray diffraction is commonly used to measure the misfit strain and to determine the unstrained lattice parameter of epitaxial semiconductor layers assuming tetragonal distortion. A method is developed which links the measured inter-planar spacings to the deformation tensor without assumption of layer symmetry. For the system HgSe on a thick ZnTe buffer layer deposited by MBE on GaAs substrate, the six components of the reciprocal metric tensor of each layer are determined by a least-squares algorithm from a set of reciprocal lattice vectors (137, 553). A principal-axis transformation of the calculated deformation tensor shows that the deformation nearly parallel to the [110] and [1{sup 1}0] directions in the interface plane differs by more than 15 %. This difference is a function of the epilayer thickness and reaches a maximum for layers slightly thicker than the critical thickness.

  11. Photoluminescence characteristics of ZnTe bulk crystal and ZnTe epilayer grown on GaAs substrate by MOVPE

    Science.gov (United States)

    Lü, Hai-Yan; Mu, Qi; Zhang, Lei; Lü, Yuan-Jie; Ji, Zi-Wu; Feng, Zhi-Hong; Xu, Xian-Gang; Guo, Qi-Xin

    2015-12-01

    Excitation power and temperature-dependent photoluminescence (PL) spectra of the ZnTe epilayer grown on (100) GaAs substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structures are of good structural quality due to their sharp bound excitonic emissions and absence of the deep level structural defect-related emissions. Furthermore, in contrast to the ZnTe bulk crystal, although excitonic emissions for the ZnTe epilayer are somewhat weak, perhaps due to As atoms diffusing from the GaAs substrate into the ZnTe epilayer and/or because of the strain-induced degradation of the crystalline quality of the ZnTe epilayer, neither the donor-acceptor pair (DAP) nor conduction band-acceptor (e-A) emissions are observed in the ZnTe epilayer. This indicates that by further optimizing the growth process it is possible to obtain a high-crystalline quality ZnTe heteroepitaxial layer that is comparable to the ZnTe bulk crystal. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120131110006), the Key Science and Technology Program of Shandong Province, China (Grant No. 2013GGX10221), the Key Laboratory of Functional Crystal Materials and Device (Shandong University, Ministry of Education), China (Grant No. JG1401), the National Natural Science Foundation of China (Grant No. 61306113), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91433112), and the Partnership Project for Fundamental Technology Researches of the Ministry of Education, Culture, Sports, Science and Technology, Japan.

  12. The Three-Dimensional Velocity Distribution of Wide Gap Taylor-Couette Flow Modelled by CFD

    Directory of Open Access Journals (Sweden)

    David Shina Adebayo

    2016-01-01

    Full Text Available A numerical investigation is conducted for the flow between two concentric cylinders with a wide gap, relevant to bearing chamber applications. This wide gap configuration has received comparatively less attention than narrow gap journal bearing type geometries. The flow in the gap between an inner rotating cylinder and an outer stationary cylinder has been modelled as an incompressible flow using an implicit finite volume RANS scheme with the realisable k-ε model. The model flow is above the critical Taylor number at which axisymmetric counterrotating Taylor vortices are formed. The tangential velocity profiles at all axial locations are different from typical journal bearing applications, where the velocity profiles are quasilinear. The predicted results led to two significant findings of impact in rotating machinery operations. Firstly, the axial variation of the tangential velocity gradient induces an axially varying shear stress, resulting in local bands of enhanced work input to the working fluid. This is likely to cause unwanted heat transfer on the surface in high torque turbomachinery applications. Secondly, the radial inflow at the axial end-wall boundaries is likely to promote the transport of debris to the junction between the end-collar and the rotating cylinder, causing the build-up of fouling in the seal.

  13. High resistivity In-doped ZnTe: electrical and optical properties

    Indian Academy of Sciences (India)

    insulating ZnTe prepared by In doping during Bridgman growth was found to have a resistivity of 5.74 × 107 ohm-cm, the highest reported so far in ZnTe, with ... Possible models for semi-insulating behaviour and meta-stability are proposed.

  14. Radiation resistance of wide-gap materials as exemplified by SiC nuclear radiation detectors

    Science.gov (United States)

    Ivanov, A. M.; Strokan, N. B.; Lebedev, A. A.

    2012-04-01

    In wide-gap materials used in nuclear detectors, the polarization effect is typically observed when the concentration of radiation-induced defects is high. An emf arising in the detector is associated with long-term trapping of charge carries by deep radiation-induced levels (centers). The polarization kinetics and the polarization field strength are determined experimentally. The trapping efficiency can be controlled by varying the temperature, and a tradeoff can be reached at an "optimal" temperature between the generation current and the position of the deepest level, which has a negligible effect on charge losses via trapping. It is found that the ratio between the depth of this level and the bandgap is about 1/3 irrespective of the material but the optimal temperature is material-specific.

  15. Compound Semiconductor Radiation Detectors

    CERN Document Server

    Owens, Alan

    2012-01-01

    Although elemental semiconductors such as silicon and germanium are standard for energy dispersive spectroscopy in the laboratory, their use for an increasing range of applications is becoming marginalized by their physical limitations, namely the need for ancillary cooling, their modest stopping powers, and radiation intolerance. Compound semiconductors, on the other hand, encompass such a wide range of physical and electronic properties that they have become viable competitors in a number of applications. Compound Semiconductor Radiation Detectors is a consolidated source of information on all aspects of the use of compound semiconductors for radiation detection and measurement. Serious Competitors to Germanium and Silicon Radiation Detectors Wide-gap compound semiconductors offer the ability to operate in a range of hostile thermal and radiation environments while still maintaining sub-keV spectral resolution at X-ray wavelengths. Narrow-gap materials offer the potential of exceeding the spectral resolutio...

  16. Excitonic surface polaritons in luminescence from ZnTe crystals

    Energy Technology Data Exchange (ETDEWEB)

    Brodin, M.S.; Bandura, V.M.; Matsko, M.G. (AN Ukrainskoj SSR, Kiev. Inst. Fiziki)

    1984-10-01

    The form and structure of reflection and exciton-polariton luminescence spectra of ZnTe crystals are studied in the region of the ground (n = 1) exciton state. The longitudinal-transverse splitting magnitude ..delta..E/sub LT/ is determined from the shape of the reflection spectra. A detected doublet structure of an emission band from the lower polariton branch is associated with the k-linear term. The evolution of bulk and surface polariton luminescence spectra versus temperature and wavelength of the exciting light is investigated.

  17. A ZnTe Thin Film Memory Device

    OpenAIRE

    Marc Burgelman

    1980-01-01

    Thin ZnTe layers show memory switching characteristics. The electrical conduction in the non-ohmic off-state is shown to be due to Poole–Frenkel emission. An electrothermal model is proposed to explain the off-on transition; this model is confirmed by experiments. The characteristics of metal–ZnTe–metal sandwich structure as a memory device are investigated. The switching parameters are stable during a series of switching events, but the rather poor write–erase lifetime (200 cycles) still con...

  18. Structural properties of perfect ZnTe epilayers on (001) GaAs substrates

    Energy Technology Data Exchange (ETDEWEB)

    Lang, M. (ForschungsInst. fuer Optoelektronik, Univ. Linz (Austria)); Schikora, D.; Widmer, T. (and others)

    1994-04-14

    We report on molecular beam epitaxy and hot-wall beam epitaxy growth of ZnTe epilayers on (001) GaAs substrates. The surface reconstruction of (001) ZnTe is measured by reflection high-energy electron diffraction (RHEED). The RHEED pattern as a function of the beam equivalent pressure ratio p[sub Te]/p[sub Zn] and substrate temperature is studied. Mosaic structures of the ZnTe epilayers grown under optimized conditions are investigated quantitatively by high resolution X-ray diffraction and photoluminescence. These data, which are related to the three-dimensional perfection of epilayers, are contrasted to RHEED measurements of the surface morphology

  19. Optical Properties and Surface morphology of ZnTe thin films prepared by multiple potential steps

    OpenAIRE

    Gromboni, Murilo F.; Lucas,Francisco W. S.; Mascaro,Lucia H.

    2014-01-01

    In this work, the ZnTe thin films were electrodeposited using potentiostatic steps, on Pt substrate. The effect of steps number, the deposition time for each element (Zn or Te) and layer order (Zn/Te or Te/Zn) in the morphology, composition, band gap energy and photocurrent was evaluated. Microanalysis data showed that the ratio Zn/Te ranged from 0.12 and 0.30 and the film was not stoichiometric. However, the band-gap value obtained from in all experimental conditions used in this work was 2....

  20. Wide-gap large spark chamber supplying by high-voltage radio pulse

    Energy Technology Data Exchange (ETDEWEB)

    Asatiani, T.L.; Alchudzhyan, S.V.; Kozliner, L.I.; Martirosyan, G.S. (Erevanskij Fizicheskij Inst. (USSR))

    In the process of avalanche formation in wide-gap (2 gaps 15 cm each) spark chambers when supplying them by high-voltage pulse (field intensity is 5.7-7.0 kV/cm, pulse duration-250-150 ns) of unipolar shape, a directed drift of charges in electric field takes place, which results in the shift of the track photographed as to actual particle trajectory. To decrease the shift in the process of chamber supply a high-voltage radio pulse was used, which presented an attenuating sinusoid. When supplying the chamber by sign-alternating pulse the shift constitutes 0.16+-0.15 mm, and the angle - 5.3x10/sup -5/+- 1.1x10/sup -3/ rad. When supplying by unipolar pulse the shift equals O.58+-0.40 mm, and the angle - 1.5x10/sup -4/+-2.5x10/sup -3/ rad. The use of sign-alternating supply permitted to increase the accuracy of track localization and to decrease the dependence of track brightness on the angle of particle entrance to the chamber.

  1. Influence of complex impurity centres on radiation damage in wide-gap metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Lushchik, A., E-mail: aleksandr.lushchik@ut.ee [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Lushchik, Ch. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Popov, A.I. [Institute of Solid State Physics, University of Latvia, Kengaraga 8, Riga LV-1063 (Latvia); Schwartz, K. [GSI Helmholtzzentrum für Schwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt (Germany); Shablonin, E.; Vasil’chenko, E. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia)

    2016-05-01

    Different mechanisms of radiation damage of wide-gap metal oxides as well as a dual influence of impurity ions on the efficiency of radiation damage have been considered on the example of binary ionic MgO and complex ionic–covalent Lu{sub 3}Al{sub 5}O{sub 12} single crystals. Particular emphasis has been placed on irradiation with ∼2 GeV heavy ions ({sup 197}Au, {sup 209}Bi, {sup 238}U, fluence of 10{sup 12} ions/cm{sup 2}) providing extremely high density of electronic excitations within ion tracks. Besides knock-out mechanism for Frenkel pair formation, the additional mechanism through the collapse of mobile discrete breathers at certain lattice places (e.g., complex impurity centres) leads to the creation of complex defects that involve a large number of host atoms. The experimental manifestations of the radiation creation of intrinsic and impurity antisite defects (Lu|{sub Al} or Ce|{sub Al} – a heavy ion in a wrong cation site) have been detected in LuAG and LuAG:Ce{sup 3+} single crystals. Light doping of LuAG causes a small enhancement of radiation resistance, while pair impurity centres (for instance, Ce|{sub Lu}–Ce|{sub Al} or Cr{sup 3+}–Cr{sup 3+} in MgO) are formed with a rise of impurity concentration. These complex impurity centres as well as radiation-induced intrinsic antisite defects (Lu|{sub Al} strongly interacting with Lu in a regular site) tentatively serve as the places for breathers collapse, thus decreasing the material resistance against dense irradiation.

  2. Optical properties and surface morphology of ZnTe thin films prepared by multiple potential steps

    Energy Technology Data Exchange (ETDEWEB)

    Gromboni, Murilo F.; Lucas, Francisco W. S.; Mascaro, Lucia H., E-mail: lmascaro@ufscar.br [Universidade de Federal de Sao Carlos (LIEC/UFSCar), SP (Brazil). Departamento de Quimica. Lab. de Eletroquimica e Ceramica

    2014-03-15

    In this work, the ZnTe thin films were electrodeposited using potentiostatic steps, on Pt substrate. The effect of steps number, the deposition time for each element (Zn or Te) and layer order (Zn/Te or Te/Zn) in the morphology, composition, band gap energy and photocurrent was evaluated. Microanalysis data showed that the ratio Zn/Te ranged from 0.12 and 0.30 and the film was not stoichiometric. However, the band-gap value obtained from in all experimental conditions used in this work was 2.28 eV, indicating film growth of ZnTe. The samples with higher Zn showed higher photocurrent, which was of the order of 2.64 μA cm{sup -2} and dendritic morphology (author)

  3. Large scale ZnTe nanostructures on polymer micro patterns via capillary force photolithography

    Energy Technology Data Exchange (ETDEWEB)

    Florence, S. Sasi, E-mail: sshanmugaraj@jazanu.edu.sa; Can, N.; Adam, H. [Department of Physics, Jazan University, Jizan-114 (Saudi Arabia); Sachan, P.; Gupta, R. K. [DST-Unit on Nanosciences, Indian Institute of Technology, Kanpur (India); Arockiasamy, L. [King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451 (Saudi Arabia); Umadevi, M. [Department of Physics, Mother Teresa Women’s University, Kodaikanal-624101 (India)

    2016-06-10

    A novel approach to prepare micro patterns ZnTe nanostructures on Si (100) substrate using thermal evaporation is proposed by capillary Force Lithography (CFL) technique on a self-assembled sacrificial Polystyrene mask. Polystyrene thin films on Si substrates are used to fabricate surface micro-relief patterns. ZnTe nanoparticles have been deposited by thermal evaporation method. The deposited ZnTe nanoparticles properties were assessed by Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM). SEM studies indicated that the particles are uniform in size and shape, well dispersed and spherical in shape. This study reports the micro-arrays of ZnTe nanoparticles on a self-assembled sacrificial PS mask using a capillary flow photolithography process which showed excellent, morphological properties which can be used in photovoltaic devices for anti-reflection applications.

  4. Effect of Cr-Doping on Optical Properties of ZnTe Thin Films

    Science.gov (United States)

    Sharma, Dinesh C.; Garima, Srivastava, Subodh; Vijay, Y. K.; Sharma, Y. K.

    2011-07-01

    The chromium doped zinc telluride (ZnTe:Cr) as well as ZnTe thin films and their sandwich structures were prepared onto glass substrate by thermal evaporation method under the vacuum of 10-5 torr . Thickness of these thin films is determined by ellipsometric measurements. The optical absorbance and transmittance is found to decrease with increase in chromium concentration into ZnTe thin films. Surface topography of these films has been done by optical microscopy.

  5. Isothermal close space sublimation for II-VI semiconductor filling of porous matrices

    Science.gov (United States)

    2012-01-01

    Isothermal close space sublimation, a simple and low-cost physical vapour transport technique, was used to infiltrate ZnTe and CdSe semiconductors in porous silicon. The structure of the embedded materials was determined by X-ray diffraction analysis while Rutherford backscattering spectra allowed determining the composition profiles of the samples. In both cases, a constant composition of the II-VI semiconductors throughout the porous layer down to the substrate was found. Resonance Raman scattering of the ZnTe samples indicates that this semiconductor grows in nanostructured form inside the pores. Results presented in this paper suggest that isothermal close space sublimation is a promising technique for the conformal growth of II-VI semiconductors in porous silicon. PMID:22823959

  6. Fundamentals of semiconductor lasers

    CERN Document Server

    Numai, Takahiro

    2015-01-01

    This book explains physics under the operating principles of semiconductor lasers in detail based on the experience of the author, dealing with the first manufacturing of phase-shifted DFB-LDs and recent research on transverse modes.   The book also bridges a wide gap between journal papers and textbooks, requiring only an undergraduate-level knowledge of electromagnetism and quantum mechanics, and helps readers to understand journal papers where definitions of some technical terms vary, depending on the paper. Two definitions of the photon density in the rate equations and two definitions of the phase-shift in the phase-shifted DFB-LD are explained, and differences in the calculated results are indicated, depending on the definitions.    Readers can understand the physics of semiconductor lasers and analytical tools for Fabry-Perot LDs, DFB-LDs, and VCSELs and will be stimulated to develop semiconductor lasers themselves.

  7. Intensity enhancement of Te Raman modes by laser damage in ZnTe epilayers

    Science.gov (United States)

    Larramendi, E. M.; Berth, G.; Wiedemeier, V.; Hüsch, K.-P.; Zrenner, A.; Woggon, U.; Tschumak, E.; Lischka, K.; Schikora, D.

    2010-07-01

    Damage caused by laser irradiation on the surface of ZnTe epilayers was studied by micro-Raman and atomic force microscopy (AFM). ZnTe LO-phonon overtones up to four order and TO + (n - 1)LO zone-center phonons were observed in the resonant micro-Raman spectra at room temperature. Discrepancies in the literature regarding the origin of two features observed at low frequencies around 120 and 140 cm-1 in the Raman spectrum of ZnTe are discussed and resolved. These Raman peaks were not detected by using a low excitation laser power density on a Zn-terminated ZnTe surface; however, with the increase of the laser power density they were found to arise irreversibly. The correspondence of these peaks in a wave number with the strongest Raman peaks of the crystalline tellurium phase and the intensity enhancement behavior with the laser power in a similar way as for CdTe strongly suggests the formation of crystalline tellurium aggregates on the layer surface due to laser irradiation damage. AFM data reveal the occurrence of laser ablation on the ZnTe surface even though the surface temperature of the sample is below the melting point.

  8. Growth and Crystal Orientation of ZnTe on m-Plane Sapphire with Nanofaceted Structure

    Science.gov (United States)

    Nakasu, Taizo; Sun, Wei-Che; Kobayashi, Masakazu; Asahi, Toshiaki

    2017-04-01

    ZnTe thin films on sapphire substrate with nanofaceted structure have been studied. The nanofaceted structure of the m-plane (10-10) sapphire was obtained by heating the substrate at above 1100°C in air, and the r-plane (10-12) and S-plane (1-101) were confirmed. ZnTe layers were prepared on the nanofaceted m-plane sapphire substrates by molecular beam epitaxy (MBE). The effect of the nanofaceted structure on the orientation of the thin films was examined based on x-ray diffraction (XRD) pole figures. Transmission electron microscopy (TEM) was also employed to characterize the interface structures. The ZnTe layer on the nanofaceted m-plane sapphire substrate exhibited (331)-plane orientation, compared with (211)-plane without the nanofaceted structure. After thermal treatment, the m-plane surface vanished and (211) layer could not be formed because of the lack of surface lattice matching. On the other hand, (331)-plane thin film was formed on the nanofaceted m-plane sapphire substrate, since the (111) ZnTe domains were oriented on the S-facet. The orientation of the ZnTe epilayer depended on the atomic ordering on the surface and the influence of the S-plane.

  9. Synthesis and characterization of small size fluorescent LEEH caped blue emission ZnTe quantum dots

    Directory of Open Access Journals (Sweden)

    Patnaik Sumanta Kumar

    2017-04-01

    Full Text Available We report here for the first time the synthesis of LEEH caped very small size (2 nm ZnTe quantum dots at low temperature (less than 100 °C using a simple chemical route. The effects of aging and stirring time on the absorption spectra of the quantum dots were investigated. The synthesized nanocrystal (NC was characterized by PL, TEM, XRD and the formation of very small size quantum dots having FCC structure was confirmed. Further, blue emission from the prepared sample was observed during exposure to monochromatic UV radiation. ZnTe NCs obtained in this study were found to be more stable compared to those presented in literature reports. ZnTe NCs may be considered as a new material in place of CdTe for optoelectronics devices.

  10. (211) oriented ZnTe growth on m-plane sapphire by MBE

    Energy Technology Data Exchange (ETDEWEB)

    Nakasu, Taizo [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kobayashi, Masakazu [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26, Tokyo 169-0051 (Japan); Togo, Hiroyoshi [NTT Microsystem Integration Laboratories, Atugi-shi 243-0198 (Japan); Asahi, Toshiaki [Technology Development Center, JX Nippon Mining and Metals Corporation, Hitachi-shi 317-0056 (Japan)

    2013-11-15

    Single-crystalline and single domain ZnTe thin films are sought for high-performance terahertz wave detectors, and ZnTe/sapphire heterostructures were considered since the Electro-Optical (EO) effect could be obtained only from epilayers. ZnTe epilayers were grown on m-plane sapphire substrates by molecular beam epitaxy, and the potential of single domain epilayers was explored. Through the X-ray diffraction pole figure measurement it was confirmed that one (100) oriented ZnTe domain along with two kinds of (211) oriented domains were formed on the m-plane sapphire when the layer was grown at 340 C. When the layer was grown at 350 C, the (211) oriented domain dominated the film. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Intrinsic defect complexes in CdTe and ZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, A., E-mail: alexandra.carvalho@epfl.ch [Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne (Switzerland); Oberg, S. [Department of Mathematics, Lulea University of Technology, Lulea S-97187 (Sweden); Briddon, P.R. [School of Natural Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU (United Kingdom)

    2011-08-31

    Radiation defects in CdTe and ZnTe are modeled from first principles. The most important intrinsic defects resulting from cation evaporation or displacement are cation vacancies and tellurium anti-sites, electrically active defects characterized by a low formation energy. The reactions between those two defects are investigated. Since cation vacancy clusters of less than four vacancies are not stable, it is argued that cation vacancy aggregation is not a dominant process in near-equilibrium conditions. In-grown or radiation-induced clusters of four cation vacancies may serve as a nucleation center for tellurium precipitation. The formation energy of these small voids is lower in ZnTe than in CdTe. Additionally, cation-anion divacancies are stable in ZnTe and in p-type CdTe.

  12. ZnTe :O phosphor development for x-ray imaging applications

    Science.gov (United States)

    Kang, Z. T.; Summers, C. J.; Menkara, H.; Wagner, B. K.; Durst, R.; Diawara, Y.; Mednikova, G.; Thorson, T.

    2006-03-01

    An efficient ZnTe :O x-ray powder phosphor was prepared by a dry synthesis process using gaseous doping and etching medias. The x-ray luminescent properties were evaluated and compared to standard commercial phosphors exhibited an x-ray luminescent efficiency equivalent to 76% of Gd2O2S:Tb and an equal resolution of 2.5lines/mm. In addition, the fast decay time, low afterglow, and superior spectral match to conventional charge-coupled devices-indicate that ZnTe :O is a very promising phosphor candidate for x-ray imaging applications.

  13. The synthesis of large-diameter ZnTe crystal for THz emitting and detection

    Science.gov (United States)

    Liu, Hang; Bai, Wei; Feng, Jiatai; Jie, Wanqi

    2017-10-01

    A high-quality, large-size ZnTe ingot with the diameter of 60 mm and the length of 80 mm were prepared by the modified temperature gradient solvent method, where the Te rich solution acted as both solubility promoter and reactant. Using this method, the crystallization temperature was reduced from 1568 K to 1333 K, plus, the crystal defects could be reduced in some extent due to the lower zinc partial pressure. Few Te inclusions are found in the as-grown ZnTe crystal with the bulk factor less than 0.1%. X-ray diffraction (XRD), infrared transmission microscope, fourier transform infrared (FT-IR) spectrometer, ultraviolet-visible (UV-Vis) spectrophotometer were used to analyze the qualities and properties of the ZnTe crystals. The infrared transmittance over the wavenumber range from 500 to 4000 cm-1 is about 60% and the band gap is about 2.23 eV at the room temperature. The FWHM of the detection pulse with the THz time-domain spectroscopy (THz-TDS) is about 0.34 ps. Besides, both the radiation and detection pulse have a wide frequency distribution about 3 THz at the room temperature. These results strongly indicate that the high-quality ZnTe crystal synthesized by the temperature gradient solvent method is superior for THz device applications.

  14. High resistivity In-doped ZnTe: electrical and optical properties

    Indian Academy of Sciences (India)

    Unknown

    Semi-insulating ZnTe prepared by In doping during Bridgman growth was found to have a resistivity of 5⋅74 × 107 ohm-cm, ... Thermally stimulated current (TSC) studies revealed 2 trap levels at depths of 202–222 meV and ... Possible models for semi-insulating behaviour and meta-stability are proposed. Keywords.

  15. Defect properties of Sn- and Ge-doped ZnTe: suitability for intermediate-band solar cells

    Science.gov (United States)

    Flores, Mauricio A.

    2018-01-01

    We investigate the electronic structure and defect properties of Sn- and Ge- doped ZnTe by first-principles calculations within the DFT+GW formalism. We find that ({{{Sn}}}{{Zn}}) and ({{{Ge}}}{{Zn}}) introduce isolated energy levels deep in the band gap of ZnTe, derived from Sn-5s and Ge-4s states, respectively. Moreover, the incorporation of Sn and Ge on the Zn site is favored in p-type ZnTe, in both Zn-rich and Te-rich environments. The optical absorption spectra obtained by solving the Bethe–Salpeter equation reveals that sub-bandgap absorptance is greatly enhanced due to the formation of the intermediate band. Our results suggest that Sn- and Ge-doped ZnTe would be a suitable material for the development of intermediate-band solar cells, which have the potential to achieve efficiencies beyond the single-junction limit.

  16. Unprecedented Integral-Free Debye Temperature Formulas: Sample Applications to Heat Capacities of ZnSe and ZnTe

    National Research Council Canada - National Science Library

    R. Pässler

    2017-01-01

    Detailed analytical and numerical analyses are performed for combinations of several complementary sets of measured heat capacities, for ZnSe and ZnTe, from the liquid-helium region up to 600 K. The isochoric (harmonic...

  17. Surface Texture and Crystallinity Variation of ZnTe Epilayers Grown on the Step-Terrace Structure of the Sapphire Substrate

    Science.gov (United States)

    Nakasu, Taizo; Kizu, Takeru; Yamashita, Sotaro; Aiba, Takayuki; Hattori, Shota; Sun, Wei-Che; Taguri, Kosuke; Kazami, Fukino; Hashimoto, Yuki; Ozaki, Shun; Kobayashi, Masakazu; Asahi, Toshiaki

    2016-04-01

    ZnTe/sapphire heterostructures were focused, and ZnTe thin films were prepared on highly mismatched sapphire substrates by molecular beam epitaxy. A sapphire substrate possessing an atomically-smooth step-terrace structure was used to improve the crystallinity and morphology of the produced ZnTe film. The growth mode of the ZnTe thin film on a sapphire substrate with an atomically-smooth step-terrace structure was found to shift to a two-dimensional growth mode, and a ZnTe thin film possessing a flat surface was obtained. The crystallographic properties of the ZnTe film suggested that the resulting layer consisted of a single (111)-oriented domain. The photoluminescence property was also improved, and the interface lattice alignment between the ZnTe and sapphire was also affected by the atomically-smooth step-terrace structure.

  18. Aluminum diffusion in ZnTe films grown on GaSb substrates for n-type doping

    Energy Technology Data Exchange (ETDEWEB)

    DiNezza, Michael J.; Zhang, Qiang; Ding, Ding; Zhang, Yong-Hang [Center for Photonics Innovation, Arizona State University, Tempe, AZ (United States); School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ (United States); Fan, Jin [Center for Photonics Innovation, Arizona State University, Tempe, AZ (United States); Department of Physics, Arizona State University, Tempe, AZ (United States); Liu, Xinyu; Furdyna, Jacek K. [Department of Physics, University of Notre Dame, Notre Dame, IN (United States)

    2012-08-15

    ZnTe PN homojunctions are fabricated using thermal diffusion of Al into a ZnTe film grown on lattice-matched GaSb substrates by molecular beam epitaxy. Rectifying J-V characteristics and the photovoltaic effect are observed which suggests that n-type ZnTe has been successfully achieved. The reverse bias breakdown voltage is found to be dependent on annealing condition and acceptor concentration, and the trend agrees with PN junction theory. Secondary ion mass spectrometer depth profiles of the Al film show that Zn and Te out-diffuse into the Al film during annealing. This out-diffusion is undesirable because it may result in Zn vacancies which compensate Al donor atoms. Photoluminescence measurements of annealed ZnTe samples without the Al diffusion layer show strong band-edge luminescence at room temperature. Midgap luminescence also appears for annealed samples but the intensity is lower than the band-edge peak. This technique may lead to a better understanding of the n-type doping problem for ZnTe, and could lead to in-situdoping techniques and treatments. Successful n-type doping of ZnTe with low resistivity will enable high-efficiency optoelectronic devices operating at pure-green wavelengths (550 nm) (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Acceptors in II-IV Semiconductors - Incorporation and Complex Formation

    CERN Multimedia

    2002-01-01

    A strong effort is currently devoted to the investigation of defects and the electrical activation of dopant atoms in II-VI semiconductors. In particular, the knowledge about the behaviour of acceptors, prerequisite for the fabrication of p-type semiconductors, is rather limited. The perturbed $\\,{\\gamma\\gamma}$ -angular correlation technique (PAC) and the photoluminescence spectroscopy (PL) using the radioactive isotopes $^{77}\\!$Br and $^{111}\\!$Ag will be applied for investigating the behaviour of acceptor dopant atoms and their interactions with defects in II-VI semiconductors. The main topic will be the identification of the technical conditions for the incorporation of electrically active acceptors in the II-VI semiconductors ~ZnS, ZnSe, ZnTe, CdS, CdSe, and CdTe with particular emphasis on the compounds~ CdTe, ZnSe, and ZnTe. The investigations will be supplemented by first exploratory PL experiments with the group V acceptors $^{71}\\!$As and $^{121}\\!$Sb. With help of the probe $^{111}\\!$Ag, the pos...

  20. Growth and optical properties of CdTe quantum dots in ZnTe nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Wojnar, Piotr; Janik, Elzbieta; Baczewski, Lech T.; Kret, Slawomir; Karczewski, G.; Wojtowicz, Tomasz [Institute of Physics, Polish Academy of Sciences, Al Lotnikow 32/46, 02-668 Warsaw (Poland); Goryca, Mateusz; Kazimierczuk, Tomasz; Kossacki, Piotr [Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul Hoza 69, 00-681 Warsaw (Poland)

    2011-09-12

    We report on the formation of optically active CdTe quantum dots in ZnTe nanowires. The CdTe/ZnTe nanostructures have been grown by a gold nanocatalyst assisted molecular beam epitaxy in a vapor-liquid solid growth process. The presence of CdTe insertions in ZnTe nanowire results in the appearance of a strong photoluminescence band in the 2.0 eV-2.25 eV energy range. Spatially resolved photoluminescence measurements reveal that this broad emission consists of several sharp lines with the spectral width of about 2 meV. The large degree of linear polarization of these individual emission lines confirms their nanowire origin, whereas the zero-dimensional confinement is proved by photon correlation spectroscopy.

  1. Better band gaps for wide-gap semiconductors from a locally corrected exchange-correlation potential that nearly eliminates self-interaction errors

    Science.gov (United States)

    Singh, Prashant; Harbola, Manoj K.; Johnson, Duane D.

    2017-10-01

    This work constitutes a comprehensive and improved account of electronic-structure and mechanical properties of silicon-nitride (Si3 N4 ) polymorphs via van Leeuwen and Baerends (LB) exchange-corrected local density approximation (LDA) that enforces the exact exchange potential asymptotic behavior. The calculated lattice constant, bulk modulus, and electronic band structure of Si3 N4 polymorphs are in good agreement with experimental results. We also show that, for a single electron in a hydrogen atom, spherical well, or harmonic oscillator, the LB-corrected LDA reduces the (self-interaction) error to exact total energy to  ∼10%, a factor of three to four lower than standard LDA, due to a dramatically improved representation of the exchange-potential.

  2. The Role of Work Function and Band Gap in Resistive Switching Behaviour of ZnTe Thin Films

    Science.gov (United States)

    Rowtu, Srinu; Sangani, L. D. Varma; Krishna, M. Ghanashyam

    2017-12-01

    Resistive switching behavior by engineering the electrode work function and band gap of ZnTe thin films is demonstrated. The device structures Au/ZnTe/Au, Au/ZnTe/Ag, Al/ZnTe/Ag and Pt/ZnTe/Ag were fabricated. ZnTe was deposited by thermal evaporation and the stoichiometry and band gap were controlled by varying the source-substrate distance. Band gap could be varied between 1.0 eV to approximately 4.0 eV with the larger band gap being attributed to the partial oxidation of ZnTe. The transport characteristics reveal that the low-resistance state is ohmic in nature which makes a transition to Poole-Frenkel defect-mediated conductivity in the high-resistance states. The highest R off-to-R on ratio achieved is 109. Interestingly, depending on stoichiometry, both unipolar and bipolar switching can be realized.

  3. Using the Semiconductors Materials of InSb-ZnTe System in Sensors for Gas Control

    Science.gov (United States)

    Shubenkova, E. G.

    2017-04-01

    The samples of thin film semiconductor compounds InSb, ZnTe and solid solutions based on them were obtained by vapor deposition of components on a dielectric substrate in a vacuum, followed by annealing and their surface properties in CO, O2 and NH3 gas atmospheres were investigated. Identification of the samples was carried out by X-ray diffraction techniques. In the temperature range 253 ÷ 403 K and a pressure range of 1÷12 Pa the gas adsorption was measured by piezoelectric microbalance technique. In order to establish the basic regularities of processes flowing on samples surface in addition to the electrophisical were used Infrared and Raman spectroscopic measurements. The resulting addiction “surface property - composition” is extreme and have allowed to determine solid solution InSb0,95-ZnTe0,05 as the most sensitive to the presence of ammonia, selective and this sample exhibits a negligible oxidation of surface.

  4. Polycrystalline ZnTe thin film on silicon synthesized by pulsed laser deposition and subsequent pulsed laser melting

    Science.gov (United States)

    Xu, Menglei; Gao, Kun; Wu, Jiada; Cai, Hua; Yuan, Ye; Prucnal, S.; Hübner, R.; Skorupa, W.; Helm, M.; Zhou, Shengqiang

    2016-03-01

    ZnTe thin films on Si substrates have been prepared by pulsed laser deposition and subsequent pulsed laser melting (PLM) treatment. The crystallization during PLM is confirmed by Raman scattering, x-ray diffraction and room temperature photoluminescence (PL) measurements. The PL results show a broad peak at 574 nm (2.16 eV), which can be assigned to the transitions from the conduction band to the acceptor level located at 0.145 eV above the valence band induced by zinc-vacancy ionization. Our work provides an applicable approach to low temperature preparation of crystalline ZnTe thin films.

  5. Ag doped ZnTe films prepared by closed space sublimation and an ion exchange process

    Energy Technology Data Exchange (ETDEWEB)

    Aqili, Akram K.S., E-mail: akramaq@hu.edu.jo [Department of Physics, Hashemite University, Zarqa (Jordan); Saleh, Ahmad J. [Department of Physics, Hashemite University, Zarqa (Jordan); Ali, Zulfiqar [Optics Laboratories, Islamabad (Pakistan); Al-Omari, S. [Department of Physics, Hashemite University, Zarqa (Jordan)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer ZnTe thin films are prepared by low-cost simple technique (CSS). Black-Right-Pointing-Pointer Silver doping is achieved by an ion exchange process. Black-Right-Pointing-Pointer Small peaks appear in the XRD diffraction pattern related to Ag{sub 2}Te. Black-Right-Pointing-Pointer Increase of the films refractive index and shift of optical band was observed. - Abstract: ZnTe thin films were deposited by closed space sublimation (CSS) technique on amorphous glass substrate. The deposited films were immersed in AgNO{sub 3} solution for different time periods, then heated in vacuum. The resistivity of the film, immersed for 30 min, was reduced by less than six orders of magnitudes. The films structures were characterized by X-ray diffraction (XRD). Atomic force microscope (AFM) was used to detect the surface morphology of the films. The films thickness, the optical properties, such as refractive index, absorption coefficient and the optical band gap were determined from transmittance spectra in the wavelength range of 400-2500 nm. The dark electrical conductivities of the films were studied as function of temperature to determine the conductivity activation energy.

  6. Sensing application of an optical fiber dip coated with L-Cystein ethyl ester hydrochloride capped ZnTe quantum dots

    Directory of Open Access Journals (Sweden)

    Sundaray Madhulita

    2016-09-01

    Full Text Available Optical fiber in conjunction with ZnTe quantum dots (QDs is investigated for sensing application. ZnTe QDs, are synthesized by a simple chemical bottom up approach. Quantum dots are capped with L-Cystein ethyl ester hydrochloride (LEEH, to increase their stability. Then LEEH capped ZnTe QDs, whose size is estimated as 2.29 nm by effective mass approximation (EMA, are dip-coated on a cladding removed optical fiber. Different concentrations of alcohol and ammonia are used to investigate the sensing behavior. It is found that sensitivity of the sensor increases with the use of QDs for both alcohol and ammonia.

  7. Substrate temperature dependence of ZnTe epilayers grown on GaAs(0 0 1) by molecular beam epitaxy

    Science.gov (United States)

    Zhao, Jie; Zeng, Yiping; Liu, Chao; Li, Yanbo

    2010-04-01

    ZnTe thin films have been grown on GaAs(0 0 1) substrates at different temperatures with constant Zn and Te beam equivalent pressures (BEPs) by molecular beam epitaxy (MBE). In situ reflection high-energy electron diffraction (RHEED) observation indicates that two-dimensional (2D) growth mode can be established after around one-minute three-dimensional (3D) nucleation by increasing the substrate temperature to 340 °C. We found that Zn desorption from the ZnTe surface is much greater than that of Te at higher temperatures, and estimated the Zn sticking coefficient by the evolution of growth rate. The Zn sticking coefficient decreases from 0.93 to 0.58 as the temperature is elevated from 320 to 400 °C. The ZnTe epilayer grown at 360 °C displays the narrowest full-width at half-maximum (FWHM) of 660 arcsec from (0 0 4) reflection in double-crystal X-ray rocking curve (DCXRC) measurements. The surface morphology of ZnTe epilayers is strongly dependent on the substrate temperature, and the root-mean-square (RMS) roughness diminishes drastically with the increase in temperature.

  8. Semiconductor physics

    Energy Technology Data Exchange (ETDEWEB)

    Tuchkevich, V.M.; Frenkel, V.Y.

    1986-01-01

    This text is a collection of papers devoted mainly to the results of the research work in the field of semiconductors. Topics include photovoltaic solar energy conversion, interacting excitons in germanium and silicon, chalcogenide vitreous semiconductors, optical cooling of the nuclear spin system in a semiconductor, photon drag of electrons in semiconductors, dielectric losses in crystals, light scattering from heavily doped semiconductors, and the capacity of an abrupt asymmetric p-n junction.

  9. Self-Assembled Formation of Well-Aligned Cu-Te Nano-Rods on Heavily Cu-Doped ZnTe Thin Films

    National Research Council Canada - National Science Library

    Liang, Jing; Cheng, Man Kit; Lai, Ying Hoi; Wei, Guanglu; Yang, Sean Derman; Wang, Gan; Ho, Sut Kam; Tam, Kam Weng; Sou, Iam Keong

    2016-01-01

    ... reported. We found an interesting self-assembled formation of crystalline well-aligned Cu-Te nano-rods near the surface of heavily Cu-doped ZnTe thin films grown via the molecular beam epitaxy technique...

  10. The p-type doping of vacuum deposited ZnTe thin films with bismuth by a new technique of using nano-spheres

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Gowrish K., E-mail: kgowrishrao@gmail.com [Department of Physics, Manipal Institute of Technology, Manipal 576104, Karnataka (India); Shivakumar, G.K.; Kasturi, V.B. [Thin Film Laboratory, Department of Physics, National Institute of Technology Karnataka Surathkal Srinivasnagar, Mangalore 575025, Karnataka (India)

    2010-11-25

    The present paper reports the successful doping of vacuum evaporated zinc telluride (ZnTe) thin films with bismuth by a new technique of using nano-spheres. The discontinuous films of bismuth (the dopant material), containing bismuth in the form of nano-spheres, were prepared by vacuum evaporation and the ZnTe films were then deposited on top of them. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used to ascertain the formation of discontinuous bismuth films and the proper diffusion of bismuth in ZnTe films, respectively. After doping, the carrier concentration of the ZnTe films was found to increase by an order of the magnitude. The electrical conductivity also improved significantly. The photoconductivity and photo-response properties of the doped films were also analysed.

  11. Three-dimensional numerical simulation of a continuously rotating detonation in the annular combustion chamber with a wide gap and separate delivery of fuel and oxidizer

    Science.gov (United States)

    Frolov, S. M.; Dubrovskii, A. V.; Ivanov, V. S.

    2016-07-01

    The possibility of integrating the Continuous Detonation Chamber (CDC) in a gas turbine engine (GTE) is demonstrated by means of three-dimensional (3D) numerical simulations, i. e., the feasibility of the operation process in the annular combustion chamber with a wide gap and with separate feeding of fuel (hydrogen) and oxidizer (air) is proved computationally. The CDC with an upstream isolator damping pressure disturbances propagating towards the compressor is shown to exhibit a gain in the total pressure of 15% as compared with the same combustion chamber operating in the deflagration mode.

  12. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1987-01-01

    In-depth exploration of the implications of carrier populations and Fermi energies examines distribution of electrons in energy bands and impurity levels of semiconductors. Also: kinetics of semiconductors containing excess carriers, particularly in terms of trapping, excitation, and recombination.

  13. Polytypism in ZnS, ZnSe, and ZnTe: First-principles study

    KAUST Repository

    Boutaiba, F.

    2014-06-23

    We report results of first-principles calculations based on the projector augmented wave (PAW) method to explore the structural, thermodynamic, and electronic properties of cubic (3C) and hexagonal (6H, 4H, and 2H) polytypes of II-VI compounds: ZnS, ZnSe, and ZnTe. We find that the different bond stacking in II-VI polytypes remarkably influences the resulting physical properties. Furthermore, the degree of hexagonality is found to be useful to understand both the ground-state properties and the electronic structure of these compounds. The resulting lattice parameters, energetic stability, and characteristic band energies are in good agreement with available experimental data. Trends with hexagonality of the polytype are investigated.

  14. Phase transitions in ZnTe co-doped with Mg and oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Elyukhin, V.A.; Sorokina, L.P. [Departamento de Ingenieria Electrica, CINVESTAV-IPN, Av. IPN 2508, Mexico, D.F., 07360 (Mexico); Rodriguez de Santiago, M. [Departamento de Ingenieria Quimica Petrolera, IPN, Edif. 8, Mexico, D.F., 07738 (Mexico)

    2007-05-15

    Self-assembling of 1O4Mg tetrahedral clusters in ZnTe isoelectronically co-doped with Mg and oxygen in the ultra dilute oxygen impurity limit is described by a phase diagram. The occurrence of 1O4Mg clusters is a result of the second-order transition. The final stage of self-assembling when all oxygen impurities are in 1O4Mg clusters has to be reached also as a result of the second-order transition at the temperature close to the temperature of the occurrence of these clusters. The conditions of these phase transitions are obtained. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Structural and Optoelectrical Properties of ZnTe Thin Films Prepared by E-Beam Evaporation

    Science.gov (United States)

    Zia, Rehana; Saleemi, Farhat; Riaz, Madeeha; Nassem, Shahzad

    2016-10-01

    ZnTe thin films have been prepared by an electron-beam evaporation technique on glass substrates, changing the accelerating voltage and the substrate temperature at accelerating voltage of 2 kV. Structural analysis showed that all the films had cubic structure with preferential orientation along (111) direction, though (220) and (311) orientations were also present. The (111) peak intensity increased with increasing film thickness. The crystallite size increased with increasing film thickness. Conductivity measurements showed that the films were p-type. Films prepared at accelerating voltage of 2 kV exhibited minimum resistivity. Optical characterization indicated that both absorbing and transparent thin films can be achieved by using different deposition conditions. The optical bandgap value was found to vary with substrate temperature.

  16. Zinc-Based Semiconductors/Polymer Thin Films Junction for Photovoltaic Application

    Directory of Open Access Journals (Sweden)

    Souad Al-bat’hi

    2012-01-01

    Full Text Available Thin films of ZnO and ZnTe semiconductors were deposited on ITO conducting glass substrates by sputtering and electrodeposition techniques, respectively. On the other hand, thin films of ion conducting solid polymer electrolyte were prepared by solution cast technique. The polymer is a blend of 50 wt% polyethylene oxide and 50 wt% chitosan. To provide redox couple (I−/I3−, the polymer was complexed with ammonium iodide NH4I with addition of few crystals of iodine I2. Ammonium iodide NH4I was added to the solution in different amounts (wt% weight ratios to supply the charge carriers for the polymer electrolytes. The highest ionic conductivity of the polymer electrolyte was 1.18×10−5 S cm−1 at room temperature. Structural and optical properties of the semiconductor thin films were characterized by X-ray diffractometer and UV-Vis spectrophotometer. The XRD shows crystalline structures for both ZnO and ZnTe thin films. The UV-Vis shows direct energy gaps EZnO of 3.1 eV and EZnTe of 2.2 eV. The polymer film was sandwiched between the ZnO and ZnTe semiconductors to form ITO/ZnO/polymer/ZnTe/ITO double-junction photovoltaic cell, and the photovoltaic properties were studied. The highest open-circuit voltage oc, short-circuit current density sc, and fill factor FF of the fabricated cells are 0.5 V, 55 μA cm−2, and 27%, respectively.

  17. Semiconductor physics

    CERN Document Server

    Böer, Karl W

    2018-01-01

    This handbook gives a complete survey of the important topics and results in semiconductor physics. It addresses every fundamental principle and most research topics and areas of application in the field of semiconductor physics. Comprehensive information is provided on crystalline bulk and low-dimensional as well as amporphous semiconductors, including optical, transport, and dynamic properties.

  18. Zinc-Based Semiconductors/Polymer Thin Films Junction for Photovoltaic Application

    OpenAIRE

    Souad Al-bat’hi; Buhari, K. A.; Latiff, M. I.

    2012-01-01

    Thin films of ZnO and ZnTe semiconductors were deposited on ITO conducting glass substrates by sputtering and electrodeposition techniques, respectively. On the other hand, thin films of ion conducting solid polymer electrolyte were prepared by solution cast technique. The polymer is a blend of 50 wt% polyethylene oxide and 50 wt% chitosan. To provide redox couple (I−/I3−), the polymer was complexed with ammonium iodide NH4I with addition of few crystals of iodine I2. Ammonium iodide NH4I was...

  19. Effect of thickness on the microstructural, optoelectronic and morphological properties of electron beam evaporated ZnTe films

    Energy Technology Data Exchange (ETDEWEB)

    Balu, A.R.; Nagarethinam, V.S.; Thayumanavan, A. [Department of Physics, A.V.V.M Sri Pushpam College, Poondi, Thanjavur (India); Department of Physics, Alagappa University, Karaikudi 630003 (India); Murali, K.R.; Sanjeeviraja, C. [Electrochemical Materials Science Division, Central Electrochemical Research Institute, Karaikudi 630006 (India); Department of Physics, Alagappa University, Karaikudi 630003 (India); Jayachandran, M., E-mail: mjayam54@yahoo.co [Electrochemical Materials Science Division, Central Electrochemical Research Institute, Karaikudi 630006 (India); Department of Physics, Alagappa University, Karaikudi 630003 (India)

    2010-07-23

    ZnTe films of different thicknesses were deposited on glass substrates at a substrate temperature of 300 {sup o}C. The thickness of the films varied in the range of 110-320 nm. The films exhibited cubic structure with preferential orientation in the (1 1 1) direction. A very high value of absorption co-efficient (10{sup 4} cm{sup -1}) is observed. Band gap values in the range between 2.23 and 2.38 eV are observed when the film thickness was varied between 320 and 110 nm, respectively. The refractive index values are found to vary between 2.68 and 2.90 for the films of different thicknesses. It has been observed that the conductivity increases continuously with temperature as well as with thickness. Laser Raman spectra showed the presence of peaks at 206.8 and 411.2 cm{sup -1}corresponding to the first order and second order LO phonon of monophase ZnTe films. PL analysis confirmed the formation of monophase ZnTe films with nano grains.

  20. Optical properties and band alignments in ZnTe nanoparticles/MoS2 layer hetero-interface using SE and KPFM studies

    Science.gov (United States)

    Sharma, Intu; Mehta, B. R.

    2017-11-01

    Integration of a layered two-dimensional (2D) material with a non-2D material provides a platform where one can modulate and achieve the properties desired for various next-generation electronic and opto-electronic applications. Here, we investigated ZnTe nanoparticles/MoS2 hetero-interfaces with the thickness of the MoS2 varying from few to multilayer. High-resolution transmission electron microscopy was used to observe the crystalline behaviour of the ZnTe nanoparticles, while the number of MoS2 layers was investigated using Raman measurements. Spectroscopic ellipsometry (SE) analysis based on the five-layer fitting model was used to analyse the optical behaviour of the heterojunction, where the excitonic features corresponding to the MoS2 layers and absorption features due to the ZnTe nanoparticles are observed. From the Kelvin probe force microscopy (KPFM) measurements, the surface potential (SP) of the ZnTe nanoparticles/MoS2 is found to be different in comparison with the SP of the ZnTe nanoparticles and MoS2, which is indicative of the charge transfer at the ZnTe nanoparticles/MoS2 hetero-interface. Various parameters obtained using SE and KPFM measurements were used to propose energy band alignments at the ZnTe nanoparticles/MoS2 hetero-interface. In addition, an interface photovoltage of 193 mV was obtained by carrying out KPFM measurements under illuminating condition.

  1. Preparation and characterization of ZnTe as an interlayer for CdS/CdTe substrate thin film solar cells on flexible substrates

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xianjin, E-mail: xianjinfeng@gmail.com; Singh, Kartikay; Bhavanam, Sushma; Palekis, Vasilios; Morel, Don L.; Ferekides, Chris

    2013-05-01

    ZnTe thin films have been prepared on Mo-coated stainless steel substrates by the close spaced sublimation (CSS) technique. Cu-doped ZnTe (ZnTe:Cu) films are prepared by immersing the as-deposited samples in a CuCl–H{sub 2}O solution. The structural and morphological properties of the ZnTe films as a function of substrate temperature are investigated using X-ray diffraction and scanning electron microscopy. CdS/CdTe solar cells with and without the ZnTe and ZnTe:Cu interlayers are prepared and characterized with current–voltage (J–V), spectral response, and capacitance–voltage measurements. The structural and morphological properties of the ZnTe films prepared by CSS are found to be strongly influenced by the substrate temperature. The ‘roll-over’ behavior in the J–V characteristics of the CdS/CdTe solar cells due to a Schottky barrier at the back contact can be eliminated using ZnTe as the interlayer. Preliminary results on the application of ZnTe:Cu films suggest that the open circuit voltage and fill factor can be further improved, depending on processing conditions. - Highlights: ► Thin film CdTe solar cells on flexible stainless steel substrates are prepared. ► Using ZnTe can eliminate the ‘roll-over’ behavior in the current–voltage curve. ► Incorporating Cu can further improve the open circuit voltage and fill factor.

  2. Robust electronic and mechanical properties to layer number in 2D wide-gap X(OH)2 (X  =  Mg, Ca)

    Science.gov (United States)

    Xia, Congxin; Xiong, Wenqi; Du, Juan; Wang, Tianxing; Wei, Zhongming; Li, Jingbo

    2018-01-01

    Motivated by the recent synthesis of 2D alkaline-earth-metal hydroxide nanosheets, through first-principles calculations, we study the layer number and electric field modulations of the structural, electronic and mechanical properties of 2D X(OH)2 (X  =  Ca, Mg) multilayers. Increasing the layer number from one to ten, the Young’s modulus (Poisson’s ratio) slightly increases (decreases) and then remains saturated when the thickness is larger than four layers; while the characteristics of direct wide-gaps and work functions are robust to the layer number. In addition, the large elastic deformation (~20% biaxial stretch strain) indicates that 2D X(OH)2 possesses excellent mechanical flexibility. In particular, unlike conventional 2D materials, the electric field modulations of the band gap are very remarkable, especially for the X(OH)2 monolayer.

  3. A scaling rule of indentation hardness of semiconductors

    Science.gov (United States)

    Yonenaga, Ichiro; Suzuki, Takayoshi

    2003-03-01

    We report a scaling rule of the indentation hardness of semiconductor crystals from room temperature to their melting. The Vickers hardness of fifteen semiconductors, Si, Ge, SiC, AlN, GaN, GaP, GaAs, GaSb, InP, InAs, InSb, ZnO, ZnSe, ZnTe and CdTe, has been investigated from room temperature to their melting points. The temperature dependences of the hardness H v of eleven of these semiconductors, namely those with a cubic structure, obey a universal relationship when H v and the temperature T are scaled respectively by the shear modulus G and by G b ^3 / k _B, with b being the magnitude of the Burgers vector and k B the Boltzmann constant. The scaling rule is the same as that found for the temperature dependence of the critical shear stress τ c for the 111 slip system. The result leads a link between hardness and macroscopic yielding (dislocation motion). The relationshipH v = (70 ˜ 100) τ c is deduced for the cubic semiconductors is about ten times as large as the value for metals.

  4. Electronic stopping power of slow-light channeling ions in ZnTe from first principles

    Science.gov (United States)

    Li, Chang-kai; Mao, Fei; Wang, Feng; Fu, Yan-long; Ouyang, Xiao-ping; Zhang, Feng-Shou

    2017-05-01

    Nonadiabatic dynamics simulations are performed to investigate the electronic stopping power of a helium ion moving through ZnTe crystalline thin films under channeling conditions. Using ab initio time-dependent density-functional theory, we found by direct simulation that electronic stopping power versus projectile velocity deviates from velocity proportionality and displays a transition between two velocity regimes for helium ions channeling along middle crystalline axes in and channels and also in a channel with low-impact parameters. This transition causes a change in the slope of the energy loss versus ion velocity curve at a characteristic velocity related to the impact parameter and the lattice plane spacing. It may be an indication of extra energy loss channel beyond the electron-hole excitation. To analyze it, we checked the charge transfer between the moving projectiles and host atoms. It is found that the soft transition between two velocity regimes can be attributed to the resonant coherent excitation stimulated by the time-periodic potential experienced by the channeling ion and also the charge exchange in close encounters between Helium ion and host atoms.

  5. Semiconductor spintronics

    CERN Document Server

    Xia, Jianbai; Chang, Kai

    2012-01-01

    Semiconductor Spintronics, as an emerging research discipline and an important advanced field in physics, has developed quickly and obtained fruitful results in recent decades. This volume is the first monograph summarizing the physical foundation and the experimental results obtained in this field. With the culmination of the authors' extensive working experiences, this book presents the developing history of semiconductor spintronics, its basic concepts and theories, experimental results, and the prospected future development. This unique book intends to provide a systematic and modern foundation for semiconductor spintronics aimed at researchers, professors, post-doctorates, and graduate students, and to help them master the overall knowledge of spintronics.

  6. Macroporous Semiconductors

    Directory of Open Access Journals (Sweden)

    Helmut Föll

    2010-05-01

    Full Text Available Pores in single crystalline semiconductors come in many forms (e.g., pore sizes from 2 nm to > 10 µm; morphologies from perfect pore crystal to fractal and exhibit many unique properties directly or as nanocompounds if the pores are filled. The various kinds of pores obtained in semiconductors like Ge, Si, III-V, and II-VI compound semiconductors are systematically reviewed, emphasizing macropores. Essentials of pore formation mechanisms will be discussed, focusing on differences and some open questions but in particular on common properties. Possible applications of porous semiconductors, including for example high explosives, high efficiency electrodes for Li ion batteries, drug delivery systems, solar cells, thermoelectric elements and many novel electronic, optical or sensor devices, will be introduced and discussed.

  7. Temperature dependence of exciton peak energies in ZnS, ZnSe, and ZnTe epitaxial films

    Science.gov (United States)

    Pässler, R.; Griebl, E.; Riepl, H.; Lautner, G.; Bauer, S.; Preis, H.; Gebhardt, W.; Buda, B.; As, D. J.; Schikora, D.; Lischka, K.; Papagelis, K.; Ves, S.

    1999-10-01

    High-quality ZnS, ZnSe, and ZnTe epitaxial films were grown on (001)-GaAs-substrates by molecular beam epitaxy. The 1s-exciton peak energy positions have been determined by absorption measurements from 2 K up to about room temperature. For ZnS and ZnSe additional high-temperature 1s-exciton energy data were obtained by reflectance measurements performed from 300 up to about 550 K. These complete E1s(T) data sets are fitted using a recently developed analytical model. The high-temperature slopes of the individual E1s(T) curves and the effective phonon temperatures of ZnS, ZnSe, and ZnTe are found to scale almost linearly with the corresponding zero-temperature energy gaps and the Debye temperatures, respectively. Various ad hoc formulas of Varshni type, which have been invoked in recent articles for numerical simulations of restricted E1s(T) data sets for cubic ZnS, are discussed.

  8. Ab initio study of structural parameters and optical properties of ZnTe1-xOx

    Science.gov (United States)

    Zerroug, S.; Gueddim, A.; Ajmal Khan, M.; Bouarissa, N.

    2013-01-01

    The present work employs the full potential linearized augmented plane wave (FP-LAPW) technique to investigate the structural and optical properties of zinc-blende-structured ZnTe1-xOx with oxygen concentration in the range 0-1. Features such as lattice constant, bulk modulus and its pressure derivative have been reported. In agreement with X-ray diffraction measurement, it is found that the lattice constant of ZnTe1-xOx does not follow Vegard's law. In addition, the spectral dependence of the dielectric functions of the material system of interest for various oxygen concentrations at energies below and above the fundamental absorption edge are examined and discussed. The calculated static and high-frequency dielectric constants are found to agree reasonably well with those reported in the literature. Other case, our results are predictions. The information derived from the present study may be useful for optical emitters/converters or intermediate/defect band solar cells.

  9. Nucleation and formation of Au-catalyzed ZnTe nanowires on (0 0 1) GaAs by MBE: From planar to out-of-plane growth

    Science.gov (United States)

    Volobuev, V. V.; Groiss, H.; Halilovic, A.; Steiner, H.; Khiar, A.; Hesser, G.; Springholz, G.

    2017-11-01

    The growth evolution of gold-catalyzed ZnTe nanowire condensates on (0 0 1) GaAs substrates is studied. The samples are obtained by molecular beam epitaxy. The growth of nanowires has been monitored in situ by RHEED and investigated ex-situ by TEM, SEM, XRD. In addition to nanowires sticking out of surface in 〈 1 1 1 〉 direction, formation ZnTe thin film is observed. It is found, that formation of the nanowire condensate occurs in three stages. At the initial stage of growth planar nanowires form and continue to grow in 〈 1 1 0 〉 direction until their intersection occurs. After the intersection, nanowires change the growth direction from planar to out-of-plane. At the final stage of growth in-plane nanowires coalescence forming a thin film. In addition to main reflections from ZnTe nanowires some oriented spots and rings have been observed on RHEED patterns. We attribute these spots to twin formation in nanowires and rings to a presence of disoriented domains in ZnTe film condensates.

  10. Effect of Zn and Te beam intensity upon the film quality of ZnTe layers on severely lattice mismatched sapphire substrates by molecular beam epitaxy

    Science.gov (United States)

    Nakasu, Taizo; Sun, W.; Kobayashi, M.; Asahi, T.

    2017-06-01

    Zinc telluride layers were grown on highly-lattice-mismatched sapphire substrates by molecular beam epitaxy, and their crystallographic properties were studied by means of X-ray diffraction pole figures. The crystal quality of the ZnTe thin film was further studied by scanning electron microscopy, X-ray rocking curves and low-temperature photoluminescence measurements. These methods show that high-crystallinity (111)-oriented single domain ZnTe layers with the flat surface and good optical properties are realized when the beam intensity ratio of Zn and Te beams is adjusted. The migration of Zn and Te was inhibited by excess surface material and cracks were appeared. In particular, excess Te inhibited the formation of a high-crystallinity ZnTe film. The optical properties of the ZnTe layer revealed that the exciton-related features were dominant, and therefore the film quality was reasonably high even though the lattice constants and the crystal structures were severely mismatched.

  11. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1962-01-01

    Semiconductor Statistics presents statistics aimed at complementing existing books on the relationships between carrier densities and transport effects. The book is divided into two parts. Part I provides introductory material on the electron theory of solids, and then discusses carrier statistics for semiconductors in thermal equilibrium. Of course a solid cannot be in true thermodynamic equilibrium if any electrical current is passed; but when currents are reasonably small the distribution function is but little perturbed, and the carrier distribution for such a """"quasi-equilibrium"""" co

  12. Semiconductor electrochemistry

    CERN Document Server

    Memming, Rüdiger

    2015-01-01

    Providing both an introduction and an up-to-date survey of the entire field, this text captivates the reader with its clear style and inspiring, yet solid presentation. The significantly expanded second edition of this milestone work is supplemented by a completely new chapter on the hot topic of nanoparticles and includes the latest insights into the deposition of dye layers on semiconductor electrodes. In his monograph, the acknowledged expert Professor Memming primarily addresses physical and electrochemists, but materials scientists, physicists, and engineers dealing with semiconductor technology and its applications will also benefit greatly from the contents.

  13. Oxide semiconductors

    CERN Document Server

    Svensson, Bengt G; Jagadish, Chennupati

    2013-01-01

    Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. Originally widely known as the ""Willardson and Beer"" Series, it has succeeded in publishing numerous landmark volumes and chapters. The series publishes timely, highly relevant volumes intended for long-term impact and reflecting the truly interdisciplinary nature of the field. The volumes in Semiconductors and Semimetals have been and will continue to be of great interest to physicists, chemists, materials scientists, and device engineers in academia, scient

  14. Multicolor (UV-IR) Photodetectors Based on Lattice-Matched 6.1 A II/VI and III/V Semiconductors

    Science.gov (United States)

    2015-08-27

    infrared multi-color photodetector based on II-VI and III-V semiconductors. This photodetector consists of a newly-proposed CdTe /ZnTe/ CdTe nBn sub...perfectly conductive n- CdTe /p-InSb tunnel junction. 15. SUBJECT TERMS optical biasing; multi-junction photodetectors; triple-junction solar cell...Figure from Ref. [7].  Large-signal characteristics are measured with a single 780 nm laser diode at 100% modulation factor and 50% duty cycle [7

  15. Desorption of Te capping layer from ZnTe (100): Auger spectroscopy ...

    African Journals Online (AJOL)

    ... configurations of tellurium Te (c (2x2)) and Te (c (2x1)) are confirmed by scanning tunneling microscopy (STM). Such a study reveals a phase transition from a rich-Te to a poor-Te surface as the annealing temperature increases. Keywords: Zinc Tellure; solar cells; structural properties; optoelectronics; semiconductors.

  16. Ultrafast spectroscopy of semiconductors and semiconductor nanostructures

    CERN Document Server

    Shah, Jagdeep

    1996-01-01

    Ultrafast Spectroscopy of Semiconductors and Semiconductor Nanostructures Ultrafast spectroscopy of semiconductors is currently one of the most exciting areas of research in condensed-matter physics Remarkable recent progress in the generation of tunable femtosecond pulses has allowed direct investigation of the most fundamental dynamical processes in semiconductors This monograph presents some of the most striking recent advances in the field of ultrafast spectroscopy of semiconductors and their nanostructures After a brief overview of the basic concepts and of the recent advances in the techniques of ultrashort pulse generation and ultrafast spectroscopy, it discusses the physics of relaxation, tunneling and transport dynamics in semiconductors and semiconductor nanostructures following excitation by femtosecond laser pulses

  17. In situ characterization of ZnTe epilayer irradiation via time-resolved and power-density-dependent Raman spectroscopy

    Science.gov (United States)

    Wiedemeier, V.; Berth, G.; Zrenner, A.; Larramendi, E. M.; Woggon, U.; Lischka, K.; Schikora, D.

    2011-10-01

    Laser irradiation damage in ZnTe epilayers was analyzed in situ by power-density-dependent and time-resolved micro-Raman spectroscopy. Damage by ablation or compound decomposition on the sample surface was revealed by the decrease of the ZnTe-nLO mode intensity with the increase of laser power density. The appearance of the peaks associated with the stronger crystalline-tellurium modes, tellurium aggregates and second-order Raman scattering at room temperature μ-Raman spectra was observed for higher power densities than 4.4 × 105 W cm-2. The Raman signal time transients of ZnTe-nLO and crystalline-tellurium modes reveal an exponential evolution of the laser irradiation damage and a fast formation of crystalline tellurium aggregates on the layer surface.

  18. On the impact of isoelectric impurities on band bowing and disorder of compound semiconductors; Ueber den Einfluss von isoelektronischen Stoerstellen auf Bandbiegung und Unordnung in Verbindungshalbleitern

    Energy Technology Data Exchange (ETDEWEB)

    Karcher, Christian

    2012-03-16

    Isolectronic impurities and their impact on the properties of compound semiconductors is discussed in two systems: Nitrogen in Ga(As,P) quantum wells on the one hand and Sulfur and Selenium in bulk ZnTe. The properties are reduced to two experimentally observable aspects: Band Bowing, i.e. the non-linearity of the band gap of the compound semiconductor and disorder, i.e. in particular the formation of a strongly localized density of states beneath the fundamental band gap. Apart of the pure experimental studies an insight into the theoretical model of disorder-induced temperature dependent luminescence properties of the compound semiconductors by means of Monte Carlo Simulations is given.

  19. Coexistence of optically active radial and axial CdTe insertions in single ZnTe nanowire

    Science.gov (United States)

    Wojnar, P.; Płachta, J.; Zaleszczyk, W.; Kret, S.; Sanchez, Ana M.; Rudniewski, R.; Raczkowska, K.; Szymura, M.; Karczewski, G.; Baczewski, L. T.; Pietruczik, A.; Wojtowicz, T.; Kossut, J.

    2016-03-01

    We report on the growth, cathodoluminescence and micro-photoluminescence of individual radial and axial CdTe insertions in ZnTe nanowires. In particular, the cathodoluminescence technique is used to determine the position of each emitting object inside the nanowire. It is demonstrated that depending on the CdTe deposition temperature, one can obtain an emission either from axial CdTe insertions only, or from both, radial and axial heterostructures, simultaneously. At 350 °C CdTe grows only axially, whereas at 310 °C and 290 °C, there is also significant deposition on the nanowire sidewalls resulting in radial core/shell heterostructures. The presence of Cd atoms on the sidewalls is confirmed by energy dispersive X-ray spectroscopy. Micro-photoluminescence study reveals a strong linear polarization of the emission from both types of heterostructures in the direction along the nanowire axis.We report on the growth, cathodoluminescence and micro-photoluminescence of individual radial and axial CdTe insertions in ZnTe nanowires. In particular, the cathodoluminescence technique is used to determine the position of each emitting object inside the nanowire. It is demonstrated that depending on the CdTe deposition temperature, one can obtain an emission either from axial CdTe insertions only, or from both, radial and axial heterostructures, simultaneously. At 350 °C CdTe grows only axially, whereas at 310 °C and 290 °C, there is also significant deposition on the nanowire sidewalls resulting in radial core/shell heterostructures. The presence of Cd atoms on the sidewalls is confirmed by energy dispersive X-ray spectroscopy. Micro-photoluminescence study reveals a strong linear polarization of the emission from both types of heterostructures in the direction along the nanowire axis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08806b

  20. EDITORIAL: Oxide semiconductors

    Science.gov (United States)

    Kawasaki, M.; Makino, T.

    2005-04-01

    Blue or ultraviolet semiconducting light-emitting diodes have the potential to revolutionize illumination systems in the near-future. Such industrial need has propelled the investigation of several wide-gap semiconducting materials in recent years. Commercial applications include blue lasers for DVD memory and laser printers, while military applications are also expected. Most of the material development has so far been focused on GaN (band gap 3.5 eV at 2 K), and ZnSe (2.9 eV) because these two representative direct transition semiconductors are known to be bright emitting sources. GaN and GaN-based alloys are emerging as the winners in this field because ZnSe is subject to defect formation under high current drive. On the other hand, another II-VI compound, ZnO, has also excited substantial interest in the optoelectronics-oriented research communities because it is the brightest emitter of all, owing to the fact that its excitons have a 60 meV binding energy. This is compared with 26 meV for GaN and 20 meV for ZnSe. The stable excitons could lead to laser action based on their recombination even at temperatures well above room temperature. ZnO has additional major properties that are more advantageous than other wide-gap materials: availability of large area substrates, higher energy radiation stability, environmentally-friendly ingredients, and amenability to wet chemical etching. However, ZnO is not new to the semiconductor field as exemplified by several studies made during the 1960s on structural, vibrational, optical and electrical properties (Mollwo E 1982 Landolt-Boernstein New Series vol 17 (Berlin: Springer) p 35). In terms of devices, the luminescence from light-emitting diode structures was demonstrated in which Cu2O was used as the p-type material (Drapak I T 1968 Semiconductors 2 624). The main obstacle to the development of ZnO has been the lack of reproducible p-type ZnO. The possibility of achieving epitaxial p-type layers with the aid of thermal

  1. DESORPTION OF Te CAPPING LAYER FROM ZnTe (100: AUGER SPECTROSCOPY, LOW-ENERGY ELECTRON DIFFRACTION AND SCANNING TUNNELING MICROSCOPY

    Directory of Open Access Journals (Sweden)

    K. K. Sossoe

    2016-01-01

    Full Text Available The influence of the annealing temperature to desorb a protective Te capping layer of the zinc telluride (ZnTe (100 surface was investigated. The surface reconstruction of the ZnTe (100 upon the removal of a Te capping layer grown by the molecular beam epitaxy was characterized by different methods. Auger spectroscopy brought out the chemical composition of the surface before and after annealing; the Low-energy electron diffraction (LEED gave information about the crystallographic structure. The surface crystallographic configurations of tellurium Te (c (2x2 and Te (c (2x1 are confirmed by scanning tunneling microscopy (STM. Such a study reveals a phase transition from a rich-Te to a poor-Te surface as the annealing temperature increases. 

  2. Magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bihler, Christoph

    2009-04-15

    In this thesis we investigated in detail the properties of Ga{sub 1-x}Mn{sub x}As, Ga{sub 1-x}Mn{sub x}P, and Ga{sub 1-x}Mn{sub x}N dilute magnetic semiconductor thin films with a focus on the magnetic anisotropy and the changes of their properties upon hydrogenation. We applied two complementary spectroscopic techniques to address the position of H in magnetic semiconductors: (i) Electron paramagnetic resonance, which provides direct information on the symmetry of the crystal field of the Mn{sup 2+} atoms and (ii) x-ray absorption fine structure analysis which allows to probe the local crystallographic neighborhood of the absorbing Mn atom via analysing the fine structure at the Mn K absorption edge. Finally, we discussed the obstacles that have to be overcome to achieve Curie temperatures above the current maximum in Ga{sub 1-x}Mn{sub x}As of 185 K. Here, we outlined in detail the generic problem of the formation of precipitates at the example of Ge:MN. (orig.)

  3. Power semiconductors

    CERN Document Server

    Kubát, M

    1984-01-01

    The book contains a summary of our knowledge of power semiconductor structures. It presents first a short historic introduction (Chap. I) as well as a brief selection of facts from solid state physics, in particular those related to power semiconductors (Chap. 2). The book deals with diode structures in Chap. 3. In addition to fundamental facts in pn-junction theory, the book covers mainly the important processes of power structures. It describes the emitter efficiency and function of microleaks (shunts). the p +p and n + n junctions, and in particular the recent theory of the pin, pvn and p1tn junctions, whose role appears to be decisive for the forward mode not only of diode structures but also of more complex ones. For power diode structures the reverse mode is the decisive factor in pn-junction breakdown theory. The presentation given here uses engineering features (the multiplication factor M and the experimentally detected laws for the volume and surface of crystals), which condenses the presentation an...

  4. Semiconductor Laser Measurements Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Semiconductor Laser Measurements Laboratory is equipped to investigate and characterize the lasing properties of semiconductor diode lasers. Lasing features such...

  5. Growth of Wide Band Gap II-VI Compound Semiconductors by Physical Vapor Transport

    Science.gov (United States)

    Su, Ching-Hua; Sha, Yi-Gao

    1995-01-01

    The studies on the crystal growth and characterization of II-VI wide band gap compound semiconductors, such as ZnTe, CdS, ZnSe and ZnS, have been conducted over the past three decades. The research was not quite as extensive as that on Si, III-V, or even narrow band gap II-VI semiconductors because of the high melting temperatures as well as the specialized applications associated with these wide band gap semiconductors. In the past several years, major advances in the thin film technology such as Molecular Beam Epitaxy (MBE) and Metal Organic Chemical Vapor Deposition (MOCVD) have demonstrated the applications of these materials for the important devices such as light-emitting diode, laser and ultraviolet detectors and the tunability of energy band gap by employing ternary or even quaternary systems of these compounds. At the same time, the development in the crystal growth of bulk materials has not advanced far enough to provide low price, high quality substrates needed for the thin film growth technology.

  6. Fundamentals of semiconductor devices

    CERN Document Server

    Lindmayer, Joseph

    1965-01-01

    Semiconductor properties ; semiconductor junctions or diodes ; transistor fundamentals ; inhomogeneous impurity distributions, drift or graded-base transistors ; high-frequency properties of transistors ; band structure of semiconductors ; high current densities and mechanisms of carrier transport ; transistor transient response and recombination processes ; surfaces, field-effect transistors, and composite junctions ; additional semiconductor characteristics ; additional semiconductor devices and microcircuits ; more metal, insulator, and semiconductor combinations for devices ; four-pole parameters and configuration rotation ; four-poles of combined networks and devices ; equivalent circuits ; the error function and its properties ; Fermi-Dirac statistics ; useful physical constants.

  7. Structure and magnetism of transition-metal implanted dilute magnetic semiconductors

    CERN Document Server

    Pereira, Lino; Temst, K; Araújo, JP; Wahl, U

    The discovery of a dilute magnetic semiconductor (DMS) in which ferromagnetism is carrier-mediated and persists above room temperature is a critical step towards the development of semiconductor-based spintronics. Among the many types of DMS materials which have been investigated, the current research interest can be narrowed down to two main classes of materials: (1) narrow-gap III-V semiconductors, mostly GaAs and InAs, doped with Mn; (2) wide-gap oxides and nitrides doped with 3d transition metals, mostly Mn- and Co-doped ZnO and Mn-doped GaN. With a number of interesting functionalities deriving from the carrier-mediated ferromagnetism and demonstrated in various proof-of-concept devices, Mn-doped GaAs has become, among DMS materials, one of the best candidates for technological application. However, despite major developments over the last 15 years, the maximum Curie temperature (185 K) remains well below room temperature. On the other hand, wide-gap DMS materials appear to exhibit ferromagnetic behavior...

  8. Reserve current analysis in semiconductor insulator semiconductor ...

    African Journals Online (AJOL)

    Reserve current analysis in semiconductor insulator semiconductor (SIS) solar cells. H Yakubu, PK Mensah. Abstract. No Abstract. Journal of the Ghana Association Vol. 2 (3) 1999: pp. 1-4. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.

  9. Optimization of the p+-ZnTe layer for back contacts of ZnTe thin-film solar cells

    Science.gov (United States)

    Lee, Kyoung Su; Oh, Gyujin; Kim, Eun Kyu

    2016-08-01

    We have studied the performance of ZnTe-based heterojunction diodes grown on p-GaAs substrates by using pulsed laser deposition (PLD). In the X-ray diffraction measurements, ZnTe and CdS thin films grown on p-GaAs (100) substrates appeared to have a cubic crystalline structure while the ZnO film showed a hexagonal structure. The structure of n+-ZnO/i-ZnTe/p-GaAs with insertion of a CdS buffer layer between n+-ZnO and i-ZnTe showed strong rectifying diode characteristics, and its open-circuit voltage (V oc ) and short-circuit current density (J sc ) under 1,000 Wm-2 air mass 1.5 global (AM 1.5G) illumination were measured about 0.32 V and 0.61 mAcm-2, respectively. When an inserted another layer, a ZnTe:Cu layer, as a p+-layer for the contacts on p-GaAs substrate, the value of V oc and J sc of the n+-ZnO/CdS/i-ZnTe/ZnTe:Cu/p-GaAs structure increased to 0.39 V and 0.81 mA/cm2, respectively. As the thickness of i-ZnTe were increased from 210 to 420 nm, the photoelectric conversion efficiency of the n+-ZnO/CdS/i-ZnTe/ZnTe:Cu/p-GaAs structure increased to 0.24%.

  10. Handbook of spintronic semiconductors

    CERN Document Server

    Chen, Weimin

    2010-01-01

    Offers a review of the field of spintronic semiconductors. This book covers a range of topics, including growth and basic physical properties of diluted magnetic semiconductors based on II-VI, III-V and IV semiconductors, developments in theory and experimental techniques and potential device applications.

  11. Effect of growth temperature, thermal annealing and nitrogen doping on optoelectronic properties of sputter-deposited ZnTe films

    Energy Technology Data Exchange (ETDEWEB)

    Rakhshani, A.E., E-mail: ali.rakhshani@ku.edu.kw

    2013-06-01

    Thin films of zinc telluride were grown on glass substrate at different temperatures by magnetron sputtering. Nitrogen-doped films were also prepared at different doping levels. Films underwent a post deposition thermal annealing at low pressure of nitrogen. The film structure, optical and electrical properties were studied using various techniques. The results revealed that the films are composed from nano-size grains (3 – 19 nm) with cubic lattice structure. The grain growth during deposition is thermally activated with the activation energy of 108 meV. Direct optical transitions occurring from the valence band and also from the spin-orbit valence band to either a band gap defect level (for as-grown films) or to the conduction band (for annealed films) have been observed. The valence band split energy is found to be in the range 0.82 – 1.10 eV. The defect level, likely related to oxygen impurities, is located 1.77 eV above the valence band edge. The band gap energy of the annealed films is in the range 2.13 – 2.20 eV and the films doped with nitrogen, at optimum condition, have a free hole concentration and mobility of 2.9 × 10{sup 18} cm{sup −3} and 1.4 cm{sup 2} V{sup −1} s{sup −1}, respectively. - Highlights: • Undoped and nitrogen doped ZnTe films were grown on glass by sputtering technique. • Growth temperature varied in the range 35– 305 °C. • Optimum doping was achieved at the N{sub 2}/(N{sub 2} + Ar) flow rate ratio of 2%. • At optimum condition 2.9 × 10{sup 18} holes/cm{sup 3} with mobility 1.4 cm{sup 2} V{sup −1} s{sup −1} were obtained. • The split valence band and oxygen defects contribute to the absorption of light.

  12. Donor impurity incorporation during layer growth of Zn II-VI semiconductors

    Science.gov (United States)

    Barlow, D. A.

    2017-12-01

    The maximum halogen donor concentration in Zn II-VI semiconductors during layer growth is studied using a standard model from statistical mechanics. Here the driving force for incorporation is an increase in entropy upon mixing of the donor impurity into the available anion lattice sites in the host binary. A formation energy opposes this increase and thus equilibrium is attained at some maximum concentration. Considering the halogen donor impurities within the Zn II-VI binary semiconductors ZnO, ZnS, ZnSe and ZnTe, a heat of reaction obtained from reported diatomic bond strengths is shown to be directly proportional to the log of maximum donor concentration. The formation energy can then be estimated and an expression for maximum donor concentration derived. Values for the maximum donor concentration with each of the halogen impurities, within the Zn II-VI compounds, are computed. This model predicts that the halogens will serve as electron donors in these compounds in order of increasing effectiveness as: F, Br, I, Cl. Finally, this result is taken to be equivalent to an alternative model where donor concentration depends upon impurity diffusion and the conduction band energy shift due to a depletion region at the growing crystal's surface. From this, we are able to estimate the diffusion activation energy for each of the impurities mentioned above. Comparisons are made with reported values and relevant conclusions presented.

  13. Semiconductor Physical Electronics

    CERN Document Server

    Li, Sheng

    2006-01-01

    Semiconductor Physical Electronics, Second Edition, provides comprehensive coverage of fundamental semiconductor physics that is essential to an understanding of the physical and operational principles of a wide variety of semiconductor electronic and optoelectronic devices. This text presents a unified and balanced treatment of the physics, characterization, and applications of semiconductor materials and devices for physicists and material scientists who need further exposure to semiconductor and photonic devices, and for device engineers who need additional background on the underlying physical principles. This updated and revised second edition reflects advances in semicondutor technologies over the past decade, including many new semiconductor devices that have emerged and entered into the marketplace. It is suitable for graduate students in electrical engineering, materials science, physics, and chemical engineering, and as a general reference for processing and device engineers working in the semicondi...

  14. Semiconductor devices physics and technology

    CERN Document Server

    Sze, Simon

    2012-01-01

    Semiconductor Devices: Physics and Technology, Third Edition is an introduction to the physical principles of modern semiconductor devices and their advanced fabrication technology. It begins with a brief historical review of major devices and key technologies and is then divided into three sections: semiconductor material properties, physics of semiconductor devices and processing technology to fabricate these semiconductor devices.

  15. Semiconductor Electrical Measurements Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Semiconductor Electrical Measurements Laboratory is a research laboratory which complements the Optical Measurements Laboratory. The laboratory provides for Hall...

  16. Basic semiconductor physics

    CERN Document Server

    Hamaguchi, Chihiro

    2001-01-01

    This book presents a detailed description of the basic physics of semiconductors. All the important equations describing the properties of these materials are derived without the help of other textbooks. The reader is assumed to have only a basic command of mathematics and some elementary semiconductor physics. The text covers a wide range of important semiconductor phenomena, from the simple to the advanced. Examples include recent progress in semiconductor quantum structures such as two-dimensional electron-gas systems, ballistic transport, the quantum Hall effect, the Landauer formula, the Coulomb blockade and the single-electron transistor.

  17. Semiconductor radiation detectors. Device physics

    Energy Technology Data Exchange (ETDEWEB)

    Lutz, G. [Max-Planck-Institut fuer Physik, Muenchen (Germany)]|[Max-Planck-Institut fuer Extraterrestrische Physik, Garching (Germany). Semiconductor Lab.

    1999-07-01

    The following topics were dealt with: semiconductor radiation detectors, basic semiconductor structures, semiconductors, energy measurement, radiation-level measurement, position measurement, electronics of the readout function, detectors with intrinsic amplification, detector technology, device stability, radiation hardness and device simulation.

  18. Electron Band Alignment at Interfaces of Semiconductors with Insulating Oxides: An Internal Photoemission Study

    Directory of Open Access Journals (Sweden)

    Valeri V. Afanas'ev

    2014-01-01

    Full Text Available Evolution of the electron energy band alignment at interfaces between different semiconductors and wide-gap oxide insulators is examined using the internal photoemission spectroscopy, which is based on observations of optically-induced electron (or hole transitions across the semiconductor/insulator barrier. Interfaces of various semiconductors ranging from the conventional silicon to the high-mobility Ge-based (Ge, Si1-xGex, Ge1-xSnx and AIIIBV group (GaAs, InxGa1-xAs, InAs, GaP, InP, GaSb, InSb materials were studied revealing several general trends in the evolution of band offsets. It is found that in the oxides of metals with cation radii larger than ≈0.7 Å, the oxide valence band top remains nearly at the same energy (±0.2 eV irrespective of the cation sort. Using this result, it becomes possible to predict the interface band alignment between oxides and semiconductors as well as between dissimilar insulating oxides on the basis of the oxide bandgap width which are also affected by crystallization. By contrast, oxides of light elements, for example, Be, Mg, Al, Si, and Sc exhibit significant shifts of the valence band top. General trends in band lineup variations caused by a change in the composition of semiconductor photoemission material are also revealed.

  19. Deep level transient spectroscopy of hole traps related to CdTe self-assembled quantum dots embedded in ZnTe matrix.

    Science.gov (United States)

    Zielony, E; Placzek-Popko, E; Dyba, P; Gumienny, Z; Szatkowski, J; Dobaczewski, L; Karczewski, G

    2011-08-01

    The capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements have been made on a Schottky Ti-ZnTe (p-type) diode containing CdTe self-assembled quantum dots (QD) and control diode without dots. The C-V curve of the QD diode exhibits a characteristic step associated with the QD states whereas the reference diode shows ordinary bulk behavior. A quasistatic model based on the self-consistent solution of the Poisson's equation is used to simulate the capacitance. By comparison of the calculated C-V curve with the experimental one, hole binding energy at the QD states is found to be equal about 0.12 eV. The results of DLTS measurements for the sample containing QDs reveal the presence of a low-temperature peak which is not observed for the control diode. Analysis of its behavior at different bias conditions leads to the conclusion that this peak may be related to the hole emission from the QD states to the ZnTe valence band. Its thermal activation energy obtained from related Arrhenius plot equals to 0.12 eV in accordance with the energy obtained from the Poisson's equation. Thus based on the C-V and DLTS studies it may be concluded that the thermal activation energy of holes from the QD states to the ZnTe valence band in the CdTe/ZnTe QD system is equal about 0.12 eV.

  20. Semiconductors data handbook

    CERN Document Server

    Madelung, Otfried

    2004-01-01

    This volume Semiconductors: Data Handbook contains frequently used data from the corresponding larger Landolt-Börnstein handbooks in a low price book for the individual scientist working in the laboratory. The Handbook contain important information about a large number of semiconductors

  1. High energy semiconductor switch

    Science.gov (United States)

    Risberg, R. L.

    1989-02-01

    The objective was a controller for electric motors. By operating standard Nema B induction motors at variable speed a great deal of energy is saved. This is especially true in pumping and air conditioning applications. To allow wider use of variable speed AC drives, and to provide improved performance, a better semiconductor switch was sought. This was termed the High Energy Semiconductor Switch.

  2. Semiconductor radiation detection systems

    CERN Document Server

    2010-01-01

    Covers research in semiconductor detector and integrated circuit design in the context of medical imaging using ionizing radiation. This book explores other applications of semiconductor radiation detection systems in security applications such as luggage scanning, dirty bomb detection and border control.

  3. Semiconductor Research Experimental Techniques

    CERN Document Server

    Balkan, Naci

    2012-01-01

    The book describes the fundamentals, latest developments and use of key experimental techniques for semiconductor research. It explains the application potential of various analytical methods and discusses the opportunities to apply particular analytical techniques to study novel semiconductor compounds, such as dilute nitride alloys. The emphasis is on the technique rather than on the particular system studied.

  4. Spin physics in semiconductors

    CERN Document Server

    Dyakonov, Mikhail I

    2008-01-01

    This book describes beautiful optical and transport phenomena related to the electron and nuclear spins in semiconductors with emphasis on a clear presentation of the physics involved. Recent results on quantum wells and quantum dots are reviewed. The book is intended for students and researchers in the fields of semiconductor physics and nanoelectronics.

  5. Simulations of defect spin qubits in piezoelectric semiconductors

    Science.gov (United States)

    Seo, Hosung

    In recent years, remarkable advances have been reported in the development of defect spin qubits in semiconductors for solid-state quantum information science and quantum metrology. Promising spin qubits include the nitrogen-vacancy center in diamond, dopants in silicon, and the silicon vacancy and divacancy spins in silicon carbide. In this talk, I will highlight some of our recent efforts devoted to defect spin qubits in piezoelectric wide-gap semiconductors for potential applications in mechanical hybrid quantum systems. In particular, I will describe our recent combined theoretical and experimental study on remarkably robust quantum coherence found in the divancancy qubits in silicon carbide. We used a quantum bath model combined with a cluster expansion method to identify the microscopic mechanisms behind the unusually long coherence times of the divacancy spins in SiC. Our study indicates that developing spin qubits in complex crystals with multiple types of atom is a promising route to realize strongly coherent hybrid quantum systems. I will also discuss progress and challenges in computational design of new spin defects for use as qubits in piezoelectric crystals such as AlN and SiC, including a new defect design concept using large metal ion - vacancy complexes. Our first principles calculations include DFT computations using recently developed self-consistent hybrid density functional theory and large-scale many-body GW theory. This work was supported by the National Science Foundation (NSF) through the University of Chicago MRSEC under Award Number DMR-1420709.

  6. Physics of semiconductor lasers

    CERN Document Server

    Mroziewicz, B; Nakwaski, W

    2013-01-01

    Written for readers who have some background in solid state physics but do not necessarily possess any knowledge of semiconductor lasers, this book provides a comprehensive and concise account of fundamental semiconductor laser physics, technology and properties. The principles of operation of these lasers are therefore discussed in detail with the interrelations between their design and optical, electrical and thermal properties. The relative merits of a large number of laser structures and their parameters are described to acquaint the reader with the various aspects of the semiconductor l

  7. Defects in semiconductors

    CERN Document Server

    Romano, Lucia; Jagadish, Chennupati

    2015-01-01

    This volume, number 91 in the Semiconductor and Semimetals series, focuses on defects in semiconductors. Defects in semiconductors help to explain several phenomena, from diffusion to getter, and to draw theories on materials' behavior in response to electrical or mechanical fields. The volume includes chapters focusing specifically on electron and proton irradiation of silicon, point defects in zinc oxide and gallium nitride, ion implantation defects and shallow junctions in silicon and germanium, and much more. It will help support students and scientists in their experimental and theoret

  8. Semiconductors bonds and bands

    CERN Document Server

    Ferry, David K

    2013-01-01

    As we settle into this second decade of the twenty-first century, it is evident that the advances in micro-electronics have truly revolutionized our day-to-day lifestyle. The technology is built upon semiconductors, materials in which the band gap has been engineered for special values suitable to the particular application. This book, written specifically for a one semester course for graduate students, provides a thorough understanding of the key solid state physics of semiconductors. It describes how quantum mechanics gives semiconductors unique properties that enabled the micro-electronics revolution, and sustain the ever-growing importance of this revolution.

  9. Spin physics in semiconductors

    CERN Document Server

    2017-01-01

    This book offers an extensive introduction to the extremely rich and intriguing field of spin-related phenomena in semiconductors. In this second edition, all chapters have been updated to include the latest experimental and theoretical research. Furthermore, it covers the entire field: bulk semiconductors, two-dimensional semiconductor structures, quantum dots, optical and electric effects, spin-related effects, electron-nuclei spin interactions, Spin Hall effect, spin torques, etc. Thanks to its self-contained style, the book is ideally suited for graduate students and researchers new to the field.

  10. Compact semiconductor lasers

    CERN Document Server

    Yu, Siyuan; Lourtioz, Jean-Michel

    2014-01-01

    This book brings together in a single volume a unique contribution by the top experts around the world in the field of compact semiconductor lasers to provide a comprehensive description and analysis of the current status as well as future directions in the field of micro- and nano-scale semiconductor lasers. It is organized according to the various forms of micro- or nano-laser cavity configurations with each chapter discussing key technical issues, including semiconductor carrier recombination processes and optical gain dynamics, photonic confinement behavior and output coupling mechanisms, carrier transport considerations relevant to the injection process, and emission mode control. Required reading for those working in and researching the area of semiconductors lasers and micro-electronics.

  11. Defects in semiconductor nanostructures

    Science.gov (United States)

    Singh, Vijay A.; Harbola, Manoj K.; Pathak, Praveen

    2008-02-01

    Impurities play a pivotal role in semiconductors. One part in a million of phosphorous in silicon alters the conductivity of the latter by several orders of magnitude. Indeed, the information age is possible only because of the unique role of shallow impurities in semiconductors. Although work in semiconductor nanostructures (SN) has been in progress for the past two decades, the role of impurities in them has been only sketchily studied. We outline theoretical approaches to the electronic structure of shallow impurities in SN and discuss their limitations. We find that shallow levels undergo a SHADES (SHAllow-DEep-Shallow) transition as the SN size is decreased. This occurs because of the combined effect of quantum confinement and reduced dielectric constant in SN. Level splitting is pronounced and this can perhaps be probed by ESR and ENDOR techniques. Finally, we suggest that a perusal of literature on (semiconductor) cluster calculations carried out 30 years ago would be useful.

  12. Physics of semiconductor devices

    CERN Document Server

    Rudan, Massimo

    2015-01-01

    This book describes the basic physics of semiconductors, including the hierarchy of transport models, and connects the theory with the functioning of actual semiconductor devices.  Details are worked out carefully and derived from the basic physics, while keeping the internal coherence of the concepts and explaining various levels of approximation. Examples are based on silicon due to its industrial importance. Several chapters are included that provide the reader with the quantum-mechanical concepts necessary for understanding the transport properties of crystals. The behavior of crystals incorporating a position-dependent impurity distribution is described, and the different hierarchical transport models for semiconductor devices are derived (from the Boltzmann transport equation to the hydrodynamic and drift-diffusion models). The transport models are then applied to a detailed description of the main semiconductor-device architectures (bipolar, MOS). The final chapters are devoted to the description of s...

  13. Biggest semiconductor installed

    CERN Multimedia

    2008-01-01

    Scientists and technicians at the European Laboratory for Particle Physics, commonly known by its French acronym CERN (Centre Europen pour la Recherche Nuclaire), have completed the installation of the largest semiconductor silicon detector.

  14. Electrowetting on a semiconductor

    OpenAIRE

    Arscott, Steve; Gaudet, Matthieu

    2012-01-01

    We report electrowetting on a semiconductor using of a mercury droplet resting on a silicon surface. The effect is demonstrated using commercial n-type and p-type single-crystal (100) silicon wafers of different doping levels. The electrowetting is reversible - the voltage-dependent wetting contact angle variation of the mercury droplet is observed to depend on both the underlying semiconductor doping density and type. The electrowetting behaviour is explained by the voltage-dependent modulat...

  15. Radiation effects in semiconductors

    CERN Document Server

    2011-01-01

    There is a need to understand and combat potential radiation damage problems in semiconductor devices and circuits. Written by international experts, this book explains the effects of radiation on semiconductor devices, radiation detectors, and electronic devices and components. These contributors explore emerging applications, detector technologies, circuit design techniques, new materials, and innovative system approaches. The text focuses on how the technology is being used rather than the mathematical foundations behind it. It covers CMOS radiation-tolerant circuit implementations, CMOS pr

  16. Hydrogen in semiconductors II

    CERN Document Server

    Nickel, Norbert H; Weber, Eicke R; Nickel, Norbert H

    1999-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The "Willardson and Beer" Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices, Oxygen in Silicon, and others promise that this tradition ...

  17. Basic Semiconductor Physics

    CERN Document Server

    Hamaguchi, Chihiro

    2010-01-01

    This book presents a detailed description of the basic semiconductor physics. The reader is assumed to have a basic command of mathematics and some elementary knowledge of solid state physics. The text covers a wide range of important phenomena in semiconductors, from the simple to the advanced. The reader can understand three different methods of energy band calculations, empirical pseudo-potential, k.p perturbation and tight-binding methods. The effective mass approximation and electron motion in a periodic potential, Boltzmann transport equation and deformation potentials used for full band Monte Carlo simulation are discussed. Experiments and theoretical analysis of cyclotron resonance are discussed in detail because the results are essential to the understanding of semiconductor physics. Optical and transport properties, magneto-transport, two dimensional electron gas transport (HEMT and MOSFET), and quantum transport are reviewed, explaining optical transition, electron phonon interactions, electron mob...

  18. Compound semiconductor device physics

    CERN Document Server

    Tiwari, Sandip

    2013-01-01

    This book provides one of the most rigorous treatments of compound semiconductor device physics yet published. A complete understanding of modern devices requires a working knowledge of low-dimensional physics, the use of statistical methods, and the use of one-, two-, and three-dimensional analytical and numerical analysis techniques. With its systematic and detailed**discussion of these topics, this book is ideal for both the researcher and the student. Although the emphasis of this text is on compound semiconductor devices, many of the principles discussed will also be useful to those inter

  19. Semiconductor opto-electronics

    CERN Document Server

    Moss, TS; Ellis, B

    1972-01-01

    Semiconductor Opto-Electronics focuses on opto-electronics, covering the basic physical phenomena and device behavior that arise from the interaction between electromagnetic radiation and electrons in a solid. The first nine chapters of this book are devoted to theoretical topics, discussing the interaction of electromagnetic waves with solids, dispersion theory and absorption processes, magneto-optical effects, and non-linear phenomena. Theories of photo-effects and photo-detectors are treated in detail, including the theories of radiation generation and the behavior of semiconductor lasers a

  20. Introductory semiconductor device physics

    CERN Document Server

    Parker, Greg

    2004-01-01

    ATOMS AND BONDINGThe Periodic TableIonic BondingCovalent BondingMetallic bondingvan der Waals BondingStart a DatabaseENERGY BANDS AND EFFECTIVE MASSSemiconductors, Insulators and MetalsSemiconductorsInsulatorsMetalsThe Concept of Effective MassCARRIER CONCENTRATIONS IN SEMICONDUCTORSDonors and AcceptorsFermi-LevelCarrier Concentration EquationsDonors and Acceptors Both PresentCONDUCTION IN SEMICONDUCTORSCarrier DriftCarrier MobilitySaturated Drift VelocityMobility Variation with TemperatureA Derivation of Ohm's LawDrift Current EquationsSemiconductor Band Diagrams with an Electric Field Presen

  1. Ternary chalcopyrite semiconductors

    CERN Document Server

    Shay, J L; Pamplin, B R

    2013-01-01

    Ternary Chalcopyrite Semiconductors: Growth, Electronic Properties, and Applications covers the developments of work in the I-III-VI2 and II-IV-V2 ternary chalcopyrite compounds. This book is composed of eight chapters that focus on the crystal growth, characterization, and applications of these compounds to optical communications systems. After briefly dealing with the status of ternary chalcopyrite compounds, this book goes on describing the crystal growth of II-IV-V2 and I-III-VI2 single crystals. Chapters 3 and 4 examine the energy band structure of these semiconductor compounds, illustrat

  2. Optical processes in semiconductors

    CERN Document Server

    Pankove, Jacques I

    1975-01-01

    Based on a series of lectures at Berkeley, 1968-1969, this is the first book to deal comprehensively with all of the phenomena involving light in semiconductors. The author has combined, for the graduate student and researcher, a great variety of source material, journal research, and many years of experimental research, adding new insights published for the first time in this book.Coverage includes energy states in semiconductors and their perturbation by external parameters, absorption, relationships between optical constants, spectroscopy, radiative transitions, nonradiative recombination

  3. Growth of photovoltaic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yablonovitch, E. (Bell Communications Research, Red Bank, NJ (United States)); Stringfellow, G.B. (Univ. of Utah, Salt Lake City (United States)); Greene, J.E. (Univ. of Illinois, Urbana (United States))

    1993-01-01

    We assess the opportunities for improving the quality and lowering the cost of thin crystalline semiconductor films for photovoltaics. We find that novel growth and processing methods can lower the cost of crystalline semiconductor films to satisfy the economic conditions for a major expansion of the photovoltaic industry. The research requirements are in the areas of novel precursors for vapor phase growth, atomic layer epitaxy for unprecedented control, and the requirement for novel in situ and ex situ probes to ensure that the new growth methods are producing the utmost in photovoltaic material quality. 42 refs.

  4. Advances in semiconductor lasers

    CERN Document Server

    Coleman, James J; Jagadish, Chennupati

    2012-01-01

    Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. Originally widely known as the ""Willardson and Beer"" Series, it has succeeded in publishing numerous landmark volumes and chapters. The series publishes timely, highly relevant volumes intended for long-term impact and reflecting the truly interdisciplinary nature of the field. The volumes in Semiconductors and Semimetals have been and will continue to be of great interest to physicists, chemists, materials scientists, and device engineers in academia, scien

  5. Molecular Dynamics Study of Poly And Monocrystalline CdS/CdTe Junctions and Cu Doped Znte Back Contacts for Solar Cell Applications

    Science.gov (United States)

    Aguirre, Rodolfo, II

    Cadmium telluride (CdTe) is a material used to make solar cells because it absorbs the sunlight very efficiently and converts it into electricity. However, CdTe modules suffer from degradation of 1% over a period of 1 year. Improvements on the efficiency and stability can be achieved by designing better materials at the atomic scale. Experimental techniques to study materials at the atomic scale, such as Atomic Probe Tomography (APT) and Transmission Electron Microscope (TEM) are expensive and time consuming. On the other hand, Molecular Dynamics (MD) offers an inexpensive and fast computer simulation technique to study the growth evolution of materials with atomic scale resolution. In combination with advance characterization software, MD simulations provide atomistic visualization, defect analysis, structure maps, 3-D atomistic view, and composition profiles. MD simulations help to design better quality materials by predicting material behavior at the atomic scale. In this work, a new MD method to study several phenomena such as polycrystalline growth of CdTe-based materials, interdiffusion of atoms at interfaces, and deposition of a copper doped ZnTe back contact is established. Results are compared with experimental data found in the literature and experiments performed and shown to be in remarkably good agreement.

  6. Metal semiconductor contacts and devices

    CERN Document Server

    Cohen, Simon S; Einspruch, Norman G

    1986-01-01

    VLSI Electronics Microstructure Science, Volume 13: Metal-Semiconductor Contacts and Devices presents the physics, technology, and applications of metal-semiconductor barriers in digital integrated circuits. The emphasis is placed on the interplay among the theory, processing, and characterization techniques in the development of practical metal-semiconductor contacts and devices.This volume contains chapters that are devoted to the discussion of the physics of metal-semiconductor interfaces and its basic phenomena; fabrication procedures; and interface characterization techniques, particularl

  7. Handbook of luminescent semiconductor materials

    CERN Document Server

    Bergman, Leah

    2011-01-01

    Photoluminescence spectroscopy is an important approach for examining the optical interactions in semiconductors and optical devices with the goal of gaining insight into material properties. With contributions from researchers at the forefront of this field, Handbook of Luminescent Semiconductor Materials explores the use of this technique to study semiconductor materials in a variety of applications, including solid-state lighting, solar energy conversion, optical devices, and biological imaging. After introducing basic semiconductor theory and photoluminescence principles, the book focuses

  8. Scanning Tunneling Microscopy of 3-5 Semiconductors

    Science.gov (United States)

    1993-01-29

    thai the slab may be too thin . TABU HI. Calculated difference* in «ionic dJaplacemeau Alt (in A) ZnTe (ttO) surface for a su4aycr model min*» a tve...and 0. F. Sankey. Relaxation of the ZnTe and CuCi’(uS)’surf aces J. Vac. Sei. Technol. A 10, 2511-2514 (1992). (MS 275) M.-H. Tsai, C S. Chang, J...monocrystal- line films were grown on the Si-terminated (0001) surface of hexagonal a-SiC substrates hy the technique of chemi- cal vapor deposition

  9. Enhanced electrical transparency by ultra-thin LaAlO3 insertion at oxide metal/semiconductor heterointerfaces

    Energy Technology Data Exchange (ETDEWEB)

    Yajima, Takeaki [SLAC National Accelerator Lab., Menlo Park, CA (United States); The Univ. of Tokyo, Tokyo (Japan); Minohara, Makoto [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Bell, Christopher [SLAC National Accelerator Lab., Menlo Park, CA (United States); ; Kumigashira, Hiroshi [Stanford Univ., Stanford, CA (United States); Oshima, Masaharu [The Univ. of Tokyo, Tokyo (Japan); Hwang, Harold Y. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Hikita, Yasuyuki [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-02-05

    We demonstrate that the electrical conductivity of metal/semiconductor oxide heterojunctions can be increased over 7 orders of magnitude by inserting an ultrathin layer of LaAlO3. This counterintuitive result, that an interfacial barrier can be driven transparent by inserting a wide-gap insulator, arises from the large internal electric field between the two polar LaAlO3 surfaces. In conclusion, this field modifies the effective band offset in the device, highlighting the ability to design the electrostatic boundary conditions with atomic precision.

  10. Terahertz semiconductor nonlinear optics

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias

    2013-01-01

    In this proceedings we describe our recent results on semiconductor nonlinear optics, investigated using single-cycle THz pulses. We demonstrate the nonlinear absorption and self-phase modulation of strong-field THz pulses in doped semiconductors, using n-GaAs as a model system. The THz nonlinear......In this proceedings we describe our recent results on semiconductor nonlinear optics, investigated using single-cycle THz pulses. We demonstrate the nonlinear absorption and self-phase modulation of strong-field THz pulses in doped semiconductors, using n-GaAs as a model system. The THz...... is determined by (but not equal to) the electron momentum relaxation rate. Single cycle pulses of light, irrespective of the frequency range to which they belong, inherently have an ultrabroadband spectrum covering many octaves of frequencies. Unlike the single-cycle pulses in optical domain, the THz pulses can...... be easily sampled with sub-cycle resolution using conventional femtosecond lasers. This makes the THz pulses accessible model tools for direct observation of general nonlinear optical phenomena occurring in the single-cycle regime....

  11. Physics of semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    Prew, B.A.

    1975-09-01

    The properties of semiconductors which make them important in the electronic devices industry, and how these properties are controlled by doping, are described. The physics and applications of p-n and other junction devices, and of bulk effect devices are discussed. Avalanche devices, optical devices, solar cells, Schottky barriers, MOS devices, heterojunctions, photoconductors, and transferred electron devices are considered.

  12. Defects in semiconductor nanostructures

    Indian Academy of Sciences (India)

    11] A detailed review article of defects in semiconductor nanostructures is currently under preparation. [12] V Ranjan and Vijay A Singh, J. Appl. Phys. 89, 6415 (2001). [13] V Ranjan, R K Pandey, Manoj K Harbola and Vijay A Singh, Phys. Rev.

  13. Resonant inelastic scattering in dilute magnetic semiconductors by x-ray fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lawniczak-Jablonska, K. [Lawrence Berkeley National Lab., CA (United States)]|[Institute of Physics, Warsaw (Poland); Jia, J.J.; Underwood, J.H. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    As modern, technologically important materials have become more complex, element specific techniques have become invaluable in studying the electronic structure of individual components from the system. Soft x-ray fluorescence (SXF) and absorption (SXA) spectroscopies provide a unique means of measuring element and angular momentum density of electron states, respectively, for the valence and conducting bands in complex materials. X-ray absorption and the decay through x-ray emission are generally assumed to be two independent one-photon processes. Recent studies, however have demonstrated that SXF excited near the absorption threshold generate an array of spectral features that depend on nature of materials, particularly on the localization of excited states in s and d-band solids and that these two processes can no be longer treated as independent. Resonant SXF offers thus the new way to study the dynamics of the distribution of electronic valence states in the presence of a hole which is bound to the electron low lying in the conduction band. This process can simulate the interaction between hole-electron pair in wide gap semiconductors. Therefore such studies can help in understanding of transport and optics phenomena in the wide gap semiconductors. The authors report the result of Mn and S L-resonant emission in Zn{sub 1{minus}x}Mn{sub x}S (with x=0.2 and 0.3) and MnS as the energy of exciting radiation is tuned across the Mn and S L{sub 3,2} absorption edge, along with the resonant excited spectra from elemental Mn as a reference.

  14. Chemical Design and Example of Transparent Bipolar Semiconductors.

    Science.gov (United States)

    Arai, Takeshi; Iimura, Soshi; Kim, Junghwan; Toda, Yoshitake; Ueda, Shigenori; Hosono, Hideo

    2017-11-29

    Transparent bipolar semiconductors (TBSCs) are in demand for transparent electronics to serve as the basis for next generation optoelectronic devices. However, the poor carrier controllability in wide-bandgap materials makes the realization of a bipolar nature difficult. Only two materials, CuInO2 and SnO, have been reported as TBSCs. To satisfy demand for the coexistence of transparency and bipolarity, we propose a design concept with three strategies; choice of early transition metals (eTM) such as Y3+ and Zr4+ for improving controllability of carrier doping, design of chemical bonds to obtain an appropriate band structure for bipolar doping, and use of a forbidden band-edge transition to retain transparency. This approach is verified through a practical examination of a candidate material, tetragonal ZrOS, which is chosen by following the criteria. ZrOS exhibits an excellent controllability of the electrical conductivity (10-7-10-2 S cm-1), p- or n-type nature with ∼10-2 S cm-1 by Y or F doping, respectively, and optically wide gap (below 10-4 cm-1 up to ∼2.5 eV). This concept provides a new kind of TBSC based on eTM ionic compounds.

  15. Basic semiconductor physics

    CERN Document Server

    Hamaguchi, Chihiro

    2017-01-01

    This book presents a detailed description of basic semiconductor physics. The text covers a wide range of important phenomena in semiconductors, from the simple to the advanced. Four different methods of energy band calculations in the full band region are explained: local empirical pseudopotential, non-local pseudopotential, KP perturbation and tight-binding methods. The effective mass approximation and electron motion in a periodic potential, Boltzmann transport equation and deformation potentials used for analysis of transport properties are discussed. Further, the book examines experiments and theoretical analyses of cyclotron resonance in detail. Optical and transport properties, magneto-transport, two-dimensional electron gas transport (HEMT and MOSFET) and quantum transport are reviewed, while optical transition, electron-phonon interaction and electron mobility are also addressed. Energy and electronic structure of a quantum dot (artificial atom) are explained with the help of Slater determinants. The...

  16. Compound semiconductor device modelling

    CERN Document Server

    Miles, Robert

    1993-01-01

    Compound semiconductor devices form the foundation of solid-state microwave and optoelectronic technologies used in many modern communication systems. In common with their low frequency counterparts, these devices are often represented using equivalent circuit models, but it is often necessary to resort to physical models in order to gain insight into the detailed operation of compound semiconductor devices. Many of the earliest physical models were indeed developed to understand the 'unusual' phenomena which occur at high frequencies. Such was the case with the Gunn and IMPATI diodes, which led to an increased interest in using numerical simulation methods. Contemporary devices often have feature sizes so small that they no longer operate within the familiar traditional framework, and hot electron or even quantum­ mechanical models are required. The need for accurate and efficient models suitable for computer aided design has increased with the demand for a wider range of integrated devices for operation at...

  17. Single frequency semiconductor lasers

    CERN Document Server

    Fang, Zujie; Chen, Gaoting; Qu, Ronghui

    2017-01-01

    This book systematically introduces the single frequency semiconductor laser, which is widely used in many vital advanced technologies, such as the laser cooling of atoms and atomic clock, high-precision measurements and spectroscopy, coherent optical communications, and advanced optical sensors. It presents both the fundamentals and characteristics of semiconductor lasers, including basic F-P structure and monolithic integrated structures; interprets laser noises and their measurements; and explains mechanisms and technologies relating to the main aspects of single frequency lasers, including external cavity lasers, frequency stabilization technologies, frequency sweeping, optical phase locked loops, and so on. It paints a clear, physical picture of related technologies and reviews new developments in the field as well. It will be a useful reference to graduate students, researchers, and engineers in the field.

  18. Semiconductor physics an introduction

    CERN Document Server

    Seeger, Karlheinz

    1999-01-01

    Semiconductor Physics - An Introduction - is suitable for the senior undergraduate or new graduate student majoring in electrical engineering or physics. It will also be useful to solid-state scientists and device engineers involved in semiconductor design and technology. The text provides a lucid account of charge transport, energy transport and optical processes, and a detailed description of many devices. It includes sections on superlattices and quantum well structures, the effects of deep-level impurities on transport, the quantum Hall effect and the calculation of the influence of a magnetic field on the carrier distribution function. This 6th edition has been revised and corrected, and new sections have been added to different chapters.

  19. Infrared Semiconductor Metamaterials

    Science.gov (United States)

    2016-09-01

    AFRL-AFOSR-VA-TR-2016-0310 Infrared Semiconductor Metamaterials Jon Schuller UNIVERSITY OF CALIFORNIA SANTA BARBARA 3227 CHEADLE HL SANTA BARBARA, CA...S) AND ADDRESS(ES) University of California , Santa Barbara Office of Research, 3227 Cheadle Hall Santa Barbara, CA 93106-2050 8. PERFORMING...Using Heterojunction Resonators. Advanced Optical Materials, available online (2016). New discoveries, inventions, or patent disclosures: Do you have

  20. Nonradiative recombination in semiconductors

    CERN Document Server

    Abakumov, VN; Yassievich, IN

    1991-01-01

    In recent years, great progress has been made in the understandingof recombination processes controlling the number of excessfree carriers in semiconductors under nonequilibrium conditions. As a result, it is now possible to give a comprehensivetheoretical description of these processes. The authors haveselected a number of experimental results which elucidate theunderlying physical problems and enable a test of theoreticalmodels. The following topics are dealt with: phenomenological theory ofrecombination, theoretical models of shallow and deep localizedstates, cascade model of carrier captu

  1. Hole crystallization in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bonitz, M [Institut fuer Theoretische Physik und Astrophysik, Christian-Albrechts-Universitaet Kiel, 24098 Kiel (Germany); Filinov, V S [Institut fuer Theoretische Physik und Astrophysik, Christian-Albrechts-Universitaet Kiel, 24098 Kiel (Germany); Fortov, V E [Institute for High Energy Density, Russian Academy of Sciences, Izhorskay 13/19, Moscow 127412 (Russian Federation); Levashov, P R [Institute for High Energy Density, Russian Academy of Sciences, Izhorskay 13/19, Moscow 127412 (Russian Federation); Fehske, H [Institut fuer Physik, Universitaet Greifswald, l7487 Greifswald (Germany)

    2006-04-28

    When electrons in a solid are excited to a higher energy band they leave behind a vacancy (hole) in the original band which behaves like a positively charged particle. Here we predict that holes can spontaneously order into a regular lattice in semiconductors with sufficiently flat valence bands. The critical hole to electron effective mass ratio required for this phase transition is found to be of the order of 80.

  2. Hole crystallization in semiconductors

    OpenAIRE

    Bonitz, M.; Filinov, V. S.; Fortov, V. E.; Levashov, P. R.; Fehske, H.

    2005-01-01

    When electrons in a solid are excited to a higher energy band they leave behind a vacancy (hole) in the original band which behaves like a positively charged particle. Here we predict that holes can spontaneously order into a regular lattice in semiconductors with sufficiently flat valence bands. The critical hole to electron effective mass ratio required for this phase transition is found to be of the order of 80.

  3. Survey of semiconductor physics

    CERN Document Server

    Böer, Karl W

    1992-01-01

    Any book that covers a large variety of subjects and is written by one author lacks by necessity the depth provided by an expert in his or her own field of specialization. This book is no exception. It has been written with the encouragement of my students and colleagues, who felt that an extensive card file I had accumulated over the years of teaching solid state and semiconductor physics would be helpful to more than just a few of us. This file, updated from time to time, contained lecture notes and other entries that were useful in my research and permitted me to give to my students a broader spectrum of information than is available in typical textbooks. When assembling this material into a book, I divided the top­ ics into material dealing with the homogeneous semiconductor, the subject of the previously published Volume 1, and the inhomoge­ neous semiconductor, the subject of this Volume 2. In order to keep the book to a manageable size, sections of tutorial character which can be used as text for a g...

  4. Electrodes for Semiconductor Gas Sensors

    Science.gov (United States)

    Lee, Sung Pil

    2017-01-01

    The electrodes of semiconductor gas sensors are important in characterizing sensors based on their sensitivity, selectivity, reversibility, response time, and long-term stability. The types and materials of electrodes used for semiconductor gas sensors are analyzed. In addition, the effect of interfacial zones and surface states of electrode–semiconductor interfaces on their characteristics is studied. This study describes that the gas interaction mechanism of the electrode–semiconductor interfaces should take into account the interfacial zone, surface states, image force, and tunneling effect. PMID:28346349

  5. Method of passivating semiconductor surfaces

    Science.gov (United States)

    Wanlass, M.W.

    1990-06-19

    A method is described for passivating Group III-V or II-VI semiconductor compound surfaces. The method includes selecting a passivating material having a lattice constant substantially mismatched to the lattice constant of the semiconductor compound. The passivating material is then grown as an ultrathin layer of passivating material on the surface of the Group III-V or II-VI semiconductor compound. The passivating material is grown to a thickness sufficient to maintain a coherent interface between the ultrathin passivating material and the semiconductor compound. In addition, a device formed from such method is also disclosed.

  6. Layered semiconductor neutron detectors

    Science.gov (United States)

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  7. Hydrogen in semiconductors

    CERN Document Server

    Pankove, Jacques I

    1991-01-01

    Hydrogen plays an important role in silicon technology, having a profound effect on a wide range of properties. Thus, the study of hydrogen in semiconductors has received much attention from an interdisciplinary assortment of researchers. This sixteen-chapter volume provides a comprehensive review of the field, including a discussion of hydrogenation methods, the use of hydrogen to passivate defects, the use of hydrogen to neutralize deep levels, shallow acceptors and shallow donors in silicon, vibrational spectroscopy, and hydrogen-induced defects in silicon. In addition to this detailed cove

  8. Physics of Organic Semiconductors

    CERN Document Server

    Brütting, Wolfgang

    2005-01-01

    Filling the gap in the literature currently available, this book presents an overview of our knowledge of the physics behind organic semiconductor devices. Contributions from 18 international research groups cover various aspects of this field, ranging from the growth of organic layers and crystals, their electronic properties at interfaces, their photophysics and electrical transport properties to the application of these materials in such different devices as organic field-effect transistors, photovoltaic cells and organic light-emitting diodes. From the contents:. * Excitation Dynamics in O

  9. Band structure of semiconductors

    CERN Document Server

    Tsidilkovski, I M

    2013-01-01

    Band Structure of Semiconductors provides a review of the theoretical and experimental methods of investigating band structure and an analysis of the results of the developments in this field. The book presents the problems, methods, and applications in the study of band structure. Topics on the computational methods of band structure; band structures of important semiconducting materials; behavior of an electron in a perturbed periodic field; effective masses and g-factors for the most commonly encountered band structures; and the treatment of cyclotron resonance, Shubnikov-de Haas oscillatio

  10. Basic properties of semiconductors

    CERN Document Server

    Landsberg, PT

    2013-01-01

    Since Volume 1 was published in 1982, the centres of interest in the basic physics of semiconductors have shifted. Volume 1 was called Band Theory and Transport Properties in the first edition, but the subject has broadened to such an extent that Basic Properties is now a more suitable title. Seven chapters have been rewritten by the original authors. However, twelve chapters are essentially new, with the bulk of this work being devoted to important current topics which give this volume an almost encyclopaedic form. The first three chapters discuss various aspects of modern band theory and the

  11. Doped semiconductor nanocrystal junctions

    Energy Technology Data Exchange (ETDEWEB)

    Borowik, Ł.; Mélin, T., E-mail: thierry.melin@isen.iemn.univ-lille1.fr [Institut d’Electronique, de Microélectronique et de Nanotechnologie, CNRS-UMR8520, Avenue Poincaré, F-59652 Villeneuve d’Ascq (France); Nguyen-Tran, T.; Roca i Cabarrocas, P. [Laboratoire de Physique des Interfaces et des Couches Minces, CNRS-UMR7647, Ecole Polytechnique, F-91128 Palaiseau (France)

    2013-11-28

    Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (N{sub D}≈10{sup 20}−10{sup 21}cm{sup −3}) silicon nanocrystals (NCs) in the 2–50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple phenomenological law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as N{sub D}{sup −1/3}, and depleted charge linearly increasing with the NC diameter and varying as N{sub D}{sup 1/3}. We thus establish a “nanocrystal counterpart” of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.

  12. Squeezed light in semiconductors

    CERN Document Server

    Ward, M B

    2001-01-01

    Experimental evidence is presented for the generation of photon-number squeezed states of light as a result of multi-photon absorption. Photon-number squeezing as a result of non-linear absorption has long been predicted and results have been obtained utilising two very different material systems: (i) an AIGaAs waveguide in which high optical intensities can be maintained over a relatively long interaction length of 2 mm; (ii) the organic polymer p-toluene sulphonate polydiacetylene that is essentially a one-dimensional semiconductor possessing a highly nonlinear optical susceptibility. The resulting nonlinear absorption is shown to leave the transmitted light in a state that is clearly nonclassical, exhibiting photon-number fluctuations below the shot-noise limit. Tuning the laser wavelength across the half-bandgap energy has enabled a comparison between two- and three-photon processes in the semiconductor waveguide. The correlations created between different spectral components of a pulsed beam of light as ...

  13. II-VI semiconductor compounds

    CERN Document Server

    1993-01-01

    For condensed matter physicists and electronic engineers, this volume deals with aspects of II-VI semiconductor compounds. Areas covered include devices and applications of II-VI compounds; Co-based II-IV semi-magnetic semiconductors; and electronic structure of strained II-VI superlattices.

  14. Variable temperature semiconductor film deposition

    Science.gov (United States)

    Li, X.; Sheldon, P.

    1998-01-27

    A method of depositing a semiconductor material on a substrate is disclosed. The method sequentially comprises (a) providing the semiconductor material in a depositable state such as a vapor for deposition on the substrate; (b) depositing the semiconductor material on the substrate while heating the substrate to a first temperature sufficient to cause the semiconductor material to form a first film layer having a first grain size; (c) continually depositing the semiconductor material on the substrate while cooling the substrate to a second temperature sufficient to cause the semiconductor material to form a second film layer deposited on the first film layer and having a second grain size smaller than the first grain size; and (d) raising the substrate temperature, while either continuing or not continuing to deposit semiconductor material to form a third film layer, to thereby anneal the film layers into a single layer having favorable efficiency characteristics in photovoltaic applications. A preferred semiconductor material is cadmium telluride deposited on a glass/tin oxide substrate already having thereon a film layer of cadmium sulfide.

  15. Process for producing chalcogenide semiconductors

    Science.gov (United States)

    Noufi, R.; Chen, Y.W.

    1985-04-30

    A process for producing chalcogenide semiconductor material is disclosed. The process includes forming a base metal layer and then contacting this layer with a solution having a low pH and containing ions from at least one chalcogen to chalcogenize the layer and form the chalcogenide semiconductor material.

  16. Semiconductor materials and their properties

    NARCIS (Netherlands)

    Reinders, Angelina H.M.E.; Verlinden, Pierre; van Sark, Wilfried; Freundlich, Alexandre; Reinders, Angele; Verlinden, Pierre; van Sark, Wilfried; Freundlich, Alexandre

    2017-01-01

    Semiconductor materials are the basic materials which are used in photovoltaic (PV) devices. This chapter introduces solid-state physics and semiconductor properties that are relevant to photovoltaics without spending too much time on unnecessary information. Usually atoms in the group of

  17. Semiconductor photocatalysis principles and applications

    CERN Document Server

    Kisch, Horst

    2014-01-01

    Focusing on the basic principles of semiconductor photocatalysis, this book also gives a brief introduction to photochemistry, photoelectrochemistry, and homogeneous photocatalysis. In addition, the author - one of the leading authorities in the field - presents important environmental and practical aspects. A valuable, one-stop source for all chemists, material scientists, and physicists working in this area, as well as novice researchers entering semiconductor photocatalysis.

  18. Luminescence studies of semiconductor electrodes

    NARCIS (Netherlands)

    Kelly, J.J.; Kooij, Ernst S.; Meulenkamp, E.A.

    1999-01-01

    In this paper we review our recent results of in-situ luminescence studies of semiconductor electrodes. Three classes of materials are considered: single crystal compound semiconductors, porous silicon and semiconducting oxides doped with luminescent ions. We show how photoluminescence (PL) and

  19. Organic semiconductors in a spin

    CERN Document Server

    Samuel, I

    2002-01-01

    A little palladium can go a long way in polymer-based light-emitting diodes. Inorganic semiconductors such as silicon and gallium arsenide are essential for countless applications in everyday life, ranging from PCs to CD players. However, while they offer unrivalled computational speed, inorganic semiconductors are also rigid and brittle, which means that they are less suited to applications such as displays and flexible electronics. A completely different class of materials - organic semiconductors - are being developed for these applications. Organic semiconductors have many attractive features: they are easy to make, they can emit visible light, and there is tremendous scope for tailoring their properties to specific applications by changing their chemical structure. Research groups and companies around the world have developed a wide range of organic-semiconductor devices, including transistors, light-emitting diodes (LEDs), solar cells and lasers. (U.K.)

  20. Photocatalysis Using Semiconductor Nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Thurston, T.R.; Wilcoxon,J.P.

    1999-01-21

    We report on experiments using nanosize MoS{sub 2} to photo-oxidize organic pollutants in water using visible light as the energy source. We have demonstrated that we can vary the redox potentials and absorbance characteristics of these small semiconductors by adjusting their size, and our studies of the photooxidation of organic molecules have revealed that the rate of oxidation increases with increasing bandgap (i.e. more positive valence band and more negative conduction band potentials). Because these photocatalysis reactions can be performed with the nanoclusters fully dispersed and stable in solution, liquid chromatography can be used to determine both the intermediate reaction products and the state of the nanoclusters during the reaction. We have demonstrated that the MoS{sub 2} nanoclusters remain unchanged during the photooxidation process by this technique. We also report on studies of MoS{sub 2} nanoclusters deposited on TiO{sub 2} powder.

  1. Semiconductor radiation detector

    Science.gov (United States)

    Bell, Zane W.; Burger, Arnold

    2010-03-30

    A semiconductor detector for ionizing electromagnetic radiation, neutrons, and energetic charged particles. The detecting element is comprised of a compound having the composition I-III-VI.sub.2 or II-IV-V.sub.2 where the "I" component is from column 1A or 1B of the periodic table, the "II" component is from column 2B, the "III" component is from column 3A, the "IV" component is from column 4A, the "V" component is from column 5A, and the "VI" component is from column 6A. The detecting element detects ionizing radiation by generating a signal proportional to the energy deposited in the element, and detects neutrons by virtue of the ionizing radiation emitted by one or more of the constituent materials subsequent to capture. The detector may contain more than one neutron-sensitive component.

  2. Semiconductor optoelectronic infrared spectroscopy

    CERN Document Server

    Hollingworth, A R

    2001-01-01

    level separation. This showed for the first time evidence of the phonon bottleneck in a working laser device. A new technique called time resolved optically detected cyclotron resonance, was used as a precursor to finding the carrier dynamics within a spatially confined quantum dot. By moving to the case of a spatial QD using an optically detected intraband resonance it was possible to measure the energy separation interband levels and conduction and valence sublevels within the dot simultaneously. Furthermore this technique has been shown that the inhomogeneous broadening of the photoluminescence spectrum is not purely affected by just size and composition. We suggest that other processes such as state occupancy, In roughing, and exciton binding energies may account for the extra energy. We use spectroscopy to study infrared optoelectronic inter and intraband semiconductor carrier dynamics. The overall aim of this thesis was to study both III-V and Pb chalcogenide material systems in order to show their futu...

  3. Semiconductor adiabatic qubits

    Energy Technology Data Exchange (ETDEWEB)

    Carroll, Malcolm S.; Witzel, Wayne; Jacobson, Noah Tobias; Ganti, Anand; Landahl, Andrew J.; Lilly, Michael; Nguyen, Khoi Thi; Bishop, Nathaniel; Carr, Stephen M.; Bussmann, Ezra; Nielsen, Erik; Levy, James Ewers; Blume-Kohout, Robin J.; Rahman, Rajib

    2016-12-27

    A quantum computing device that includes a plurality of semiconductor adiabatic qubits is described herein. The qubits are programmed with local biases and coupling terms between qubits that represent a problem of interest. The qubits are initialized by way of a tuneable parameter, a local tunnel coupling within each qubit, such that the qubits remain in a ground energy state, and that initial state is represented by the qubits being in a superposition of |0> and |1> states. The parameter is altered over time adiabatically or such that relaxation mechanisms maintain a large fraction of ground state occupation through decreasing the tunnel coupling barrier within each qubit with the appropriate schedule. The final state when tunnel coupling is effectively zero represents the solution state to the problem represented in the |0> and |1> basis, which can be accurately read at each qubit location.

  4. Unraveling the Origin of Magnetism in Mesoporous Cu-Doped SnO2 Magnetic Semiconductors

    Directory of Open Access Journals (Sweden)

    Junpeng Fan

    2017-10-01

    Full Text Available The origin of magnetism in wide-gap semiconductors doped with non-ferromagnetic 3d transition metals still remains intriguing. In this article, insights in the magnetic properties of ordered mesoporous Cu-doped SnO2 powders, prepared by hard-templating, have been unraveled. Whereas, both oxygen vacancies and Fe-based impurity phases could be a plausible explanation for the observed room temperature ferromagnetism, the low temperature magnetism is mainly and unambiguously arising from the nanoscale nature of the formed antiferromagnetic CuO, which results in a net magnetization that is reminiscent of ferromagnetic behavior. This is ascribed to uncompensated spins and shape-mediated spin canting effects. The reduced blocking temperature, which resides between 30 and 5 K, and traces of vertical shifts in the hysteresis loops confirm size effects in CuO. The mesoporous nature of the system with a large surface-to-volume ratio likely promotes the occurrence of uncompensated spins, spin canting, and spin frustration, offering new prospects in the use of magnetic semiconductors for energy-efficient spintronics.

  5. Self-regulation of charged defect compensation and formation energy pinning in semiconductors.

    Science.gov (United States)

    Yang, Ji-Hui; Yin, Wan-Jian; Park, Ji-Sang; Wei, Su-Huai

    2015-11-20

    Current theoretical analyses of defect properties without solving the detailed balance equations often estimate Fermi-level pinning position by omitting free carriers and assume defect concentrations can be always tuned by atomic chemical potentials. This could be misleading in some circumstance. Here we clarify that: (1) Because the Fermi-level pinning is determined not only by defect states but also by free carriers from band-edge states, band-edge states should be treated explicitly in the same footing as the defect states in practice; (2) defect formation energy, thus defect density, could be pinned and independent on atomic chemical potentials due to the entanglement of atomic chemical potentials and Fermi energy, in contrast to the usual expectation that defect formation energy can always be tuned by varying the atomic chemical potentials; and (3) the charged defect compensation behavior, i.e., most of donors are compensated by acceptors or vice versa, is self-regulated when defect formation energies are pinned. The last two phenomena are more dominant in wide-gap semiconductors or when the defect formation energies are small. Using NaCl and CH3NH3PbI3 as examples, we illustrate these unexpected behaviors. Our analysis thus provides new insights that enrich the understanding of the defect physics in semiconductors and insulators.

  6. Unraveling the Origin of Magnetism in Mesoporous Cu-Doped SnO₂ Magnetic Semiconductors.

    Science.gov (United States)

    Fan, Junpeng; Menéndez, Enric; Guerrero, Miguel; Quintana, Alberto; Weschke, Eugen; Pellicer, Eva; Sort, Jordi

    2017-10-25

    The origin of magnetism in wide-gap semiconductors doped with non-ferromagnetic 3d transition metals still remains intriguing. In this article, insights in the magnetic properties of ordered mesoporous Cu-doped SnO₂ powders, prepared by hard-templating, have been unraveled. Whereas, both oxygen vacancies and Fe-based impurity phases could be a plausible explanation for the observed room temperature ferromagnetism, the low temperature magnetism is mainly and unambiguously arising from the nanoscale nature of the formed antiferromagnetic CuO, which results in a net magnetization that is reminiscent of ferromagnetic behavior. This is ascribed to uncompensated spins and shape-mediated spin canting effects. The reduced blocking temperature, which resides between 30 and 5 K, and traces of vertical shifts in the hysteresis loops confirm size effects in CuO. The mesoporous nature of the system with a large surface-to-volume ratio likely promotes the occurrence of uncompensated spins, spin canting, and spin frustration, offering new prospects in the use of magnetic semiconductors for energy-efficient spintronics.

  7. Semiconductor-superconductor optoelectronic devices

    Science.gov (United States)

    Bouscher, Shlomi; Panna, Dmitry; Hayat, Alex

    2017-10-01

    Devices combining superconductors with semiconductors offer a wide range of applications, particularly in the growing field of quantum information processing. This is due to their ability to take advantage of both the extensive knowledge gathered in the field of semiconductors and the unique quantum properties of superconductors. This results in novel device concepts, such as structures generating and detecting entangled photon pairs as well as novel optical gain and laser realizations. In this review, we discuss the fundamental concepts and the underlying physical phenomena of superconductor-semiconductor optoelectronics as well as practical device implementations.

  8. Semiconductor Nanocrystals for Biological Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Aihua; Gu, Weiwei; Larabell, Carolyn; Alivisatos, A. Paul

    2005-06-28

    Conventional organic fluorophores suffer from poor photo stability, narrow absorption spectra and broad emission feature. Semiconductor nanocrystals, on the other hand, are highly photo-stable with broad absorption spectra and narrow size-tunable emission spectra. Recent advances in the synthesis of these materials have resulted in bright, sensitive, extremely photo-stable and biocompatible semiconductor fluorophores. Commercial availability facilitates their application in a variety of unprecedented biological experiments, including multiplexed cellular imaging, long-term in vitro and in vivo labeling, deep tissue structure mapping and single particle investigation of dynamic cellular processes. Semiconductor nanocrystals are one of the first examples of nanotechnology enabling a new class of biomedical applications.

  9. Effect of van der Waals interaction on the properties of SnS{sub 2} layered semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Seminovski, Y. [Instituto de Energía Solar, Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Dpt. TEAT, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Palacios, P., E-mail: pablo.palacios@upm.es [Instituto de Energía Solar, Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Dpt. FyQATA, EIAE, Universidad Politécnica de Madrid, Pz. Cardenal Cisneros, 3, 28040 Madrid (Spain); Wahnón, P. [Instituto de Energía Solar, Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Dpt. TEAT, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain)

    2013-05-01

    Nowadays, dispersion correction applied on layered semiconductors is a topic of interest. Among the known layered semiconductors, SnS{sub 2} polytypes are wide gap semiconductors with a van der Waals interaction between their layers, which could form good materials to be used in photovoltaic applications. The present work gives an approach to the SnS{sub 2} geometrical and electronic characterization using an empirical dispersion correction added to the Perdew–Burke–Ernzerhof functional and subsequent actualization of the electronic charge density using the screened hybrid Heyd–Scuseria–Ernzerhof functional using a density functional code. The obtained interlayer distance and band-gap are in good agreement with experimental values when van der Waals dispersion forces are included. - Highlights: ► Tin disulphide (SnS{sub 2}) has been calculated using density functional theory methods. ► A dispersion correction was also applied for two different SnS{sub 2} polytypes. ► Geometrical parameters and band-gaps were obtained using both approaches. ► Our calculations give a good agreement of the computed band gap with experiment.

  10. Toward designing semiconductor-semiconductor heterojunctions for photocatalytic applications

    Science.gov (United States)

    Zhang, Liping; Jaroniec, Mietek

    2018-02-01

    Semiconductor photocatalysts show a great potential for environmental and energy-related applications, however one of the major disadvantages is their relatively low photocatalytic performance due to the recombination of electron-hole pairs. Therefore, intensive research is being conducted toward design of heterojunctions, which have been shown to be effective for improving the charge-transfer properties and efficiency of photocatalysts. According to the type of band alignment and direction of internal electric field, heterojunctions are categorized into five different types, each of which is associated with its own charge transfer characteristics. Since the design of heterojunctions requires the knowledge of band edge positions of component semiconductors, the commonly used techniques for the assessment of band edge positions are reviewed. Among them the electronegativity-based calculation method is applied for a large number of popular visible-light-active semiconductors, including some widely investigated bismuth-containing semiconductors. On basis of the calculated band edge positions and the type of component semiconductors reported, heterojunctions composed of the selected bismuth-containing semiconductors are proposed. Finally, the most popular synthetic techniques for the fabrication of heterojunctions are briefly discussed.

  11. Atomic layer deposition for semiconductors

    CERN Document Server

    Hwang, Cheol Seong

    2014-01-01

    This edited volume discusses atomic layer deposition (ALD) for all modern semiconductor devices, moving from the basic chemistry of ALD and modeling of ALD processes to sections on ALD for memories, logic devices, and machines.

  12. Semiconductor radiation detectors. Device physics

    Energy Technology Data Exchange (ETDEWEB)

    Lutz, G. [Max-Planck-Institutes for Physics and Extraterrestrial Physics, Muenchen (Germany). Semiconductor Lab.

    2007-07-01

    Starting from basic principles, the author, whose own contributions to these developments have been significant, describes the rapidly growing field of modern semiconductor detectors used for energy and position measurement radiation. This development was stimulated by requirements in elementary particle physics where it has led to important scientific discoveries. It has now spread to many other fields of science and technology. The book is written in a didactic way and includes an introduction to semiconductor physics. The working principles of semiconductor radiation detectors are explained in an intuitive way, followed by formal quantitative analysis. Broad coverage is also given to electronic signal readout and to the subject of radiation damage. The book is the first to comprehensively cover the semiconductor radiation detectors currently in use. It is useful as a teaching guide and as a reference work for research and applications. (orig.)

  13. Physics of semiconductor laser devices

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, G.H.B.

    1980-01-01

    Aspects of laser design and development are considered along with semiconductor materials for lasers, problems of device fabrication, crystal growth, the degradation of lasers, and the integration of semiconductor lasers with other optical components. A description is presented of light emission processes and laser action in semiconductors, taking into account electronic radiative transitions, the relation between emission and absorption processes, transition probabilities, the density of electron states in the highly doped semiconductor, carrier recombination and spontaneous emission, the gain/current relation, light-current characteristics, optical modes, and the evolution of mode spectrum and intensity with current. Attention is given to laser heterostructures and the properties of heterojunctions, optical waveguides, the performance of heterostructure lasers, stripe geometry lasers, and the dynamic response of lasers. Lasers with distributed feedback and Bragg reflectors are also discussed.

  14. Energy transfer with semiconductor nanocrystals

    NARCIS (Netherlands)

    Rogach, A.L.; Klar, T.A.; Lupton, J.M.; Meijerink, A.; Feldmann, J.

    2009-01-01

    Fo¨ rster (or fluorescence) resonant energy transfer (FRET) is a powerful spectroscopic technique to study interactions, conformational and distance changes, in hybrid nanosystems. Semiconductor nanocrystals, also known as colloidal quantum dots, are highly efficient fluorophores with a strong

  15. Ballistic superconductivity in semiconductor nanowires

    NARCIS (Netherlands)

    Zhang, H.; Gül, Ö.; Conesa-Boj, S.; Nowak, M.P.; Wimmer, M.; Zuo, K.; Mourik, V.; Vries, F.K. de; Veen, J. van; Moor, M.W.A. de; Bommer, J.D.S.; Woerkom, D.J. van; Car, D.; Plissard, S.R.; Bakkers, E.P.A.M.; Quintero Pérez, M.; Cassidy, M.C.; Koelling, S.; Goswami, S.; Watanabe, K.; Taniguchi, T.; Kouwenhoven, L.P.

    2017-01-01

    Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of

  16. Quantum optics with semiconductor nanostructures

    CERN Document Server

    Jahnke, Frank

    2012-01-01

    A guide to the theory, application and potential of semiconductor nanostructures in the exploration of quantum optics. It offers an overview of resonance fluorescence emission.$bAn understanding of the interaction between light and matter on a quantum level is of fundamental interest and has many applications in optical technologies. The quantum nature of the interaction has recently attracted great attention for applications of semiconductor nanostructures in quantum information processing. Quantum optics with semiconductor nanostructures is a key guide to the theory, experimental realisation, and future potential of semiconductor nanostructures in the exploration of quantum optics. Part one provides a comprehensive overview of single quantum dot systems, beginning with a look at resonance fluorescence emission. Quantum optics with single quantum dots in photonic crystal and micro cavities are explored in detail, before part two goes on to review nanolasers with quantum dot emitters. Light-matter interaction...

  17. Semiconductor nanocrystals or quantum dots

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 18; Issue 8. Various Quantum Mechanical Concepts for Confinements in Semiconductor Nanocrystals. Jayakrishna Khatei Karuna Kar Nanda. Classroom Volume 18 Issue 8 August 2013 pp 771-776 ...

  18. Semiconductor packaging materials interaction and reliability

    CERN Document Server

    Chen, Andrea

    2012-01-01

    In semiconductor manufacturing, understanding how various materials behave and interact is critical to making a reliable and robust semiconductor package. Semiconductor Packaging: Materials Interaction and Reliability provides a fundamental understanding of the underlying physical properties of the materials used in a semiconductor package. The book focuses on an important step in semiconductor manufacturing--package assembly and testing. It covers the basics of material properties and explains how to determine which behaviors are important to package performance. The authors also discuss how

  19. Fractal properties of nanostructured semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhanabaev, Z.Zh. [Al-Farabi Khazakh National University, Tole bi Street, 96, Almaty 050012 (Kazakhstan); Grevtseva, T.Yu. [Al-Farabi Khazakh National University, Tole bi Street, 96, Almaty 050012 (Kazakhstan)]. E-mail: kenwp@mail.ru

    2007-03-15

    A theory for the temperature and time dependence of current carrier concentration in semiconductors with different non-equilibrium nanocluster structure has been developed. It was shown that the scale-invariant fractal self-similar and self-affine laws can exist near by the transition point to the equilibrium state. Results of the theory have been compared to the experimental data from electrical properties of semiconductor films with nanoclusters.

  20. Dissipative chaos in semiconductor superlattices

    Directory of Open Access Journals (Sweden)

    F. Moghadam

    2008-03-01

    Full Text Available In this paper the motion of electron in a miniband of a semiconductor superlattice (SSL under the influence of external electric and magnetic fields is investigated. The electric field is applied in a direction perpendicular to the layers of the semiconductor superlattice, and the magnetic field is applied in different direction Numerical calculations show conditions led to the possibility of chaotic behaviors.

  1. Nonlinear Optical Interactions in Semiconductors.

    Science.gov (United States)

    1985-12-10

    Physique du Solide et Energie Solaire We had on-going interaction with Dr. Christian Verie on the growth of high quality narrow-gap semiconductor crystals...The band gap energy of the semiconductor decreases with increasing temperature. Consequently, the absorption of light in the energy region of the...gas and, more importantly, will modulate the electron energy at the difference frequency, wI - 02" Under ordinary circumstances such an energy (or

  2. Survey of cryogenic semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    Talarico, L.J.; McKeever, J.W.

    1996-04-01

    Improved reliability and electronic performance can be achieved in a system operated at cryogenic temperatures because of the reduction in mechanical insult and in disruptive effects of thermal energy on electronic devices. Continuing discoveries of new superconductors with ever increasing values of T{sub c} above that of liquid nitrogen temperature (LNT) have provided incentive for developing semiconductor electronic systems that may also operate in the superconductor`s liquid nitrogen bath. Because of the interest in high-temperature superconductor (HTS) devices, liquid nitrogen is the cryogen of choice and LNT is the temperature on which this review is focused. The purpose of this survey is to locate and assemble published information comparing the room temperature (298 K), performance of commercially available conventional and hybrid semiconductor device with their performance at LNT (77K), to help establish their candidacy as cryogenic electronic devices specifically for use at LNT. The approach to gathering information for this survey included the following activities. Periodicals and proceedings were searched for information on the behavior of semiconductor devices at LNT. Telephone calls were made to representatives of semiconductor industries, to semiconductor subcontractors, to university faculty members prominent for their research in the area of cryogenic semiconductors, and to representatives of the National Aeronautics and Space Administration (NASA) and NASA subcontractors. The sources and contacts are listed with their responses in the introduction, and a list of references appears at the end of the survey.

  3. The ATLAS semiconductor tracker

    CERN Document Server

    Mikuz, Marko

    2003-01-01

    The ATLAS Semiconductor Tracker (SCT) is presented. About 16000 silicon micro-strip sensors with a total active surface of over 60 m **2 and with 6.3 million read-out channels are built into 4088 modules arranged into four barrel layers and nine disks covering each of the forward regions up to an eta of 2.5. Challenges are imposed by the hostile radiation environment with particle fluences up to 2 multiplied by 10**1**4 cm**-**2 1 MeV neutron NIEL equivalent and 100 kGy TID, the 25 ns LHC bunch crossing time and the need for a hermetic, lightweight tracker. The solution adopted is carefully designed strip detectors operated at -7 degree C, biased up to 500 V and read out by binary radhard fast BiCMOS electronics. A zero-CTE carbon fibre structure provides mechanical support. 30 kW of power are supplied on aluminiutn/Kapton tapes and cooled by C//3F//8 evaporative cooling. Data and commands are transferred by optical links. Prototypes of detector modules have been built, irradiated to the maximum expected flue...

  4. Wide-Bandgap Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Chinthavali, M.S.

    2005-11-22

    With the increase in demand for more efficient, higher-power, and higher-temperature operation of power converters, design engineers face the challenge of increasing the efficiency and power density of converters [1, 2]. Development in power semiconductors is vital for achieving the design goals set by the industry. Silicon (Si) power devices have reached their theoretical limits in terms of higher-temperature and higher-power operation by virtue of the physical properties of the material. To overcome these limitations, research has focused on wide-bandgap materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond because of their superior material advantages such as large bandgap, high thermal conductivity, and high critical breakdown field strength. Diamond is the ultimate material for power devices because of its greater than tenfold improvement in electrical properties compared with silicon; however, it is more suited for higher-voltage (grid level) higher-power applications based on the intrinsic properties of the material [3]. GaN and SiC power devices have similar performance improvements over Si power devices. GaN performs only slightly better than SiC. Both SiC and GaN have processing issues that need to be resolved before they can seriously challenge Si power devices; however, SiC is at a more technically advanced stage than GaN. SiC is considered to be the best transition material for future power devices before high-power diamond device technology matures. Since SiC power devices have lower losses than Si devices, SiC-based power converters are more efficient. With the high-temperature operation capability of SiC, thermal management requirements are reduced; therefore, a smaller heat sink would be sufficient. In addition, since SiC power devices can be switched at higher frequencies, smaller passive components are required in power converters. Smaller heat sinks and passive components result in higher-power-density power converters

  5. Semiconductor lasers stability, instability and chaos

    CERN Document Server

    Ohtsubo, Junji

    2017-01-01

    This book describes the fascinating recent advances made concerning the chaos, stability and instability of semiconductor lasers, and discusses their applications and future prospects in detail. It emphasizes the dynamics in semiconductor lasers by optical and electronic feedback, optical injection, and injection current modulation. Applications of semiconductor laser chaos, control and noise, and semiconductor lasers are also demonstrated. Semiconductor lasers with new structures, such as vertical-cavity surface-emitting lasers and broad-area semiconductor lasers, are intriguing and promising devices. Current topics include fast physical number generation using chaotic semiconductor lasers for secure communication, development of chaos, quantum-dot semiconductor lasers and quantum-cascade semiconductor lasers, and vertical-cavity surface-emitting lasers. This fourth edition has been significantly expanded to reflect the latest developments. The fundamental theory of laser chaos and the chaotic dynamics in se...

  6. Structural characterization of the high-temperature modification of the Cu{sub 2}ZnGeTe{sub 4} quaternary semiconductor compound

    Energy Technology Data Exchange (ETDEWEB)

    Nieves, L.; Marcano, G.; Power, C.; Rincon, C. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101 (Venezuela, Bolivarian Republic of); Delgado, G.E. [Laboratorio de Cristalografia, Departamento de Quimica, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101 (Venezuela, Bolivarian Republic of); Lopez-Rivera, S.A. [Grupo de Fisica Aplicada, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101 (Venezuela, Bolivarian Republic of)

    2016-06-15

    A combined study of the X-ray powder diffraction, differential thermal analysis, optical absorption, and Raman spectroscopy of the high-temperature modification of Cu{sub 2}ZnGeTe{sub 4} quaternary semiconductor, obtained by fast quenching from 820 K to ice water temperature, has been done. It has been found that this phase crystallizes in a tetragonal kesterite-type structure. From the analysis of the absorption coefficient spectra, the band gap energy of this material at room temperature has been found to be 1.49 eV. An optical transition from defect acceptor states to the conduction band is also observed below the fundamental absorption edge. Three strongest Raman lines observed at 116, 119, and 139 cm{sup -1} have been assigned to the A-symmetry modes. Also, lines at 81, 89, 97, and 263 cm{sup -1} tentatively ascribed as B or E-symmetry modes have been detected from the spectrum. The presence in this high-temperature modification of ZnTe and Cu{sub 2}GeTe{sub 3} secondary phases has been detected by both XRD and Raman spectroscopy. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Photoreflectance Characterization of Semiconductors

    Science.gov (United States)

    Bhimnathwala, Hemant Ghanshyamdas

    Photoreflectance technique has been used as a non-destructive probe of surface photo-voltage in doped and semi-insulating semiconductors. A system used to measure the photoreflectance spectra near the fundamental gap of GaAs and InP has been described. Measurements as a function of pump intensity on n and p type GaAs were used to infer the carrier dynamics leading to change in the surface electric field. Measurements indicate that the surface of GaAs consists of hole traps at the surface in addition to recombination states. This is confirmed by spectroscopic studies carried out by varying the pump modulation frequency at fixed temperatures and the measurements show that the hole trap has an activation energy of 0.29 eV and has an emission time of 0.175 +/- 0.002 msec. at room temperature. In semi-insulating GaAs, it is expected that there is no surface electric field at equilibrium due to pinning at the surface and large concentration of deep defect EL2. Electromodulation, in this case proceeds via preferential trapping of holes at the surface. This is supported by measurements carried out as a function of pump intensity and on wafers having different carbon concentrations. Analysis of carrier dynamics in semi-insulating GaAs is much simplified by use of Nd:YAG laser (instead of a HeNe laser) as a source of pump beam. A sub-band -gap excitation generates mainly excess electrons and the Poisson's equation can be integrated once to find the surface electric field. Numerical integration yields the surface photovoltage. It is shown that this technique is sensitive to the the surface state density and relatively insensitive to bulk properties. It has been applied to study the effect of various chemical reactants on the surface state density. In many PR spectra, features at energies less than the gap energy are observed. These are ascribed to shallow acceptors unrelated to carbon, which was the dominant acceptor in these materials. It is proposed that the electric field

  8. Physics of semiconductor laser devices

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, G.H.B.

    1980-01-01

    The physics of the semiconductor laser is studied. The basic phenomena that control the operation of the device are analyzed and described in considerable detail. The treatment has been keyed particularly to fundamental concepts and kept general in order to avoid being overtaken by events. The range of phenomena in a semiconductor laser involves a number of scientific disciplines. To cater for the reader who is not already a specialist in all of these the author has endeavoured, in the chapters on fundamental behaviour, to provide in a readable form the minimum background that is needed to understand the more specialist part of the text. As an introduction a general review is given of the whole range of semiconductor laser devices that now exist, the technology involved in their fabrication, the factors that determine their reliability, and their possible role in integrated systems.

  9. Thiophene-Based Organic Semiconductors.

    Science.gov (United States)

    Turkoglu, Gulsen; Cinar, M Emin; Ozturk, Turan

    2017-10-24

    Thiophene-based π-conjugated organic small molecules and polymers are the research subject of significant current interest owing to their potential use as organic semiconductors in material chemistry. Despite simple and similar molecular structures, the hitherto reported properties of thiophene-based organic semiconductors are rather diverse. Design of high performance organic semiconducting materials requires a thorough understanding of inter- and intra-molecular interactions, solid-state packing, and the influence of both factors on the charge carrier transport. In this chapter, thiophene-based organic semiconductors, which are classified in terms of their chemical structures and their structure-property relationships, are addressed for the potential applications as organic photovoltaics (OPVs), organic field-effect transistors (OFETs) and organic light emitting diodes (OLEDs).

  10. High pressure semiconductor physics I

    CERN Document Server

    Willardson, R K; Paul, William; Suski, Tadeusz

    1998-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The "Willardson and Beer" Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices, Oxygen in Silicon, and others promise indeed that this tra...

  11. Semiconductor device physics and simulation

    CERN Document Server

    Yuan, J S

    1998-01-01

    This volume provides thorough coverage of modern semiconductor devices -including hetero- and homo-junction devices-using a two-dimensional simulator (MEDICI) to perform the analysis and generate simulation results Each device is examined in terms of dc, ac, and transient simulator results; relevant device physics; and implications for design and analysis Two hundred forty-four useful figures illustrate the physical mechanisms and characteristics of the devices simulated Comprehensive and carefully organized, Semiconductor Device Physics and Simulation is the ideal bridge from device physics to practical device design

  12. Optical coherent control in semiconductors

    DEFF Research Database (Denmark)

    Østergaard, John Erland; Vadim, Lyssenko; Hvam, Jørn Märcher

    2001-01-01

    The developments with coherent control (CC) techniques in optical spectroscopy have recently demonstrated population control and coherence manipulations when the induced optical phase is explored with phase-locked laser pulses. These and other developments have been guiding the new research field...... of quantum control including the recent applications to semiconductors and nanostructures. We study the influence of inhomogeneous broadening in semiconductors on CC results. Photoluminescence (PL) and the coherent emission in four-wave mixing (FWM) is recorded after resonant excitation with phase-locked...

  13. Semiconductor lasers and herterojunction leds

    CERN Document Server

    Kressel, Henry

    2012-01-01

    Semiconductor Lasers and Heterojunction LEDs presents an introduction to the subject of semiconductor lasers and heterojunction LEDs. The book reviews relevant basic solid-state and electromagnetic principles; the relevant concepts in solid state physics; and the p-n junctions and heterojunctions. The text also describes stimulated emission and gain; the relevant concepts in electromagnetic field theory; and the modes in laser structures. The relation between electrical and optical properties of laser diodes; epitaxial technology; binary III-V compounds; and diode fabrication are also consider

  14. Semiconductors and semimetals epitaxial microstructures

    CERN Document Server

    Willardson, Robert K; Beer, Albert C; Gossard, Arthur C

    1994-01-01

    Newly developed semiconductor microstructures can now guide light and electrons resulting in important consequences for state-of-the-art electronic and photonic devices. This volume introduces a new generation of epitaxial microstructures. Special emphasis has been given to atomic control during growth and the interrelationship between the atomic arrangements and the properties of the structures.Key Features* Atomic-level control of semiconductor microstructures* Molecular beam epitaxy, metal-organic chemical vapor deposition* Quantum wells and quantum wires* Lasers, photon(IR)detectors, heterostructure transistors

  15. Introduction to semiconductor manufacturing technology

    CERN Document Server

    2012-01-01

    IC chip manufacturing processes, such as photolithography, etch, CVD, PVD, CMP, ion implantation, RTP, inspection, and metrology, are complex methods that draw upon many disciplines. [i]Introduction to Semiconductor Manufacturing Technologies, Second Edition[/i] thoroughly describes the complicated processes with minimal mathematics, chemistry, and physics; it covers advanced concepts while keeping the contents accessible to readers without advanced degrees. Designed as a textbook for college students, this book provides a realistic picture of the semiconductor industry and an in-depth discuss

  16. Wide band gap semiconductor templates

    Energy Technology Data Exchange (ETDEWEB)

    Arendt, Paul N. (Los Alamos, NM); Stan, Liliana (Los Alamos, NM); Jia, Quanxi (Los Alamos, NM); DePaula, Raymond F. (Santa Fe, NM); Usov, Igor O. (Los Alamos, NM)

    2010-12-14

    The present invention relates to a thin film structure based on an epitaxial (111)-oriented rare earth-Group IVB oxide on the cubic (001) MgO terminated surface and the ion-beam-assisted deposition ("IBAD") techniques that are amendable to be over coated by semiconductors with hexagonal crystal structures. The IBAD magnesium oxide ("MgO") technology, in conjunction with certain template materials, is used to fabricate the desired thin film array. Similarly, IBAD MgO with appropriate template layers can be used for semiconductors with cubic type crystal structures.

  17. Modeling of semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Mørk, Jesper; Bischoff, Svend; Berg, Tommy Winther

    We discuss the modelling of semiconductor optical amplifiers with emphasis on their high-speed properties. Applications in linear amplification as well as ultrafast optical signal processing are reviewed. Finally, the possible role of quantum-dot based optical amplifiers is discussed.......We discuss the modelling of semiconductor optical amplifiers with emphasis on their high-speed properties. Applications in linear amplification as well as ultrafast optical signal processing are reviewed. Finally, the possible role of quantum-dot based optical amplifiers is discussed....

  18. Organic semiconductors in sensor applications

    CERN Document Server

    Malliaras, George; Owens, Róisín

    2008-01-01

    Organic semiconductors offer unique characteristics such as tunability of electronic properties via chemical synthesis, compatibility with mechanically flexible substrates, low-cost manufacturing, and facile integration with chemical and biological functionalities. These characteristics have prompted the application of organic semiconductors and their devices in physical, chemical, and biological sensors. This book covers this rapidly emerging field by discussing both optical and electrical sensor concepts. Novel transducers based on organic light-emitting diodes and organic thin-film transistors, as well as systems-on-a-chip architectures are presented. Functionalization techniques to enhance specificity are outlined, and models for the sensor response are described.

  19. Influence of phonons on semiconductor quantum emission

    Energy Technology Data Exchange (ETDEWEB)

    Feldtmann, Thomas

    2009-07-06

    A microscopic theory of interacting charge carriers, lattice vibrations, and light modes in semiconductor systems is presented. The theory is applied to study quantum dots and phonon-assisted luminescence in bulk semiconductors and heterostructures. (orig.)

  20. Fundamentals of semiconductors physics and materials properties

    CERN Document Server

    Yu, Peter Y

    2005-01-01

    Provides detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors. This textbook emphasizes understanding the physical properties of Si and similar tetrahedrally coordinated semiconductors and features an extensive collection of tables of material parameters, figures, and problems.

  1. Applications of semiconductor detectors to nuclear medicine

    CERN Document Server

    Bradford-Barber, H

    1999-01-01

    Progress in the development of semiconductor detectors is being applied to improving the resolution and imaging performance of nuclear medicine cameras. Nuclear medicine is briefly described. Efforts to develop semiconductor cameras for both planar and tomographic imaging are reviewed.

  2. One-sided rectifying p-n junction diodes fabricated from n-CdS and p-ZnTe:Te semiconductors

    Science.gov (United States)

    Olusola, O. I.; Salim, H. I.; Dharmadasa, I. M.

    2016-09-01

    The fabrication of a one-sided p-n hetero-junction (HJ) diodes have been successfully carried out using both p-type ZnTe and n-CdS semiconductors. Chemical bath deposition (CBD) and electrodeposition (ED) techniques have been used in the deposition of n-CdS and p-ZnTe layers respectively. Before the fabrication of the one-sided p-n HJ diodes, the electrical properties of glass/FTO/p-ZnTe/Al and glass/FTO/n-CdS/Au rectifying structures were separately studied using capacitance-voltage (C-V) technique so as to determine the doping density of each of the thin films. The results from C-V analyses showed that p-ZnTe is moderately doped with an acceptor density of 3.55 × 1015 cm-3 while n-CdS is heavily doped with a donor density of 9.00 × 1019 cm-3. The heavy doping of n-CdS and moderate doping of p-ZnTe will make the interface between n-CdS and p-ZnTe thin films a one-sided n+p diode. Therefore, to fabricate the CdS/ZnTe hetero-structure, it was ensured that approximately same thickness of CdS and ZnTe thin films being used in the initial experiment to study the electrical properties of glass/FTO/n-CdS/Au and glass/FTO/p-ZnTe/Al were also used in the development of the one-sided n+p junction diodes to obtain more accurate results. The electronic properties of the device structure were studied using both current-voltage (I-V) and C-V measurement techniques. The I-V results show that the one-sided n+p HJ diodes possess good rectifying quality with a series resistance (R s) of ˜35 Ω and rectification factors exceeding 102.7 under dark condition. The results of the C-V analyses showed that the acceptor density of the one-sided n+p HJ diode is of the order of 1015 cm-3 while the donor density is of the order of 1018 cm-3. The results obtained from this analysis still showed the moderate doping of p-ZnTe and the degenerate nature of n-CdS.

  3. Terahertz Nonlinear Optics in Semiconductors

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias C.

    2013-01-01

    We demonstrate the nonlinear optical effects – selfphase modulation and saturable absorption of a single-cycle THz pulse in a semiconductor. Resulting from THz-induced modulation of Drude plasma, these nonlinear optical effects, in particular, lead to self-shortening and nonlinear spectral...

  4. Towards filament free semiconductor lasers

    DEFF Research Database (Denmark)

    McInerney, John; O'Brien, Peter; Skovgaard, Peter M. W.

    2000-01-01

    We outline physical models and simulations for suppression of self-focusing and filamentation in large aperture semiconductor lasers. The principal technical objective is to generate multi-watt CW or quasi-CW outputs with nearly diffraction limited beams, suitable for long distance free space...... propagation structures in lasers and amplifiers which suppress lateral reflections....

  5. Semiconductors for plasmonics and metamaterials

    DEFF Research Database (Denmark)

    Naik, G.V.; Boltasseva, Alexandra

    2010-01-01

    Plasmonics has conventionally been in the realm of metal-optics. However, conventional metals as plasmonic elements in the near-infrared (NIR) and visible spectral ranges suffer from problems such as large losses and incompatibility with semiconductor technology. Replacing metals with semiconduct...

  6. 2010 Defects in Semiconductors GRC

    Energy Technology Data Exchange (ETDEWEB)

    Shengbai Zhang

    2011-01-06

    Continuing its tradition of excellence, this Gordon Conference will focus on research at the forefront of the field of defects in semiconductors. The conference will have a strong emphasis on the control of defects during growth and processing, as well as an emphasis on the development of novel defect detection methods and first-principles defect theories. Electronic, magnetic, and optical properties of bulk, thin film, and nanoscale semiconductors will be discussed in detail. In contrast to many conferences, which tend to focus on specific semiconductors, this conference will deal with point and extended defects in a broad range of electronic materials. This approach has proved to be extremely fruitful for advancing fundamental understanding in emerging materials such as wide-band-gap semiconductors, oxides, sp{sup 2} carbon based-materials, and photovoltaic/solar cell materials, and in understanding important defect phenomena such as doping bottleneck in nanostructures and the diffusion of defects and impurities. The program consists of about twenty invited talks and a number of contributed poster sessions. The emphasis should be on work which has yet to be published. The large amount of discussion time provides an ideal forum for dealing with topics that are new and/or controversial.

  7. Atomistic Models of Amorphous Semiconductors

    NARCIS (Netherlands)

    Jarolimek, K.

    2011-01-01

    Crystalline silicon is probably the best studied material, widely used by the semiconductor industry. The subject of this thesis is an intriguing form of this element namely amorphous silicon. It can contain a varying amount of hydrogen and is denoted as a-Si:H. It completely lacks the neat long

  8. Basic semiconductor physics. 2. ed.

    Energy Technology Data Exchange (ETDEWEB)

    Hamaguchi, Chihiro [Osaka Univ., Suita (Japan). Dept. Electronic Engineering

    2010-07-01

    This book presents a detailed description of the basic semiconductor physics. The reader is assumed to have a basic command of mathematics and some elementary knowledge of solid state physics. The text covers a wide range of important phenomena in semiconductors, from the simple to the advanced. The reader can understand three different methods of energy band calculations, empirical pseudo-potential, k.p perturbation and tight-binding methods. The effective mass approximation and electron motion in a periodic potential, Boltzmann transport equation and deformation potentials used for full band Monte Carlo simulation are discussed. Experiments and theoretical analysis of cyclotron resonance are discussed in detail because the results are essential to the understanding of semiconductor physics. Optical and transport properties, magneto-transport, two dimensional electron gas transport (HEMT and MOSFET), and quantum transport are reviewed, explaining optical transition, electron phonon interactions, electron mobility. Recent progress in quantum structures such as two-dimensional electron gas, superlattices, quantum Hall effect, electron confinement and the Landauer formula are included. The Quantum Hall effect is presented with different models. In the second edition, the addition energy and electronic structure of a quantum dot (artificial atom) are explained with the help of Slater determinants. Also the physics of semiconductor Lasers is described in detail including Einstein coefficients, stimulated emission, spontaneous emission, laser gain, double heterostructures, blue Lasers, optical confinement, laser modes, strained quantum wells lasers which will give insight into the physics of various kinds of semiconductor lasers, in addition to the various processes of luminescence. (orig.)

  9. Semiconductor detectors in nuclear and particle physics

    Energy Technology Data Exchange (ETDEWEB)

    Rehak, P. [Brookhaven National Lab., Upton, NY (United States); Gatti, E. [Piazza Leonardo da Vinci 32, Milano (Italy)

    1992-12-31

    Semiconductor detectors for elementary particle physics and nuclear physics in the energy range above 1 GeV are briefly reviewed. In these two fields semiconductor detectors are used mainly for the precise position sensing. In a typical experiment, the position of a fast charged particle crossing a relatively thin semiconductor detector is measured. The position resolution achievable by semiconductor detectors is compared with the resolution achievable by gas filled position sensing detectors. Semiconductor detectors are divided into two groups: Classical semiconductor diode detectors and semiconductor memory detectors. Principles of the signal formation and the signal read-out for both groups of detectors are described. New developments of silicon detectors of both groups are reported.

  10. Semiconductor detectors in nuclear and particle physics

    Energy Technology Data Exchange (ETDEWEB)

    Rehak, P. [Brookhaven National Laboratory, Upton, New York 11973 (United States); Gatti, E. [Politecnico di Milano, Dipartimento di Elletronica e Informazione, Piazza Leondardo da Vinci 32, 20133 Milano (Italy)

    1995-07-10

    Semiconductor detectors for elementary particle physics and nuclear physics in the energy range above 1 GeV are briefly reviewed. In these two fields semiconductor detectors are used mainly for the precise position sensing. In a typical experiment, the position of a fast charged particle crossing a relatively thin semiconductor detector is measured. The position resolution achievable by semiconductor detectors is compared with the resolution achievable by gas filled position sensing detectors. Semiconductor detectors are divided into two groups; (i) classical semiconductor diode detectors and (ii) semiconductor memory detectors. Principles of the signal formation and the signal read-out for both groups of detectors are described. New developments of silicon detectors of both groups are reported. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  11. Accuracy of dielectric-dependent hybrid functionals in the prediction of optoelectronic properties of metal oxide semiconductors: a comprehensive comparison with many-body GW and experiments

    Science.gov (United States)

    Gerosa, M.; E Bottani, C.; Di Valentin, C.; Onida, G.; Pacchioni, G.

    2018-01-01

    Understanding the electronic structure of metal oxide semiconductors is crucial to their numerous technological applications, such as photoelectrochemical water splitting and solar cells. The needed experimental and theoretical knowledge goes beyond that of pristine bulk crystals, and must include the effects of surfaces and interfaces, as well as those due to the presence of intrinsic defects (e.g. oxygen vacancies), or dopants for band engineering. In this review, we present an account of the recent efforts in predicting and understanding the optoelectronic properties of oxides using ab initio theoretical methods. In particular, we discuss the performance of recently developed dielectric-dependent hybrid functionals, providing a comparison against the results of many-body GW calculations, including G 0 W 0 as well as more refined approaches, such as quasiparticle self-consistent GW. We summarize results in the recent literature for the band gap, the band level alignment at surfaces, and optical transition energies in defective oxides, including wide gap oxide semiconductors and transition metal oxides. Correlated transition metal oxides are also discussed. For each method, we describe successes and drawbacks, emphasizing the challenges faced by the development of improved theoretical approaches. The theoretical section is preceded by a critical overview of the main experimental techniques needed to characterize the optoelectronic properties of semiconductors, including absorption and reflection spectroscopy, photoemission, and scanning tunneling spectroscopy (STS).

  12. Spectroscopic analysis of optoelectronic semiconductors

    CERN Document Server

    Jimenez, Juan

    2016-01-01

    This book deals with standard spectroscopic techniques which can be used to analyze semiconductor samples or devices, in both, bulk, micrometer and submicrometer scale. The book aims helping experimental physicists and engineers to choose the right analytical spectroscopic technique in order to get specific information about their specific demands. For this purpose, the techniques including technical details such as apparatus and probed sample region are described. More important, also the expected outcome from experiments is provided. This involves also the link to theory, that is not subject of this book, and the link to current experimental results in the literature which are presented in a review-like style. Many special spectroscopic techniques are introduced and their relationship to the standard techniques is revealed. Thus the book works also as a type of guide or reference book for people researching in optical spectroscopy of semiconductors.

  13. Catalysts, Protection Layers, and Semiconductors

    DEFF Research Database (Denmark)

    Chorkendorff, Ib

    2015-01-01

    acid or alkaline conditions. Since most relevant semiconductors are very prone to corrosion the advantage of using buried junctions and using protection layers offering shall be discussed [2-4]. Next we shall discuss the availability of various catalysts for being coupled to these protections layers...... and how their stability may be evaluated [5, 6]. Examples of half-cell reaction using protection layers for both cathode and anode will be discussed though some of recent examples under both alkaline and acidic conditions. Si is a very good low band gap semiconductor and by using TiO2 as a protection...... layer we can stabilize it for both H2 and O2 evolution [7, 8, 9, 10]. Notably NiOx promoted by iron is a material that is transparent, providing protection, and is a good catalyst for O2 evolution. We have also recently started searching for large band gap semicondutors like III-V based or pervoskite...

  14. Transversal light forces in semiconductors

    CERN Document Server

    Lindberg, M

    2003-01-01

    The transversal light force is a well established effect in atomic and molecular systems that are exposed to spatially inhomogeneous light fields. In this paper it is shown theoretically that in an excited semiconductor, containing an electron-hole plasma or excitons, a similar light force exists, if the semiconductor is exposed to an ultrashort spatially inhomogeneous light field. The analysis is based on the equations of motion for the Wigner distribution functions of charge carrier populations and interband polarizations. The results show that, while the light force on the electron-hole plasma or the excitons does exist, its effects on the kinetic behaviour of the electron-hole plasma or the excitons are different compared to the situation in an atomic or molecular system. A detailed analysis presented here traces this difference back to the principal differences between atoms and molecules on the one hand and electron-hole plasmas or excitons on the other hand.

  15. Semiconductor electrolyte photovoltaic energy converter

    Science.gov (United States)

    Anderson, W. W.; Anderson, L. B.

    1975-01-01

    Feasibility and practicality of a solar cell consisting of a semiconductor surface in contact with an electrolyte are evaluated. Basic components and processes are detailed for photovoltaic energy conversion at the surface of an n-type semiconductor in contact with an electrolyte which is oxidizing to conduction band electrons. Characteristics of single crystal CdS, GaAs, CdSe, CdTe and thin film CdS in contact with aqueous and methanol based electrolytes are studied and open circuit voltages are measured from Mott-Schottky plots and open circuit photo voltages. Quantum efficiencies for short circuit photo currents of a CdS crystal and a 20 micrometer film are shown together with electrical and photovoltaic properties. Highest photon irradiances are observed with the GaAs cell.

  16. Hypersonic modes in nanophononic semiconductors.

    Science.gov (United States)

    Hepplestone, S P; Srivastava, G P

    2008-09-05

    Frequency gaps and negative group velocities of hypersonic phonon modes in periodically arranged composite semiconductors are presented. Trends and criteria for phononic gaps are discussed using a variety of atomic-level theoretical approaches. From our calculations, the possibility of achieving semiconductor-based one-dimensional phononic structures is established. We present results of the location and size of gaps, as well as negative group velocities of phonon modes in such structures. In addition to reproducing the results of recent measurements of the locations of the band gaps in the nanosized Si/Si{0.4}Ge{0.6} superlattice, we show that such a system is a true one-dimensional hypersonic phononic crystal.

  17. Epitaxial Lateral Overgrowth of Semiconductors

    Science.gov (United States)

    Zytkiewicz, Zbigniew R.

    The state of the art and recent developments of lateral overgrowth of compound semiconductors are reviewed. First we focus on the mechanism of epitaxial lateral overgrowth (ELO) from the liquid phase, highlighting the phenomena that are crucial for growing high-quality layers with large aspect ratio. Epitaxy from the liquid phase has been chosen since the equilibrium growth techniques such as liquid-phase epitaxy (LPE) are the most suitable for lateral overgrowth. We then present numerous examples for which the defect filtration in the ELO procedure is very efficient and leads to significant progress in the development of high-performance semiconductor devices made of lattice-mismatched structures. Structural perfection of seams that appear when layers grown from neighboring seeds merge is also discussed. Next, we concentrate on strain commonly found in various ELO structures and arising due to the interaction of ELO layers with the mask. Its origin, and possible ways of its control, are presented. Then we show that the thermal strain in lattice-mismatched ELO structures can be relaxed by additional tilting of ELO wings while still preserving their high quality. Finally, recent progresses in the lateral overgrowth of semiconductors, including new mask materials and liquid-phase electroepitaxial growth on substrates coated by electrically conductive masks, are presented. New versions of the ELO technique from solution and from the vapor (growth from ridges and pendeo-epitaxy) are described and compared with standard ELO. A wide range of semiconductors, including III-V compounds grown from solution and vapor-grown GaN, are used to illustrate phenomena discussed. Very often, the similar behavior of various ELO structures reveals that the phenomena presented are not related to a specific group of compounds or their growth techniques, but have a much more general nature.

  18. Identification of defects in semiconductors

    CERN Document Server

    Stavola, Michael; Weber, Eicke R; Stavola, Michael

    1998-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors.The"Willardson and Beer"Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices,Oxygen in Silicon, and others promise indeed that this traditi...

  19. Ballistic superconductivity in semiconductor nanowires.

    Science.gov (United States)

    Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K; van Veen, Jasper; de Moor, Michiel W A; Bommer, Jouri D S; van Woerkom, David J; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Quintero-Pérez, Marina; Cassidy, Maja C; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P

    2017-07-06

    Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices.

  20. 75 FR 49526 - Freescale Semiconductor, Inc., Technical Information Center, Tempe, AZ; Freescale Semiconductor...

    Science.gov (United States)

    2010-08-13

    ... Employment and Training Administration Freescale Semiconductor, Inc., Technical Information Center, Tempe, AZ; Freescale Semiconductor, Inc., Technical Information Center, Woburn, MA; Amended Certification Regarding... to Apply for Worker Adjustment Assistance on October 1, 2009, applicable to workers of Freescale...

  1. Electronic properties of semiconductor surfaces and metal/semiconductor interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Tallarida, M.

    2005-05-15

    This thesis reports investigations of the electronic properties of a semiconductor surface (silicon carbide), a reactive metal/semiconductor interface (manganese/silicon) and a non-reactive metal/semiconductor interface (aluminum-magnesium alloy/silicon). The (2 x 1) reconstruction of the 6H-SiC(0001) surface has been obtained by cleaving the sample along the (0001) direction. This reconstruction has not been observed up to now for this compound, and has been compared with those of similar elemental semiconductors of the fourth group of the periodic table. This comparison has been carried out by making use of photoemission spectroscopy, analyzing the core level shifts of both Si 2p and C 1s core levels in terms of charge transfer between atoms of both elements and in different chemical environments. From this comparison, a difference between the reconstruction on the Si-terminated and the C-terminated surface was established, due to the ionic nature of the Si-C bond. The growth of manganese films on Si(111) in the 1-5 ML thickness range has been studied by means of LEED, STM and photoemission spectroscopy. By the complementary use of these surface science techniques, two different phases have been observed for two thickness regimes (<1 ML and >1 ML), which exhibit a different electronic character. The two reconstructions, the (1 x 1)-phase and the ({radical}3 x {radical}3)R30 -phase, are due to silicide formation, as observed in core level spectroscopy. The growth proceeds via island formation in the monolayer regime, while the thicker films show flat layers interrupted by deep holes. On the basis of STM investigations, this growth mode has been attributed to strain due to lattice mismatch between the substrate and the silicide. Co-deposition of Al and Mg onto a Si(111) substrate at low temperature (100K) resulted in the formation of thin alloy films. By varying the relative content of both elements, the thin films exhibited different electronic properties

  2. Emission and Absorption Entropy Generation in Semiconductors

    OpenAIRE

    Reck, Kasper; Varpula, Aapo; Prunnila, Mika; Hansen, Ole

    2013-01-01

    While emission and absorption entropy generation is well known in black bodies, it has not previously been studied in semiconductors, even though semiconductors are widely used for solar light absorption in modern solar cells [1]. We present an analysis of the entropy generation in semiconductor materials due to emission and absorption of electromagnetic radiation. It is shown that the emission and absorption entropy generation reduces the fundamental limit on the efficiency of any semiconduc...

  3. Hybridization at superconductor-semiconductor interfaces

    OpenAIRE

    Mikkelsen, August E. G.; Kotetes, Panagiotis; Krogstrup, Peter; Flensberg, Karsten

    2018-01-01

    Hybrid superconductor-semiconductor devices are currently one of the most promising platforms for realizing Majorana zero modes. We address the role of band bending and superconductor-semiconductor hybridization in such devices by analyzing a gated single Al-InAs interface using a self-consistent Schroedinger-Poisson approach. Our numerical analysis shows that the band bending leads to an interface quantum well, which localizes the charge in the system near the superconductor-semiconductor in...

  4. Semiconductor power devices physics, characteristics, reliability

    CERN Document Server

    Lutz, Josef; Scheuermann, Uwe; De Doncker, Rik

    2011-01-01

    Semiconductor power devices are the heart of power electronics. They determine the performance of power converters and allow topologies with high efficiency. Semiconductor properties, pn-junctions and the physical phenomena for understanding power devices are discussed in depth. Working principles of state-of-the-art power diodes, thyristors, MOSFETs and IGBTs are explained in detail, as well as key aspects of semiconductor device production technology. In practice, not only the semiconductor, but also the thermal and mechanical properties of packaging and interconnection technologies are esse

  5. Toward a national semiconductor strategy, volume 1

    Science.gov (United States)

    1991-02-01

    Updated here are key market data showing trends in the U.S. semiconductor industry's world market position. New information is given on three emerging semiconductor-based technologies: broadband communications, advanced display systems, and intelligent vehicles and highways. These are examples of important, high-volume markets that will consume significant numbers of semiconductor components and that must be addressed in a national semiconductor strategy. New recommendations and a summary of all Committee recommendations to date are given as well as a summary of comments received at a public forum held in Silicon Valley in may 1990.

  6. Microradiography with Semiconductor Pixel Detectors

    Science.gov (United States)

    Jakubek, Jan; Cejnarova, Andrea; Dammer, Jiří; Holý, Tomáš; Platkevič, Michal; Pospíšil, Stanislav; Vavřík, Daniel; Vykydal, Zdeněk

    2007-11-01

    High resolution radiography (with X-rays, neutrons, heavy charged particles, …) often exploited also in tomographic mode to provide 3D images stands as a powerful imaging technique for instant and nondestructive visualization of fine internal structure of objects. Novel types of semiconductor single particle counting pixel detectors offer many advantages for radiation imaging: high detection efficiency, energy discrimination or direct energy measurement, noiseless digital integration (counting), high frame rate and virtually unlimited dynamic range. This article shows the application and potential of pixel detectors (such as Medipix2 or TimePix) in different fields of radiation imaging.

  7. Optoelectronic properties of semiconductor nanostructures

    Science.gov (United States)

    Maher, Kristin Nicole

    Semiconductor nanostructures have unique optical and electronic properties that have inspired research into their technological applications and basic science. This thesis presents approaches to the fabrication and characterization of optoelectronic devices incorporating individual semiconductor nanostructures. Nanowires of the II-VI semiconductors CdSe and CdS were synthesized using nanoparticle-catalysed solution-liquid-solid growth. Single-component nanowires and heterostructure nanowires with axial compositional modulation were generated using this method. Individual nanowires and nanocrystals were then incorporated into devices with a three-terminal field-effect transistor geometry. An experimental platform was developed which allows for simultaneous electrical characterization of devices and measurement of their optical properties. This setup enables the measurement of spatially and spectrally resolved electroluminescence (EL) and photoluminescence (PL) from individual nanostructures and nanostructure devices. It also allows the measurement of photon coincidence histograms for emitted light and the acquisition of photocurrent images via laser scanning microscopy. Electroluminescence was observed from individual CdSe nanocrystals contacted by gold electrodes. Concomitant transport measurements at low temperature showed clear evidence of Coulomb blockade at low bias voltage, with light only emitted from devices exhibiting asymmetric tunnel couplings between the nanocrystal and electrodes. Combined analyses of the data indicate that the resistances of the tunnel barriers are bias voltage dependent and that light emission results from the inelastic scattering of tunneling electrons. Three-terminal devices incorporating individual CdSe nanoNvires exhibited EL localized near the positively-biased electrode. Characterization of these devices by scanning photocurrent microscopy (SPCM) and Kelvin probe microscopy (KPM) indicates that while there are n-type Schottky

  8. Optic probe for semiconductor characterization

    Science.gov (United States)

    Sopori, Bhushan L [Denver, CO; Hambarian, Artak [Yerevan, AM

    2008-09-02

    Described herein is an optical probe (120) for use in characterizing surface defects in wafers, such as semiconductor wafers. The optical probe (120) detects laser light reflected from the surface (124) of the wafer (106) within various ranges of angles. Characteristics of defects in the surface (124) of the wafer (106) are determined based on the amount of reflected laser light detected in each of the ranges of angles. Additionally, a wafer characterization system (100) is described that includes the described optical probe (120).

  9. Trace analysis of semiconductor materials

    CERN Document Server

    Cali, J Paul; Gordon, L

    1964-01-01

    Trace Analysis of Semiconductor Materials is a guidebook concerned with procedures of ultra-trace analysis. This book discusses six distinct techniques of trace analysis. These techniques are the most common and can be applied to various problems compared to other methods. Each of the four chapters basically includes an introduction to the principles and general statements. The theoretical basis for the technique involved is then briefly discussed. Practical applications of the techniques and the different instrumentations are explained. Then, the applications to trace analysis as pertaining

  10. Electronic Properties of Semiconductor Interfaces.

    Science.gov (United States)

    1983-02-01

    AD-A130 745 ELECTRONIC PROPERTIES OF SEMICONDUCTOR INTERFACES(U) /; UNIVERSIDAD AUfONOMA DE MADRID (SPAIN) DEPT DE FISICA DEL ESTADO SOLIDO F FLORES...Estado Solido 6.11.02A Universidad Autonoma Cantoblanco, Madrid 34. Spain 1T161102BH57-03 11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE...different supe4layeru formed by the superlayers (0,1), (2,3), (4,5),... and so on. Note that the number of super - layers defined inside each 6upettayer

  11. Processing of insulators and semiconductors

    Science.gov (United States)

    Quick, Nathaniel R.; Joshi, Pooran C.; Duty, Chad Edward; Jellison, Jr., Gerald Earle; Angelini, Joseph Attilio

    2015-06-16

    A method is disclosed for processing an insulator material or a semiconductor material. The method includes pulsing a plasma lamp onto the material to diffuse a doping substance into the material, to activate the doping substance in the material or to metallize a large area region of the material. The method may further include pulsing a laser onto a selected region of the material to diffuse a doping substance into the material, to activate the doping substance in the material or to metallize a selected region of the material.

  12. Semiconductor-Based Nanotechnology Applications

    Science.gov (United States)

    2012-11-07

    as SnO2 , ZnO, and CeO2, reported in 40 refereed research papers. In this ARO project, studies on ultra small particles of these oxides with...semiconductors such as SnO2 , ZnO, and CeO2, reported in 40 refereed research papers. In this ARO project, studies on ultra small particles of these oxides...ferromagnetism. Thin film structures using Co doped SnO2 were fabricated and studied their usefulness in device applications. NP of semiconducting oxides such

  13. Dual modulation of semiconductor lasers

    Energy Technology Data Exchange (ETDEWEB)

    Gorfinkel, V.B. [Univ. of Kassel (Germany); Luryi, S. [AT and T Bell Labs., Murray Hill, NJ (United States)

    1994-12-31

    Large signal analysis of dual modulation of semiconductor lasers (by a simultaneous high-frequency control of the pumping current I and an additional intrinsic parameter) shows that the method allows suppressing the relaxation oscillations for an arbitrary shape of the pumping current signal I (t). Because of that, the rate of information coding can be enhanced to about 80 Gbit/sec. Moreover, the authors demonstrate that dual modulation allows to maintain a linear relationship between I (t) and the output optical power in a wide frequency band.

  14. Suitability of integrated protection diodes from diverse semiconductor technologies

    NARCIS (Netherlands)

    van Wanum, Maurice; Lebouille, Tom; Visser, Guido; van Vliet, Frank Edward

    2009-01-01

    Abstract In this article diodes from three different semiconductor technologies are compared based on their suitability to protect a receiver. The semiconductor materials involved are silicon, gallium arsenide and gallium nitride. The diodes in the diverse semiconductor technologies themselves are

  15. Semiconductor nanostructures for artificial photosynthesis

    Science.gov (United States)

    Yang, Peidong

    2012-02-01

    Nanowires, with their unique capability to bridge the nanoscopic and macroscopic worlds, have already been demonstrated as important materials for different energy conversion. One emerging and exciting direction is their application for solar to fuel conversion. The generation of fuels by the direct conversion of solar energy in a fully integrated system is an attractive goal, but no such system has been demonstrated that shows the required efficiency, is sufficiently durable, or can be manufactured at reasonable cost. One of the most critical issues in solar water splitting is the development of a suitable photoanode with high efficiency and long-term durability in an aqueous environment. Semiconductor nanowires represent an important class of nanostructure building block for direct solar-to-fuel application because of their high surface area, tunable bandgap and efficient charge transport and collection. Nanowires can be readily designed and synthesized to deterministically incorporate heterojunctions with improved light absorption, charge separation and vectorial transport. Meanwhile, it is also possible to selectively decorate different oxidation or reduction catalysts onto specific segments of the nanowires to mimic the compartmentalized reactions in natural photosynthesis. In this talk, I will highlight several recent examples in this lab using semiconductor nanowires and their heterostructures for the purpose of direct solar water splitting.

  16. Semiconductor X-ray detectors

    CERN Document Server

    Lowe, Barrie Glyn

    2014-01-01

    Identifying and measuring the elemental x-rays released when materials are examined with particles (electrons, protons, alpha particles, etc.) or photons (x-rays and gamma rays) is still considered to be the primary analytical technique for routine and non-destructive materials analysis. The Lithium Drifted Silicon (Si(Li)) X-Ray Detector, with its good resolution and peak to background, pioneered this type of analysis on electron microscopes, x-ray fluorescence instruments, and radioactive source- and accelerator-based excitation systems. Although rapid progress in Silicon Drift Detectors (SDDs), Charge Coupled Devices (CCDs), and Compound Semiconductor Detectors, including renewed interest in alternative materials such as CdZnTe and diamond, has made the Si(Li) X-Ray Detector nearly obsolete, the device serves as a useful benchmark and still is used in special instances where its large, sensitive depth is essential. Semiconductor X-Ray Detectors focuses on the history and development of Si(Li) X-Ray Detect...

  17. Terahertz semiconductor-heterostructure laser.

    Science.gov (United States)

    Köhler, Rüdeger; Tredicucci, Alessandro; Beltram, Fabio; Beere, Harvey E; Linfield, Edmund H; Davies, A Giles; Ritchie, David A; Iotti, Rita C; Rossi, Fausto

    2002-05-09

    Semiconductor devices have become indispensable for generating electromagnetic radiation in everyday applications. Visible and infrared diode lasers are at the core of information technology, and at the other end of the spectrum, microwave and radio-frequency emitters enable wireless communications. But the terahertz region (1-10 THz; 1 THz = 10(12) Hz) between these ranges has remained largely underdeveloped, despite the identification of various possible applications--for example, chemical detection, astronomy and medical imaging. Progress in this area has been hampered by the lack of compact, low-consumption, solid-state terahertz sources. Here we report a monolithic terahertz injection laser that is based on interminiband transitions in the conduction band of a semiconductor (GaAs/AlGaAs) heterostructure. The prototype demonstrated emits a single mode at 4.4 THz, and already shows high output powers of more than 2 mW with low threshold current densities of about a few hundred A cm(-2) up to 50 K. These results are very promising for extending the present laser concept to continuous-wave and high-temperature operation, which would lead to implementation in practical photonic systems.

  18. Modeling of semiconductor nanostructures and semiconductor-electrolyte interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Birner, Stefan

    2011-11-15

    The main objective of Part I is to give an overview of some of the methods that have been implemented into the nextnano{sup 3} software. Examples are discussed that give insight into doping, strain and mobility. Applications of the single-band Schroedinger equation include three-dimensional superlattices, and a qubit that is manipulated by a magnetic field. Results of the multi-band k.p method are presented for HgTe-CdTe and InAs-GaSb superlattices, and for a SiGe-Si quantum cascade structure. Particular focus is put on a detailed description of the contact block reduction (CBR) method that has been developed within our research group. By means of this approach, quantum transport in the ballistic limit in one, two and three dimensions can be calculated. I provide a very detailed description of the algorithm and present several well documented examples that highlight the key points of this method. Calculating quantum transport in three dimensions is a very challenging task where computationally efficient algorithms - apart from the CBR method - are not available yet. Part II describes the methods that I have implemented into the nextnano{sup 3} software for calculating systems that consist of a combination of semiconductor materials and liquids. These biosensors have a solid-electrolyte interface, and the charges in the solid and in the electrolyte are coupled to each other through the Poisson-Boltzmann equation. I apply this model to a silicon based protein sensor, where I solve the Schroedinger equation together with the Poisson-Boltzmann equation self-consistently, and compare theoretical results with experiment. Furthermore, I have developed a novel approach to model the charge density profiles at semiconductor-electrolyte interfaces that allows us to distinguish hydrophobic and hydrophilic interfaces. Our approach extends previous work where ion specific potentials of mean force describe the distribution of ion species at the interface. I apply this new model

  19. Novel room temperature ferromagnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Amita [KTH Royal Inst. of Technology, Stockholm (Sweden)

    2004-06-01

    Today's information world, bits of data are processed by semiconductor chips, and stored in the magnetic disk drives. But tomorrow's information technology may see magnetism (spin) and semiconductivity (charge) combined in one 'spintronic' device that exploits both charge and 'spin' to carry data (the best of two worlds). Spintronic devices such as spin valve transistors, spin light emitting diodes, non-volatile memory, logic devices, optical isolators and ultra-fast optical switches are some of the areas of interest for introducing the ferromagnetic properties at room temperature in a semiconductor to make it multifunctional. The potential advantages of such spintronic devices will be higher speed, greater efficiency, and better stability at a reduced power consumption. This Thesis contains two main topics: In-depth understanding of magnetism in Mn doped ZnO, and our search and identification of at least six new above room temperature ferromagnetic semiconductors. Both complex doped ZnO based new materials, as well as a number of nonoxides like phosphides, and sulfides suitably doped with Mn or Cu are shown to give rise to ferromagnetism above room temperature. Some of the highlights of this work are discovery of room temperature ferromagnetism in: (1) ZnO:Mn (paper in Nature Materials, Oct issue, 2003); (2) ZnO doped with Cu (containing no magnetic elements in it); (3) GaP doped with Cu (again containing no magnetic elements in it); (4) Enhancement of Magnetization by Cu co-doping in ZnO:Mn; (5) CdS doped with Mn, and a few others not reported in this thesis. We discuss in detail the first observation of ferromagnetism above room temperature in the form of powder, bulk pellets, in 2-3 mu-m thick transparent pulsed laser deposited films of the Mn (<4 at. percent) doped ZnO. High-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) spectra recorded from 2 to 200nm areas showed homogeneous

  20. New semiconductor materials for magnetoelectronics at room ...

    Indian Academy of Sciences (India)

    Most of the semiconductor materials are diamagnetic by nature and therefore cannot take active part in the operation of the magneto electronic devices. In order to enable them to be useful for such devices a recent effort has been made to develop diluted magnetic semiconductors (DMS) in which small quantity of magnetic ...

  1. Epitaxy of semiconductor-superconductor nanowires

    DEFF Research Database (Denmark)

    Krogstrup, P.; Ziino, N.L.B.; Chang, W.

    2015-01-01

    Controlling the properties of semiconductor/metal interfaces is a powerful method for designing functionality and improving the performance of electrical devices. Recently semiconductor/superconductor hybrids have appeared as an important example where the atomic scale uniformity of the interface...

  2. Semiconductor saturable absorbers for ultrafast terahertz signals

    DEFF Research Database (Denmark)

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    2010-01-01

    We demonstrate saturable absorber behavior of n-type semiconductors GaAs, GaP, and Ge in the terahertz THz frequency range at room temperature using nonlinear THz spectroscopy. The saturation mechanism is based on a decrease in electron conductivity of semiconductors at high electron momentum...

  3. Semiconductor composition containing iron, dysprosium, and terbium

    Energy Technology Data Exchange (ETDEWEB)

    Pooser, Raphael C.; Lawrie, Benjamin J.; Baddorf, Arthur P.; Malasi, Abhinav; Taz, Humaira; Farah, Annettee E.; Kalyanaraman, Ramakrishnan; Duscher, Gerd Josef Mansfred; Patel, Maulik K.

    2017-09-26

    An amorphous semiconductor composition includes 1 to 70 atomic percent iron, 15 to 65 atomic percent dysprosium, 15 to 35 atomic percent terbium, balance X, wherein X is at least one of an oxidizing element and a reducing element. The composition has an essentially amorphous microstructure, an optical transmittance of at least 50% in at least the visible spectrum and semiconductor electrical properties.

  4. Packaging of high power semiconductor lasers

    CERN Document Server

    Liu, Xingsheng; Xiong, Lingling; Liu, Hui

    2014-01-01

    This book introduces high power semiconductor laser packaging design. The characteristics and challenges of the design and various packaging, processing, and testing techniques are detailed by the authors. New technologies, in particular thermal technologies, current applications, and trends in high power semiconductor laser packaging are described at length and assessed.

  5. neutron-Induced Failures in semiconductor Devices

    Energy Technology Data Exchange (ETDEWEB)

    Wender, Stephen Arthur [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-13

    Single Event Effects are a very significant failure mode in modern semiconductor devices that may limit their reliability. Accelerated testing is important for semiconductor industry. Considerable more work is needed in this field to mitigate the problem. Mitigation of this problem will probably come from Physicists and Electrical Engineers working together

  6. Molecular semiconductors photoelectrical properties and solar cells

    CERN Document Server

    Rees, Ch

    1985-01-01

    During the past thirty years considerable efforts have been made to design the synthesis and the study of molecular semiconductors. Molecular semiconductors - and more generally molecular materials - involve interactions between individual subunits which can be separately synthesized. Organic and metallo-organic derivatives are the basis of most of the molecular materials. A survey of the literature on molecular semiconductors leaves one rather confused. It does seem to be very difficult to correlate the molecular structure of these semiconductors with their experimental electrical properties. For inorganic materials a simple definition delimits a fairly homogeneous family. If an inorganic material has a conductivity intermediate between that of an 12 1 1 3 1 1 insulator « 10- n- cm- ) and that of a metal (> 10 n- cm- ), then it is a semiconductor and will exhibit the characteristic properties of this family, such as junction formation, photoconductivity, and the photovoltaic effect. For molecular compounds,...

  7. Physics of semiconductor devices (2nd edition)

    Energy Technology Data Exchange (ETDEWEB)

    Sze, S.M.

    1981-01-01

    A resume is presented regarding the physics and properties of semiconductors, taking into account aspects of crystal structure, the energy bands, the carrier concentration at thermal equilibrium, carrier transport phenomena, basic equations for semiconductor device operation, and phonon spectra and optical, thermal, and high-field properties of semiconductors. The bipolar devices considered include the p-n junction diode, the bipolar transistor, and thyristors. Unipolar devices are discussed, taking into account metal-semiconductor contacts, JFET and MESFET, the MIS diode and CCD, and MOSFET. A description is provided of special microwave devices, giving attention to tunnel devices, IMPATT and related transit-time diodes, and transferred-electron devices. Photonic devices investigated include LED and semiconductor lasers, photodetectors, and solar cells.

  8. Device Physics of Narrow Gap Semiconductors

    CERN Document Server

    Chu, Junhao

    2010-01-01

    Narrow gap semiconductors obey the general rules of semiconductor science, but often exhibit extreme features of these rules because of the same properties that produce their narrow gaps. Consequently these materials provide sensitive tests of theory, and the opportunity for the design of innovative devices. Narrow gap semiconductors are the most important materials for the preparation of advanced modern infrared systems. Device Physics of Narrow Gap Semiconductors offers descriptions of the materials science and device physics of these unique materials. Topics covered include impurities and defects, recombination mechanisms, surface and interface properties, and the properties of low dimensional systems for infrared applications. This book will help readers to understand not only the semiconductor physics and materials science, but also how they relate to advanced opto-electronic devices. The last chapter applies the understanding of device physics to photoconductive detectors, photovoltaic infrared detector...

  9. Manipulating semiconductor colloidal stability through doping.

    Science.gov (United States)

    Fleharty, Mark E; van Swol, Frank; Petsev, Dimiter N

    2014-10-10

    The interface between a doped semiconductor material and electrolyte solution is of considerable fundamental interest, and is relevant to systems of practical importance. Both adjacent domains contain mobile charges, which respond to potential variations. This is exploited to design electronic and optoelectronic sensors, and other enabling semiconductor colloidal materials. We show that the charge mobility in both phases leads to a new type of interaction between semiconductor colloids suspended in aqueous electrolyte solutions. This interaction is due to the electrostatic response of the semiconductor interior to disturbances in the external field upon the approach of two particles. The electrostatic repulsion between two charged colloids is reduced from the one governed by the charged groups present at the particles surfaces. This type of interaction is unique to semiconductor particles and may have a substantial effect on the suspension dynamics and stability.

  10. Electrons in metals and semiconductors

    CERN Document Server

    Chambers, R G

    1990-01-01

    This book is part of a series of short texts for students, scientists and engineers who seek to broaden their knowledge of the physics underlying modern technology. This text aims to provide a review of the fundamental physics and recent developments in the area of solid-state physics. The book contains a range of topics discussing metals and semiconductors with references to treatises and the primary literature to facilitate further study. The book is intended to be useful to those engaged in research and development, who require a summary of a topic in physics or a new application of physical principles in their work. Many of the the texts will also be useful for final year undergraduate and postgraduate students.

  11. Semirelativity in semiconductors: a review

    Science.gov (United States)

    Zawadzki, Wlodek

    2017-09-01

    An analogy between behavior of electrons in narrow-gap semiconductors (NGS) and relativistic electrons in vacuum is reviewed. Energy band structures \\varepsilon ≤ft(\\mathbf{k}\\right) are considered for various NGS materials and their correspondence to the energy-momentum relation in special relativity is emphasized. It is indicated that special relativity for vacuum is analogous to a two-band \\mathbf{k}\\centerdot \\mathbf{p} description for NGS. The maximum electron velocity in NGS is u≃ 1× {{10}8}~\\text{cm}~{{\\text{s}}-1} , which corresponds to the light velocity in vacuum. An effective mass of charge carriers in semiconductors is introduced, relating their velocity to quasimomentum and it is shown that this mass depends on electron energy (or velocity) in a way similar to the mass of free relativistic electrons. In \\text{H}{{\\text{g}}1-x}\\text{C}{{\\text{d}}x}\\text{Te} alloys one can reach vanishing energy gap at which electrons and light holes become three-dimensional massless Dirac fermions. A wavelength {λz} is defined for NGS, in analogy to the Compton wavelength in relativistic quantum mechanics. It is estimated that {λz} is on the order of tens of Angstroms in typical semiconducting materials which is experimentally confirmed in tunneling experiments on energy dispersion in the forbidden gap. Statistical properties of the electron gas in NGS are calculated and their similarity is demonstrated to those of the Juttner gas of relativistic particles. Interband electron tunneling in NGS is described and shown to be in close analogy to the predicted but unobserved tunneling between negative and positive energies resulting from the Dirac equation for free electrons. It is demonstrated that the relativistic analogy holds for orbital and spin properties of electrons in the presence of an external magnetic field. In particular, it is shown that the spin magnetic moment of both NGS electrons and relativistic electrons approaches zero with increasing

  12. High throughput semiconductor deposition system

    Energy Technology Data Exchange (ETDEWEB)

    Young, David L.; Ptak, Aaron Joseph; Kuech, Thomas F.; Schulte, Kevin; Simon, John D.

    2017-11-21

    A reactor for growing or depositing semiconductor films or devices. The reactor may be designed for inline production of III-V materials grown by hydride vapor phase epitaxy (HVPE). The operating principles of the HVPE reactor can be used to provide a completely or partially inline reactor for many different materials. An exemplary design of the reactor is shown in the attached drawings. In some instances, all or many of the pieces of the reactor formed of quartz, such as welded quartz tubing, while other reactors are made from metal with appropriate corrosion resistant coatings such as quartz or other materials, e.g., corrosion resistant material, or stainless steel tubing or pipes may be used with a corrosion resistant material useful with HVPE-type reactants and gases. Using HVPE in the reactor allows use of lower-cost precursors at higher deposition rates such as in the range of 1 to 5 .mu.m/minute.

  13. Fundamentals of semiconductor processing technology

    CERN Document Server

    El-Kareh, Badih

    1995-01-01

    The drive toward new semiconductor technologies is intricately related to market demands for cheaper, smaller, faster, and more reliable circuits with lower power consumption. The development of new processing tools and technologies is aimed at optimizing one or more of these requirements. This goal can, however, only be achieved by a concerted effort between scientists, engineers, technicians, and operators in research, development, and manufac­ turing. It is therefore important that experts in specific disciplines, such as device and circuit design, understand the principle, capabil­ ities, and limitations of tools and processing technologies. It is also important that those working on specific unit processes, such as lithography or hot processes, be familiar with other unit processes used to manufacture the product. Several excellent books have been published on the subject of process technologies. These texts, however, cover subjects in too much detail, or do not cover topics important to modem tech­ n...

  14. Theory of Defects in Semiconductors

    CERN Document Server

    Drabold, David A

    2007-01-01

    Semiconductor science and technology is the art of defect engineering. The theoretical modeling of defects has improved dramatically over the past decade. These tools are now applied to a wide range of materials issues: quantum dots, buckyballs, spintronics, interfaces, amorphous systems, and many others. This volume presents a coherent and detailed description of the field, and brings together leaders in theoretical research. Today's state-of-the-art, as well as tomorrow’s tools, are discussed: the supercell-pseudopotential method, the GW formalism,Quantum Monte Carlo, learn-on-the-fly molecular dynamics, finite-temperature treatments, etc. A wealth of applications are included, from point defects to wafer bonding or the propagation of dislocation.

  15. Light-matter interactions in semiconductor nanowires: Light-effect transistor and light-induced changes in electron-phonon coupling and electrical characteristics

    Science.gov (United States)

    Marmon, Jason Kendrick

    is particularly important for electronic transport properties at the nanoscale, where controversy and even contradictory experimental and theoretical findings still persist. Zinc telluride (ZnTe) has important uses in optical or laser refrigeration, and the existing studies do not consider extrinsic effects, such as laser-forming tellurium-based species. Nanostructures, with their large surface-to-volume ratios, are more susceptible to extrinsic perturbations that ultimately effect coupling. In this dissertation, ZnTe is studied in bulk, thin film, and nanowire forms with primary focus on the latter. Raman spectroscopy under near resonant excitation is used to extract electron-phonon coupling strengths, which is obtained through the ratio of the first and second order Raman peaks, R = I2LO/I1LO (and is proportional to the Huang-Rhys factor). Laser-formation of tellurium-based species on ZnTe nanowires dynamically altered the ratio R from 6-7 to 2.4 after laser processing, while tuning the (532 nm) laser power from a few microwatts to 150 microwatts (with constant optical exposure time) did not significantly impact the EPC strength. Other explored effects include size dependence, chemical effects (methanol exposure), and interface effects (e.g., at a gold-nanowire junction). The findings suggest that the previously reported size dependence in ZnTe was extrinsic in nature. Tunable coupling strengths also suggest the possibility of novel electronic and optoelectronic devices. The electrical characteristic of CdSe nanowire M-S-M devices are shown to be tunable with laser illumination. As with any semiconductor material, sufficiently low optical powers produce stable and reproducible electrical properties, while higher optical powers and exposure times can induce laser modifications of the material. Drastic modification of electrical characteristics were observed, such as from converting an ohmic response (linear slope change) to rectified characteristics, and

  16. Diluted magnetic semiconductor nanowires exhibiting magnetoresistance

    Science.gov (United States)

    Yang, Peidong [El Cerrito, CA; Choi, Heonjin [Seoul, KR; Lee, Sangkwon [Daejeon, KR; He, Rongrui [Albany, CA; Zhang, Yanfeng [El Cerrito, CA; Kuykendal, Tevye [Berkeley, CA; Pauzauskie, Peter [Berkeley, CA

    2011-08-23

    A method for is disclosed for fabricating diluted magnetic semiconductor (DMS) nanowires by providing a catalyst-coated substrate and subjecting at least a portion of the substrate to a semiconductor, and dopant via chloride-based vapor transport to synthesize the nanowires. Using this novel chloride-based chemical vapor transport process, single crystalline diluted magnetic semiconductor nanowires Ga.sub.1-xMn.sub.xN (x=0.07) were synthesized. The nanowires, which have diameters of .about.10 nm to 100 nm and lengths of up to tens of micrometers, show ferromagnetism with Curie temperature above room temperature, and magnetoresistance up to 250 Kelvin.

  17. Semiconductor Nanostructures Quantum States and Electronic Transport

    CERN Document Server

    Ihn, Thomas

    2009-01-01

    This textbook describes the physics of semiconductor nanostructures with emphasis on their electronic transport properties. At its heart are five fundamental transport phenomena: quantized conductance, tunnelling transport, the Aharonov-Bohm effect, the quantum Hall effect, and the Coulomb blockade effect. The book starts out with the basics of solid state and semiconductor physics, such as crystal structure, band structure, and effective mass approximation, including spin-orbit interaction effects important for research in semiconductor spintronics. It contains material aspects such as band e

  18. Controlling the stoichiometry and doping of semiconductor materials

    Science.gov (United States)

    Albin, David; Burst, James; Metzger, Wyatt; Duenow, Joel; Farrell, Stuart; Colegrove, Eric

    2016-08-16

    Methods for treating a semiconductor material are provided. According to an aspect of the invention, the method includes annealing the semiconductor material in the presence of a compound that includes a first element and a second element. The first element provides an overpressure to achieve a desired stoichiometry of the semiconductor material, and the second element provides a dopant to the semiconductor material.

  19. Life-cycle assessment of semiconductors

    CERN Document Server

    Boyd, Sarah B

    2012-01-01

    Life-Cycle Assessment of Semiconductors presents the first and thus far only available transparent and complete life cycle assessment of semiconductor devices. A lack of reliable semiconductor LCA data has been a major challenge to evaluation of the potential environmental benefits of information technologies (IT). The analysis and results presented in this book will allow a higher degree of confidence and certainty in decisions concerning the use of IT in efforts to reduce climate change and other environmental effects. Coverage includes but is not limited to semiconductor manufacturing trends by product type and geography, unique coverage of life-cycle assessment, with a focus on uncertainty and sensitivity analysis of energy and global warming missions for CMOS logic devices, life cycle assessment of flash memory and life cycle assessment of DRAM. The information and conclusions discussed here will be highly relevant and useful to individuals and institutions. The book also: Provides a detailed, complete a...

  20. X-ray absorption spectroscopy of semiconductors

    CERN Document Server

    Ridgway, Mark

    2015-01-01

    X-ray Absorption Spectroscopy (XAS) is a powerful technique with which to probe the properties of matter, equally applicable to the solid, liquid and gas phases. Semiconductors are arguably our most technologically-relevant group of materials given they form the basis of the electronic and photonic devices that now so widely permeate almost every aspect of our society. The most effective utilisation of these materials today and tomorrow necessitates a detailed knowledge of their structural and vibrational properties. Through a series of comprehensive reviews, this book demonstrates the versatility of XAS for semiconductor materials analysis and presents important research activities in this ever growing field. A short introduction of the technique, aimed primarily at XAS newcomers, is followed by twenty independent chapters dedicated to distinct groups of materials. Topics span dopants in crystalline semiconductors and disorder in amorphous semiconductors to alloys and nanometric material as well as in-sit...

  1. Analysis and simulation of semiconductor devices

    CERN Document Server

    Selberherr, Siegfried

    1984-01-01

    The invention of semiconductor devices is a fairly recent one, considering classical time scales in human life. The bipolar transistor was announced in 1947, and the MOS transistor, in a practically usable manner, was demonstrated in 1960. From these beginnings the semiconductor device field has grown rapidly. The first integrated circuits, which contained just a few devices, became commercially available in the early 1960s. Immediately thereafter an evolution has taken place so that today, less than 25 years later, the manufacture of integrated circuits with over 400.000 devices per single chip is possible. Coincident with the growth in semiconductor device development, the literature concerning semiconductor device and technology issues has literally exploded. In the last decade about 50.000 papers have been published on these subjects. The advent of so called Very-Large-Scale-Integration (VLSI) has certainly revealed the need for a better understanding of basic device behavior. The miniaturization of the s...

  2. High throughput combinatorial screening of semiconductor materials

    Science.gov (United States)

    Mao, Samuel S.

    2011-11-01

    This article provides an overview of an advanced combinatorial material discovery platform developed recently for screening semiconductor materials with properties that may have applications ranging from radiation detectors to solar cells. Semiconductor thin-film libraries, each consisting of 256 materials of different composition arranged into a 16×16 matrix, were fabricated using laser-assisted evaporation process along with a combinatorial mechanism to achieve variations. The composition and microstructure of individual materials on each thin-film library were characterized with an integrated scanning micro-beam x-ray fluorescence and diffraction system, while the band gaps were determined by scanning optical reflection and transmission of the libraries. An ultrafast ultraviolet photon-induced charge probe was devised to measure the mobility and lifetime of individual thin-film materials on semiconductor libraries. Selected results on the discovery of semiconductors with desired band gaps and transport properties are illustrated.

  3. Semiconductor spintronics - Spins go their own way

    NARCIS (Netherlands)

    van Wees, Bart

    A semiconductor device that integrates electron spin injection, transport, modulation and detection in a single structure provides an important step in versatility for both fundamental research and practical spintronic applications.

  4. Plasmonic effects in metal-semiconductor nanostructures

    CERN Document Server

    Toropov, Alexey A

    2015-01-01

    Metal-semiconductor nanostructures represent an important new class of materials employed in designing advanced optoelectronic and nanophotonic devices, such as plasmonic nanolasers, plasmon-enhanced light-emitting diodes and solar cells, plasmonic emitters of single photons, and quantum devices operating in infrared and terahertz domains. The combination of surface plasmon resonances in conducting structures, providing strong concentration of an electromagnetic optical field nearby, with sharp optical resonances in semiconductors, which are highly sensitive to external electromagnetic fields, creates a platform to control light on the nanoscale. The design of the composite metal-semiconductor system imposes the consideration of both the plasmonic resonances in metal and the optical transitions in semiconductors - a key issue being their resonant interaction providing a coupling regime. In this book the reader will find descriptions of electrodynamics of conducting structures, quantum physics of semiconducto...

  5. Artificial Photosynthesis with Semiconductor-Liquid Junctions

    National Research Council Canada - National Science Library

    Guijarro, Néstor; Formal, Florian Le; Sivula, Kevin

    2015-01-01

    .... solar fuel engineering. In this review we give an overview of the field of artificial photosynthesis using a semiconductor-electrolyte interface employed in a photoelectrochemical device or as a heterogeneous photocatalyst...

  6. Photocatalytic semiconductors synthesis, characterization, and environmental applications

    CERN Document Server

    Hernández-Ramírez, Aracely

    2014-01-01

    This critical volume examines the different methods used for the synthesis of a great number of photocatalysts, including TiO2, ZnO and other modified semiconductors, as well as characterization techniques used for determining the optical, structural and morphological properties of the semiconducting materials. Additionally, the authors discuss photoelectrochemical methods for determining the light activity of the photocatalytic semiconductors by means of measurement of properties such as band gap energy, flat band potential and kinetics of hole and electron transfer. Photocatalytic Semiconductors: Synthesis, Characterization and Environmental Applications provide an overview of the semiconductor materials from first- to third-generation photocatalysts and their applications in wastewater treatment and water disinfection. The book further presents economic and toxicological aspects in the production and application of photocatalytic materials.

  7. Photo-induced strain imaging of semiconductors

    Directory of Open Access Journals (Sweden)

    Keiji Takata

    2017-04-01

    Full Text Available This paper presents a novel method for high-resolutions imaging of band-gap energies of semiconductors. When electron-hole pairs are generated in a semiconductor irradiated with a laser, they induce electronic strains in the semiconductor. The electronic strains can be detected and imaged by a scanning probe microscope. The electron-hole-pair generation depends on the band-gap and photon energies. When there are variations in band-gap energies in a sample, strains could be detected in regions having narrower gaps than the irradiated photon energy, and so their distributions can be imaged. The threshold of electron-hole-pair generation can be varied by changing the irradiated photon energies. Consequently, we can quantitatively image the band-gap energy distributions of semiconductors.

  8. Heteroepitaxy of semiconductors theory, growth, and characterization

    CERN Document Server

    Ayers, John E

    2007-01-01

    Heteroepitaxy has evolved rapidly in recent years. With each new wave of material/substrate combinations, our understanding of how to control crystal growth becomes more refined. Most books on the subject focus on a specific material or material family, narrowly explaining the processes and techniques appropriate for each. Surveying the principles common to all types of semiconductor materials, Heteroepitaxy of Semiconductors: Theory, Growth, and Characterization is the first comprehensive, fundamental introduction to the field. This book reflects our current understanding of nucleation, growth modes, relaxation of strained layers, and dislocation dynamics without emphasizing any particular material. Following an overview of the properties of semiconductors, the author introduces the important heteroepitaxial growth methods and provides a survey of semiconductor crystal surfaces, their structures, and nucleation. With this foundation, the book provides in-depth descriptions of mismatched heteroepitaxy and la...

  9. Nitride semiconductor devices fundamentals and applications

    CERN Document Server

    Morkoç, Hadis

    2013-01-01

    This book gives a clear presentation of the necessary basics of semiconductor and device physics and engineering. It introduces readers to fundamental issues that will enable them to follow the latest technological research. It also covers important applications, including LED and lighting, semiconductor lasers, high power switching devices, and detectors. This balanced and up-to-date treatment makes the text an essential educational tool for both advanced students and professionals in the electronics industry.

  10. Small-signal analysis of granular semiconductors

    Science.gov (United States)

    Varpula, Aapo; Sinkkonen, Juha; Novikov, Sergey

    2010-11-01

    The small-signal ac response of granular n-type semiconductors is calculated analytically using the drift-diffusion theory when electronic trapping at grain boundaries is present. An electrical equivalent circuit (EEC) model of a granular n-type semiconductor is presented. The analytical model is verified with numerical simulation performed by SILVACO ATLAS. The agreement between the analytical and numerical results is very good in a broad frequency range at low dc bias voltages.

  11. Work on the ATLAS semiconductor tracker barrel

    CERN Multimedia

    Maximilien Brice

    2005-01-01

    Precision work is performed on the semiconductor tracker barrel of the ATLAS experiment. All work on these delicate components must be performed in a clean room so that impurities in the air, such as dust, do not contaminate the detector. The semiconductor tracker will be mounted in the barrel close to the heart of the ATLAS experiment to detect the path of particles produced in proton-proton collisions.

  12. Basics of Semiconductor and Spin Physics

    Science.gov (United States)

    Dyakonov, M. I.

    This introductory chapter is mainly addressed to readers new to the field. In Sect. 1.1 a brief review of the historical roots of the current research is given. Section 1.2 describes various spin interactions. Section 1.3 is a mini textbook on semiconductor physics designed for beginners. A short overview of spin phenomena in semiconductors is given in Sect. 1.4. Finally, Sect. 1.5 presents the topics discussed in the chapters to follow.

  13. A Semiconductor Microlaser for Intracavity Flow Cytometry

    Energy Technology Data Exchange (ETDEWEB)

    Akhil, O.; Copeland, G.C.; Dunne, J.L.; Gourley, P.L.; Hendricks, J.K.; McDonald, A.E.

    1999-01-20

    Semiconductor microlasers are attractive components for micro-analysis systems because of their ability to emit coherent intense light from a small aperture. By using a surface-emitting semiconductor geometry, we were able to incorporate fluid flow inside a laser microcavity for the first time. This confers significant advantages for high throughput screening of cells, particulates and fluid analytes in a sensitive microdevice. In this paper we discuss the intracavity microfluidics and present preliminary results with flowing blood and brain cells.

  14. Semiconductor/High-Tc-Superconductor Hybrid ICs

    Science.gov (United States)

    Burns, Michael J.

    1995-01-01

    Hybrid integrated circuits (ICs) containing both Si-based semiconducting and YBa(2)Cu(3)O(7-x) superconducting circuit elements on sapphire substrates developed. Help to prevent diffusion of Cu from superconductors into semiconductors. These hybrid ICs combine superconducting and semiconducting features unavailable in superconducting or semiconducting circuitry alone. For example, complementary metal oxide/semiconductor (CMOS) readout and memory devices integrated with fast-switching Josephson-junction super-conducting logic devices and zero-resistance interconnections.

  15. Diffusion in semiconductors, other than silicon compilation

    CERN Document Server

    Fisher, David J

    2011-01-01

    Review from Book News Inc.: Summary reports of 337 experiments provide information on the diffusion of matter and heat in 31 materials used in semiconductors. Most of the compounds are based on cadmium, gallium, indium, lead, and zinc. Mercury telluride is included however, as is silicon carbide for some reason. Each article is thoroughly referenced to the authors and publication number, date, and page. The arrangement is alphabetical by semiconductor material. Indexes cover authors, hosts, and diffusants.

  16. Semiconductor saturable absorbers for ultrafast terahertz signals

    OpenAIRE

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    2010-01-01

    We demonstrate saturable absorber behavior of n-type semiconductors GaAs, GaP, and Ge in the terahertz THz frequency range at room temperature using nonlinear THz spectroscopy. The saturation mechanism is based on a decrease in electron conductivity of semiconductors at high electron momentum states, due to conduction band onparabolicity and scattering into satellite valleys in strong THz fields. Saturable absorber parameters, such as linear and nonsaturable transmission, and saturation fluen...

  17. Semiconductor saturable absorbers for ultrafast THz signals

    DEFF Research Database (Denmark)

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    We demonstrate saturable absorber behavior of n-type semiconductors in the THz frequency range using nonlinear THz spectroscopy. Further, we observe THz pulse shortening and increase of the group refractive index at high field strengths.......We demonstrate saturable absorber behavior of n-type semiconductors in the THz frequency range using nonlinear THz spectroscopy. Further, we observe THz pulse shortening and increase of the group refractive index at high field strengths....

  18. Semiconductor saturable absorbers for ultrafast terahertz signals

    OpenAIRE

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    2010-01-01

    We demonstrate saturable absorber behavior of n-type semiconductorsGaAs,GaP, and Ge in the terahertz (THz) frequency range at room temperature using nonlinear THz spectroscopy. The saturation mechanism is based on a decrease in electron conductivity of semiconductors at high electron momentum states, due to conduction band nonparabolicity and scattering into satellite valleys in strong THz fields. Saturable absorber parameters, such as linear and nonsaturable transmission, and saturation flue...

  19. Investigation of semiconductor clad optical waveguides

    Science.gov (United States)

    Batchman, T. E.; Carson, R. F.

    1985-01-01

    A variety of techniques have been proposed for fabricating integrated optical devices using semiconductors, lithium niobate, and glasses as waveguides and substrates. The use of glass waveguides and their interaction with thin semiconductor cladding layers was studied. Though the interactions of these multilayer waveguide structures have been analyzed here using glass, they may be applicable to other types of materials as well. The primary reason for using glass is that it provides a simple, inexpensive way to construct waveguides and devices.

  20. Electron gas grid semiconductor radiation detectors

    Science.gov (United States)

    Lee, Edwin Y.; James, Ralph B.

    2002-01-01

    An electron gas grid semiconductor radiation detector (EGGSRAD) useful for gamma-ray and x-ray spectrometers and imaging systems is described. The radiation detector employs doping of the semiconductor and variation of the semiconductor detector material to form a two-dimensional electron gas, and to allow transistor action within the detector. This radiation detector provides superior energy resolution and radiation detection sensitivity over the conventional semiconductor radiation detector and the "electron-only" semiconductor radiation detectors which utilize a grid electrode near the anode. In a first embodiment, the EGGSRAD incorporates delta-doped layers adjacent the anode which produce an internal free electron grid well to which an external grid electrode can be attached. In a second embodiment, a quantum well is formed between two of the delta-doped layers, and the quantum well forms the internal free electron gas grid to which an external grid electrode can be attached. Two other embodiments which are similar to the first and second embodiment involve a graded bandgap formed by changing the composition of the semiconductor material near the first and last of the delta-doped layers to increase or decrease the conduction band energy adjacent to the delta-doped layers.

  1. Thermodynamical limits of diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Buerger, Danilo; Seeger, Michael; Zhou, Shengqiang; Helm, Manfred; Schmidt, Heidemarie [Forschungszentrum Dresden-Rossendorf e.V., Bautzner Landstrasse 400, 01328 Dresden (Germany)

    2010-07-01

    The incorporation of transition metals dopants in semiconductors over their solubility limit is the main challenge for the fabrication of diluted ferromagnetic semiconductors. Dietl et al. calculated the Curie temperatures for various semiconductors doped with 5 at% Mn. A lot of experimental effort was focused on the fabrication of diluted magnetic semiconductors. Unfortunately, such metastable alloys try to reach their thermodynamical equilibrium by the diffusion of the incorporated dopants. The equilibrium state at room temperature for semiconductors with a low solubility of magnetic dopant atoms is characterized by unwanted secondary phases. We present the results from combined random walk simulations and heat-flow calculations and explain the successful fabrication of GaAs:Mn and the impossibility to produce diluted Si:Mn. The clustering process is simulated under the assumption that neighbouring magnetic atoms stick together. This is a general approach for the growth of clusters in supersaturated materials. With the knowledge of the diffusion coefficient our modelling can be used to predict the thermodynamical limit at room temperature and the producibility by pulsed laser annealing of diluted magnetic semiconductors.

  2. Templated Chemically Deposited Semiconductor Optical Fiber Materials

    Science.gov (United States)

    Sparks, Justin R.; Sazio, Pier J. A.; Gopalan, Venkatraman; Badding, John V.

    2013-07-01

    Chemical deposition is a powerful technology for fabrication of planar microelectronics. Optical fibers are the dominant platform for telecommunications, and devices such as fiber lasers are forming the basis for new industries. High-pressure chemical vapor deposition (HPCVD) allows for conformal layers and void-free wires of precisely doped crystalline unary and compound semiconductors inside the micro-to-nanoscale-diameter pores of microstructured optical fibers (MOFs). Drawing the fibers to serve as templates into which these semiconductor structures can be fabricated allows for geometric design flexibility that is difficult to achieve with planar fabrication. Seamless coupling of semiconductor optoelectronic and photonic devices with existing fiber infrastructure thus becomes possible, facilitating all-fiber technological approaches. The deposition techniques also allow for a wider range of semiconductor materials compositions to be exploited than is possible by means of preform drawing. Gigahertz bandwidth junction-based fiber devices can be fabricated from doped crystalline semiconductors, for example. Deposition of amorphous hydrogenated silicon, which cannot be drawn, allows for the exploitation of strong nonlinear optical function in fibers. Finally, crystalline compound semiconductor fiber cores hold promise for high-power infrared light-guiding fiber devices and subwavelength-resolution, large-area infrared imaging.

  3. Electrolysis of a molten semiconductor

    Science.gov (United States)

    Yin, Huayi; Chung, Brice; Sadoway, Donald R.

    2016-01-01

    Metals cannot be extracted by electrolysis of transition-metal sulfides because as liquids they are semiconductors, which exhibit high levels of electronic conduction and metal dissolution. Herein by introduction of a distinct secondary electrolyte, we reveal a high-throughput electro-desulfurization process that directly converts semiconducting molten stibnite (Sb2S3) into pure (99.9%) liquid antimony and sulfur vapour. At the bottom of the cell liquid antimony pools beneath cathodically polarized molten stibnite. At the top of the cell sulfur issues from a carbon anode immersed in an immiscible secondary molten salt electrolyte disposed above molten stibnite, thereby blocking electronic shorting across the cell. As opposed to conventional extraction practices, direct sulfide electrolysis completely avoids generation of problematic fugitive emissions (CO2, CO and SO2), significantly reduces energy consumption, increases productivity in a single-step process (lower capital and operating costs) and is broadly applicable to a host of electronically conductive transition-metal chalcogenides. PMID:27553525

  4. Quantum transport in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, Tillmann Christoph

    2009-11-15

    The main objective of this thesis is to theoretically predict the stationary charge and spin transport in mesoscopic semiconductor quantum devices in the presence of phonons and device imperfections. It is well known that the nonequilibrium Green's function method (NEGF) is a very general and all-inclusive scheme for the description of exactly this kind of transport problem. Although the NEGF formalism has been derived in the 1960's, textbooks about this formalism are still rare to find. Therefore, we introduce the NEGF formalism, its fundamental equations and approximations in the first part of this thesis. Thereby, we extract ideas of several seminal contributions on NEGF in literature and augment this by some minor derivations that are hard to find. Although the NEGF method has often been numerically implemented on transport problems, all current work in literature is based on a significant number of approximations with often unknown influence on the results and unknown validity limits. Therefore, we avoid most of the common approximations and implement in the second part of this thesis the NEGF formalism as exact as numerically feasible. For this purpose, we derive several new scattering self-energies and introduce new self-adaptive discretizations for the Green's functions and self-energies. The most important improvements of our NEGF implementation, however, affect the momentum and energy conservation during incoherent scattering, the Pauli blocking, the current conservation within and beyond the device and the reflectionless propagation through open device boundaries. Our uncommonly accurate implementation of the NEGF method allows us to analyze and assess most of the common approximations and to unveil numerical artifacts that have plagued previous approximate implementations in literature. Furthermore, we apply our numerical implementation of the NEGF method on the stationary electron transport in THz quantum cascade lasers (QCLs) and answer

  5. Majorana fermions in semiconductor nanowires

    Science.gov (United States)

    Stanescu, Tudor D.; Lutchyn, Roman M.; Das Sarma, S.

    2011-10-01

    We study multiband semiconducting nanowires proximity coupled with an s-wave superconductor and calculate the topological phase diagram as a function of the chemical potential and magnetic field. The nontrivial topological state corresponds to a superconducting phase supporting an odd number of pairs of Majorana modes localized at the ends of the wire, whereas the nontopological state corresponds to a superconducting phase with no Majoranas or with an even number of pairs of Majorana modes. Our key finding is that multiband occupancy not only lifts the stringent constraint of one-dimensionality, but also allows having higher carrier density in the nanowire. Consequently, multiband nanowires are better suited for stabilizing the topological superconducting phase and for observing the Majorana physics. We present a detailed study of the parameter space for multiband semiconductor nanowires focusing on understanding the key experimental conditions required for the realization and detection of Majorana fermions in solid-state systems. We include various sources of disorder and characterize their effects on the stability of the topological phase. Finally, we calculate the local density of states as well as the differential tunneling conductance as functions of external parameters and predict the experimental signatures that would establish the existence of emergent Majorana zero-energy modes in solid-state systems.

  6. Real space probe of short-range interaction between Cr in a ferromagnetic semiconductor ZnCrTe.

    Science.gov (United States)

    Kanazawa, Ken; Nishimura, Taku; Yoshida, Shoji; Shigekawa, Hidemi; Kuroda, Shinji

    2014-12-21

    The short-range interaction between Cr atoms was directly examined by scanning tunneling microscopy measurements on a Zn(0.95)Cr(0.05)Te film. Our measurements revealed that a Cr atom formed a localized state within the bandgap of ZnTe and this state was broadened for a pair of Cr atoms within a distance of ∼ 1 nm.

  7. Electron-phonon interaction in a semiconductor quantum wire embedded into the semiconductor medium

    CERN Document Server

    Zharkoj, V P

    2002-01-01

    The renormalization of electron ground state energy due to the different types of interaction with confined (L) and interface (I) phonons in a semiconductor cylindrical quantum wire (QW) embedded into the semiconductor medium by the example of a HgS/CdS nanosystem.

  8. Lateral Mode Control of Semiconductor Lasers

    Science.gov (United States)

    Sun, Yan

    This thesis deals with several topics related to the lateral modes of edge-emitting semiconductor lasers. The first topic is the improvement of lateral beam quality for high power operation. A thermally controlled antiguiding unstable-resonator semiconductor laser with cleaved facets is proposed. With temperature controlled by monolithically integrated micro-heaters, the beam propagation factor is improved by 8 times at 300 mW and by 6 time at 600 mW. The second issue is monolithic semiconductor laser beam steering. Two new mechanisms, thermally controlled offset gain and index guiding lasers and fan laser arrays, have been proposed and demonstrated. They both have single-lobed Gaussian intensity distributions. The fan laser array has shown a total steering angle of 80^circ with eleven resolvable spots, which surpasses the previous results by a factor of three. The third issue is the nonlinear interaction between the semiconductor gain medium and optical waves. The filamentation effect is studied with perturbation theory. Analytical spatial solitary waves have been obtained. The fourth issue is the complex Hermite-Gaussian functions and their applications. An analytical integral expression has been obtained. The generalized complex Gaussian duct is discussed. It is found that the biorthogonal mode expansion and adjoint mode coupling theory in unstable resonators need to be improved. The fifth issue is the lateral modes of stable resonator and stadium resonator semiconductor lasers which have been designed, fabricated and tested. For the stable cavity semiconductor lasers, three distinct operation regions are identified as the stable cavity region, the transition region, and the geometrically unstable region. Preliminary results on stadium resonator semiconductor lasers have also been obtained.

  9. Localized Surface Plasmon Resonance in Semiconductor Nanocrystals.

    Science.gov (United States)

    Agrawal, Ankit; Cho, Shin Hum; Zandi, Omid; Ghosh, Sandeep; Johns, Robert W; Milliron, Delia J

    2018-02-05

    Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals (NCs) that results in resonant absorption, scattering, and near field enhancement around the NC can be tuned across a wide optical spectral range from visible to far-infrared by synthetically varying doping level, and post synthetically via chemical oxidation and reduction, photochemical control, and electrochemical control. In this review, we will discuss the fundamental electromagnetic dynamics governing light matter interaction in plasmonic semiconductor NCs and the realization of various distinctive physical properties made possible by the advancement of colloidal synthesis routes to such NCs. Here, we will illustrate how free carrier dielectric properties are induced in various semiconductor materials including metal oxides, metal chalcogenides, metal nitrides, silicon, and other materials. We will highlight the applicability and limitations of the Drude model as applied to semiconductors considering the complex band structures and crystal structures that predominate and quantum effects that emerge at nonclassical sizes. We will also emphasize the impact of dopant hybridization with bands of the host lattice as well as the interplay of shape and crystal structure in determining the LSPR characteristics of semiconductor NCs. To illustrate the discussion regarding both physical and synthetic aspects of LSPR-active NCs, we will focus on metal oxides with substantial consideration also of copper chalcogenide NCs, with select examples drawn from the literature on other doped semiconductor materials. Furthermore, we will discuss the promise that LSPR in doped semiconductor NCs holds for a wide range of applications such as infrared spectroscopy, energy-saving technologies like smart windows and waste heat management, biomedical applications including therapy and imaging, and optical applications like two photon upconversion, enhanced luminesence, and infrared metasurfaces.

  10. Organic semiconductor distributed feedback lasers

    Science.gov (United States)

    Kowalsky, W.; Rabe, T.; Schneider, D.; Johannes, H.-H.; Karnutsch, C.; Gerken, M.; Lemmer, U.; Wang, J.; Weimann, T.; Hinze, P.; Riedl, T.

    2005-11-01

    Compared to well established liquid based dye lasers, amplifying media based on amorphous organic thin films allow the realisation of versatile, cost effective and compact lasers. Aside from that, the materials involved are organic semiconductors, which in principle allow the fabrication of future electrically driven organic laser diodes. A highly promising, low-loss resonator geometry for these lasers is the distributed feedback (DFB) structure, which is based on a periodic modulation of the refractive index in the waveguide on the nanometer scale. By variation of the grating period Λ one may tune the laser emission within the gain spectrum of the amplifying medium. We will demonstrate organic lasers spanning the entire spectral region from 360-715 nm. Tuning ranges as large as 115 nm (λ = 598-713 nm) in the red spectral region and more than 30 nm (λ = 362-394 nm) in the UV render these novel lasers highly attractive for various spectroscopic applications. As the grating period Λ is typically between 100 nm and 400 nm the DFB resonators are fabricated by e-beam lithography. These gratings may, however, be used as masters to obtain an arbitrary amount of copies by nanoimprint lithography into plastic substrates. Therefore these lasers are very attractive even for single-use applications (e.g. in medicine and biotechnology). Today, the key challenge in the field is the realisation of the first electrically driven organic laser. Key pre-requisites are highly efficient amplifying material systems which allow for low threshold operation and charge transport materials that bring about the stability to sustain the necessary current densities, several orders of magnitude higher than in OLEDs. We will demonstrate diode structures operated electrically under pulsed conditions at current densities up to 760 A/cm2 with a product of the current density and the external quantum effciency (J×η ext) of 1.27 A/cm2. Mechanisms deteriorating the quantum efficieny at elevated

  11. Inorganic Chemistry Solutions to Semiconductor Nanocrystal Problems

    Energy Technology Data Exchange (ETDEWEB)

    Alvarado, Samuel R. [Ames Laboratory; Guo, Yijun [Ames Laboratory; Ruberu, T. Purnima A. [Ames Laboratory; Tavasoli, Elham [Ames Laboratory; Vela, Javier [Ames Laboratory

    2014-03-15

    The optoelectronic and chemical properties of semiconductor nanocrystals heavily depend on their composition, size, shape and internal structure, surface functionality, etc. Available strategies to alter these properties through traditional colloidal syntheses and ligand exchange methods place a premium on specific reaction conditions and surfactant combinations. In this invited review, we apply a molecular-level understanding of chemical precursor reactivity to reliably control the morphology, composition and intimate architecture (core/shell vs. alloyed) of semiconductor nanocrystals. We also describe our work aimed at achieving highly selective, low-temperature photochemical methods for the synthesis of semiconductor–metal and semiconductor–metal oxide photocatalytic nanocomposites. In addition, we describe our work on surface modification of semiconductor nanocrystal quantum dots using new approaches and methods that bypass ligand exchange, retaining the nanocrystal's native ligands and original optical properties, as well as on spectroscopic methods of characterization useful in determining surface ligand organization and chemistry. Using recent examples from our group and collaborators, we demonstrate how these efforts have lead to faster, wider and more systematic application of semiconductor nanocrystal-based materials to biological imaging and tracking, and to photocatalysis of unconventional substrates. We believe techniques and methods borrowed from inorganic chemistry (including coordination, organometallic and solid state chemistry) have much to offer in reaching a better understanding of the synthesis, functionalization and real-life application of such exciting materials as semiconductor nanocrystals (quantum dots, rods, tetrapods, etc.).

  12. Extracting hot carriers from photoexcited semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang

    2014-12-10

    This research program addresses a fundamental question related to the use of nanomaterials in solar energy -- namely, whether semiconductor nanocrystals (NCs) can help surpass the efficiency limits, the so-called “Shockley-Queisser” limit, in conventional solar cells. In these cells, absorption of photons with energies above the semiconductor bandgap generates “hot” charge carriers that quickly “cool” to the band edges before they can be utilized to do work; this sets the solar cell efficiency at a limit of ~31%. If instead, all of the energy of the hot carriers could be captured, solar-to-electric power conversion efficiencies could be increased, theoretically, to as high as 66%. A potential route to capture this energy is to utilize semiconductor nanocrystals. In these materials, the quasi-continuous conduction and valence bands of the bulk semiconductor become discretized due to confinement of the charge carriers. Consequently, the energy spacing between the electronic levels can be much larger than the highest phonon frequency of the lattice, creating a “phonon bottleneck” wherein hot-carrier relaxation is possible via slower multiphonon emission. For example, hot-electron lifetimes as long as ~1 ns have been observed in NCs grown by molecular beam epitaxy. In colloidal NCs, long lifetimes have been demonstrated through careful design of the nanocrystal interfaces. Due to their ability to slow electronic relaxation, semiconductor NCs can in principle enable extraction of hot carriers before they cool to the band edges, leading to more efficient solar cells.

  13. Optical Biosensors Based on Semiconductor Nanostructures

    Directory of Open Access Journals (Sweden)

    Raúl J. Martín-Palma

    2009-06-01

    Full Text Available The increasing availability of semiconductor-based nanostructures with novel and unique properties has sparked widespread interest in their use in the field of biosensing. The precise control over the size, shape and composition of these nanostructures leads to the accurate control of their physico-chemical properties and overall behavior. Furthermore, modifications can be made to the nanostructures to better suit their integration with biological systems, leading to such interesting properties as enhanced aqueous solubility, biocompatibility or bio-recognition. In the present work, the most significant applications of semiconductor nanostructures in the field of optical biosensing will be reviewed. In particular, the use of quantum dots as fluorescent bioprobes, which is the most widely used application, will be discussed. In addition, the use of some other nanometric structures in the field of biosensing, including porous semiconductors and photonic crystals, will be presented.

  14. Developing New Nanoprobes from Semiconductor Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Aihua [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    In recent years, semiconductor nanocrystal quantum dots havegarnered the spotlight as an important new class of biological labelingtool. Withoptical properties superior to conventional organicfluorophores from many aspects, such as high photostability andmultiplexing capability, quantum dots have been applied in a variety ofadvanced imaging applications. This dissertation research goes along withlarge amount of research efforts in this field, while focusing on thedesign and development of new nanoprobes from semiconductor nanocrystalsthat are aimed for useful imaging or sensing applications not possiblewith quantum dots alone. Specifically speaking, two strategies have beenapplied. In one, we have taken advantage of the increasing capability ofmanipulating the shape of semiconductor nanocrystals by developingsemiconductor quantum rods as fluorescent biological labels. In theother, we have assembled quantum dots and gold nanocrystals into discretenanostructures using DNA. The background information and synthesis,surface manipulation, property characterization and applications of thesenew nanoprobes in a few biological experiments are detailed in thedissertation.

  15. Band structure engineering in organic semiconductors

    Science.gov (United States)

    Schwarze, Martin; Tress, Wolfgang; Beyer, Beatrice; Gao, Feng; Scholz, Reinhard; Poelking, Carl; Ortstein, Katrin; Günther, Alrun A.; Kasemann, Daniel; Andrienko, Denis; Leo, Karl

    2016-06-01

    A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials. We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors.

  16. Vertical external cavity surface emitting semiconductor lasers

    CERN Document Server

    Holm, M

    2001-01-01

    Active stabilisation showed a relative locked linewidth of approx 3 kHz. Coarse tuning over 7 nm was achieved using a 3-plate birefingent filter plate while fine-tuning using cavity length change allowed tuning over 250 MHz. Vertical external cavity semiconductor lasers have emerged as an interesting technology based on current vertical cavity semiconductor laser knowledge. High power output into a single transverse mode has attracted companies requiring good fibre coupling for telecommunications systems. The structure comprises of a grown semiconductor Bragg reflector topped with a multiple quantum well gain region. This is then included in an external cavity. This device is then optically pumped to promote laser action. Theoretical modelling of AIGaAs based VECSEL structures was undertaken, showing the effect of device design on laser characteristics. A simple 3-mirror cavity was constructed to assess the static characteristics of the structure. Up to 153 mW of output power was achieved in a single transver...

  17. Reliability and radiation effects in compound semiconductors

    CERN Document Server

    Johnston, Allan

    2010-01-01

    This book discusses reliability and radiation effects in compound semiconductors, which have evolved rapidly during the last 15 years. Johnston's perspective in the book focuses on high-reliability applications in space, but his discussion of reliability is applicable to high reliability terrestrial applications as well. The book is important because there are new reliability mechanisms present in compound semiconductors that have produced a great deal of confusion. They are complex, and appear to be major stumbling blocks in the application of these types of devices. Many of the reliability problems that were prominent research topics five to ten years ago have been solved, and the reliability of many of these devices has been improved to the level where they can be used for ten years or more with low failure rates. There is also considerable confusion about the way that space radiation affects compound semiconductors. Some optoelectronic devices are so sensitive to damage in space that they are very difficu...

  18. High pressure in semiconductor physics II

    CERN Document Server

    Willardson, R K; Suski, Tadeusz; Paul, William

    1998-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The "Willardson and Beer" Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices, Oxygen in Silicon, and others promise indeed that this tra...

  19. Optical Anisotropy of Topologically Distorted Semiconductor Nanocrystals.

    Science.gov (United States)

    Baimuratov, Anvar S; Pereziabova, Tatiana P; Zhu, Weiren; Leonov, Mikhail Yu; Baranov, Alexander V; Fedorov, Anatoly V; Rukhlenko, Ivan D

    2017-09-13

    Engineering nanostructured optical materials via the purposeful distortion of their constituent nanocrystals requires the knowledge of how various distortions affect the nanocrystals' electronic subsystem and its interaction with light. We use the geometric theory of defects in solids to calculate the linear permittivity tensor of semiconductor nanocrystals whose crystal lattice is arbitrarily distorted by imperfections or strains. The result is then employed to systematically analyze the optical properties of nanocrystals with spatial dispersion caused by screw dislocations and Eshelby twists. We demonstrate that Eshelby twists create gyrotropy in nanocrystals made of isotropic semiconductors whereas screw dislocations can produce it only if the nanocrystal material itself is inherently anisotropic. We also show that the dependence of circular dichroism spectrum on the aspect ratio of dislocation-distorted semiconductor nanorods allows resonant enhancing their optical activity (at least by a factor of 2) and creating highly optically active nanomaterials.

  20. Semiconductor laser using multimode interference principle

    Science.gov (United States)

    Gong, Zisu; Yin, Rui; Ji, Wei; Wu, Chonghao

    2018-01-01

    Multimode interference (MMI) structure is introduced in semiconductor laser used in optical communication system to realize higher power and better temperature tolerance. Using beam propagation method (BPM), Multimode interference laser diode (MMI-LD) is designed and fabricated in InGaAsP/InP based material. As a comparison, conventional semiconductor laser using straight single-mode waveguide is also fabricated in the same wafer. With a low injection current (about 230 mA), the output power of the implemented MMI-LD is up to 2.296 mW which is about four times higher than the output power of the conventional semiconductor laser. The implemented MMI-LD exhibits stable output operating at the wavelength of 1.52 μm and better temperature tolerance when the temperature varies from 283.15 K to 293.15 K.

  1. Fundamentals of semiconductors physics and materials properties

    CERN Document Server

    Yu, Peter Y

    1996-01-01

    Fundamentals of Semiconductors attempts to fill the gap between a general solid-state physics textbook and research articles by providing detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors The approach is physical and intuitive rather than formal and pedantic Theories are presented to explain experimental results This textbook has been written with both students and researchers in mind Its emphasis is on understanding the physical properties of Si and similar tetrahedrally coordinated semiconductors The explanations are based on physical insights Each chapter is enriched by an extensive collection of tables of material parameters, figures and problems Many of these problems 'lead the student by the hand' to arrive at the results

  2. Ion beams in semiconductor physics and technology

    Energy Technology Data Exchange (ETDEWEB)

    Kalbitzer, S. (Max-Planck-Inst. fuer Kernphysik, Heidelberg (Germany))

    1992-01-01

    The remarkable progress during the last two decades in semiconductor device technology is partly due to the introduction of ion beams as a key instrument for the modification and analysis of semiconductors. The basic reason is seen in the inherent electrical property of ion beams to be accurately controllable in energy, dose and species. The basic penetration and incorporation mechanisms in elemental and compound semiconductors have been explored and growing agreement between experiment and theory has rendered ion implantation a predictable tool. Similarly, the high analytic potential of nuclear reactions with ion beams has been steadily exploited and outstanding results have been achieved. Some basic milestones in the development of the ion beam techniques will be reviewed and future trends discussed. (orig.).

  3. Fundamentals of semiconductors physics and materials properties

    CERN Document Server

    Yu, Peter Y

    2010-01-01

    This fourth edition of the well-established Fundamentals of Semiconductors serves to fill the gap between a general solid-state physics textbook and research articles by providing detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors. The approach is physical and intuitive rather than formal and pedantic. Theories are presented to explain experimental results. This textbook has been written with both students and researchers in mind. Its emphasis is on understanding the physical properties of Si and similar tetrahedrally coordinated semiconductors. The explanations are based on physical insights. Each chapter is enriched by an extensive collection of tables of material parameters, figures, and problems. Many of these problems "lead the student by the hand" to arrive at the results. The major changes made in the fourth edition include: an extensive appendix about the important and by now well-established deep center known as the DX center, additional problems...

  4. Semiconductor materials for solar photovoltaic cells

    CERN Document Server

    Wong-Ng, Winnie; Bhattacharya, Raghu

    2016-01-01

    This book reviews the current status of semiconductor materials for conversion of sunlight to electricity, and highlights advances in both basic science and manufacturing.  Photovoltaic (PV) solar electric technology will be a significant contributor to world energy supplies when reliable, efficient PV power products are manufactured in large volumes at low cost.  Expert chapters cover the full range of semiconductor materials for solar-to-electricity conversion, from crystalline silicon and amorphous silicon to cadmium telluride, copper indium gallium sulfide selenides, dye sensitized solar cells, organic solar cells, and environmentally friendly copper zinc tin sulfide selenides. The latest methods for synthesis and characterization of solar cell materials are described, together with techniques for measuring solar cell efficiency. Semiconductor Materials for Solar Photovoltaic Cells presents the current state of the art as well as key details about future strategies to increase the efficiency and reduce ...

  5. Hybrid system of semiconductor and photosynthetic protein

    Science.gov (United States)

    Kim, Younghye; Shin, Seon Ae; Lee, Jaehun; Yang, Ki Dong; Nam, Ki Tae

    2014-08-01

    Photosynthetic protein has the potential to be a new attractive material for solar energy absorption and conversion. The development of semiconductor/photosynthetic protein hybrids is an example of recent progress toward efficient, clean and nanostructured photoelectric systems. In the review, two biohybrid systems interacting through different communicating methods are addressed: (1) a photosynthetic protein immobilized semiconductor electrode operating via electron transfer and (2) a hybrid of semiconductor quantum dots and photosynthetic protein operating via energy transfer. The proper selection of materials and functional and structural modification of the components and optimal conjugation between them are the main issues discussed in the review. In conclusion, we propose the direction of future biohybrid systems for solar energy conversion systems, optical biosensors and photoelectric devices.

  6. 76 FR 14688 - In the Matter of Certain Large Scale Integrated Circuit Semiconductor Chips and Products...

    Science.gov (United States)

    2011-03-17

    ... Commission's notice of investigation named several respondents including the following: Freescale Semiconductor Xiqing Integrated Semiconductor Manufacturing Site (``Freescale Xiqing'') of China; Freescale Semiconductor Innovation Center (``Freescale Innovation'') of China; Freescale Semiconductor Pte. Ltd. of...

  7. 75 FR 51843 - In the Matter of Certain Large Scale Integrated Circuit Semiconductor Chips and Products...

    Science.gov (United States)

    2010-08-23

    ... including the following: Freescale Semiconductor Xiqing Integrated Semiconductor Manufacturing Site (``Freescale Xiqing'') of China; Freescale Semiconductor Innovation Center (``Freescale Innovation'') of China; Freescale Semiconductor Pte. Ltd. (``Freescale Pte.'') of Singapore; and Premier Farnell Corporation d/b/a...

  8. Slow and fast light in semiconductor waveguides

    DEFF Research Database (Denmark)

    Mørk, Jesper; Hansen, Per Lunnemann; Xue, Weiqi

    2010-01-01

    transparency and coherent population oscillations. While electromagnetically induced transparency has been the most important effect in realizing slowdown effects in atomic gasses, progress has been comparatively slow in semiconductors due to inherent problems of fast dephasing times and inhomogeneous......Investigations of slow and fast light effects in semiconductor waveguides entail interesting physics and point to a number of promising applications. In this review we give an overview of recent progress in the field, in particular focusing on the physical mechanisms of electromagnetically induced...

  9. Spatial solitons in a pumped semiconductor resonator.

    Science.gov (United States)

    Taranenko, V B; Weiss, C O; Stolz, W

    2001-10-15

    Bright and dark spatial solitons are observed in an optically pumped semiconductor resonator. The pumping allows us to reduce considerably the light intensity necessary for the existence of the solitons and alleviates thermal load problems. Experiments are found to agree qualitatively with calculations based on a simple large-aperture semiconductor resonator model. The role of the signs of the absorptive and reactive nonlinearities in soliton existence is discussed in relation to the nonlinear resonance effect, the tilted-wave mechanism of pattern formation, and the sign of the population inversion.

  10. Quantum theory of electroabsorption in semiconductor nanocrystals.

    Science.gov (United States)

    Tepliakov, Nikita V; Leonov, Mikhail Yu; Baranov, Alexander V; Fedorov, Anatoly V; Rukhlenko, Ivan D

    2016-01-25

    We develop a simple quantum-mechanical theory of interband absorption by semiconductor nanocrystals exposed to a dc electric field. The theory is based on the model of noninteracting electrons and holes in an infinitely deep quantum well and describes all the major features of electroabsorption, including the Stark effect, the Franz-Keldysh effect, and the field-induced spectral broadening. It is applicable to nanocrystals of different shapes and dimensions (quantum dots, nanorods, and nanoplatelets), and will prove useful in modeling and design of electrooptical devices based on ensembles of semiconductor nanocrystals.

  11. Photon recycling semiconductor light-emitting diode

    Science.gov (United States)

    Guo, Xiaoyun; Graff, John W.; Schubert, E. F.; Karlicek, Robert F., Jr.

    2000-04-01

    A new white light emitting diode, the photon recycling semiconductor light emitting diode (PRS-LED) is demonstrated. The device consists of a GaInN/GaN LED emitting in the blue spectral range and an AlGaInP photon recycling semiconductor emitting at the complementary color. Thus the PRS-LED has two emission peaks, one in the blue and one in the amber wavelength range. The theoretical luminous performance of the PRS-LED exceeds 300 lm/W, higher than the performance of phosphor-based white LEDs.

  12. Self-organization in semiconductor physics.

    Science.gov (United States)

    Parisi, J

    1997-01-01

    Non-equilibrium dissipative systems from semiconductor physics have prevailed as a paradigmatic testing field for complex non-linear dynamics during the last decade. Especially, low-temperature impact ionization breakdown in extrinsic germanium crystals displays a variety of interesting nonlinear phenomena, such as spontaneous oscillations and filamentary patterns of the current flow. We report on recent experimental results concerning the interplay between spatial and temporal degrees of freedom during the onset of semiconductor breakdown. Quantitative evaluation of characteristic scaling properties supports the applicability of the model of self-organized criticality.

  13. III-V semiconductor materials and devices

    CERN Document Server

    Malik, R J

    1989-01-01

    The main emphasis of this volume is on III-V semiconductor epitaxial and bulk crystal growth techniques. Chapters are also included on material characterization and ion implantation. In order to put these growth techniques into perspective a thorough review of the physics and technology of III-V devices is presented. This is the first book of its kind to discuss the theory of the various crystal growth techniques in relation to their advantages and limitations for use in III-V semiconductor devices.

  14. Electron-Beam Controlled Semiconductor Switches

    Science.gov (United States)

    1993-11-02

    1987) 153-156. Mazzola , M.S., et al., "Investigation of a Photoconductive Closing and Opening Bulk U GaAs Semiconductor Switch," Proceedings of the...Un-doped GaAs or chromium doped GaAs has decay times of nanoseconds and less. Current scale is 40 mA div-1, time scale is 1000 ns divŕ. (M. Mazzola ...Semiconductor Switch," J. Appl. Phys. 63 (1988) 2460-2463. [5] Mazzola , M., Schoenbach, K., Lakdawala, V., Germer, R., Loubriel, M., and Zutavern, F

  15. Progress in 2D semiconductor optoelectronics

    Science.gov (United States)

    Majumdar, Arka; Fryett, Taylor; Liu, Chang-Hua; Zheng, Jiajiu; Wu, Sanfeng; Rivera, Pasqual; Syler, Kyle; Clark, Genevieve; Xu, Xiaodong

    2017-05-01

    2D semiconductors have recently emerged as promising optoelectronic materials, with high quantum efficiency of photoemission, absorption and nonlinear optical properties. With significant progress in understanding the material science of these atomically thin materials, and building devices with stand-alone monolayer materials, it is an opportune time to integrate these materials with existing optoelectronic platform to realize the full potential of the 2D materials. Here, we highlight our recent progress in 2D semiconductor integrated with nanophotonic resonators. Specifically, we report the operation of an optically pumped laser, cavity enhanced electroluminescence and cavity enhanced second harmonic generation.

  16. Carrier scattering in metals and semiconductors

    CERN Document Server

    Gantmakher, VF

    1987-01-01

    The transport properties of solids, as well as the many optical phenomena in them are determined by the scattering of current carriers. ``Carrier Scattering in Metals and Semiconductors'' elucidates the state of the art in the research on the scattering mechanisms for current carriers in metals and semiconductors and describes experiments in which these mechanisms are most dramatically manifested.The selection and organization of the material is in a form to prepare the reader to reason independently and to deal just as independently with available theoretical results and experimental

  17. Semiconductor surface physics research in the Space Shuttle orbit

    Energy Technology Data Exchange (ETDEWEB)

    Lindau, I.; Spicer, W.E.

    1977-11-01

    The prospects for surface physics research on semiconductors with the Space Shuttle are summarized. The effect of residual gases and solar radiation outside the Shuttle on the semiconductor-surface electronic properties are assessed.

  18. Direct luminescence evidence for the degenerate electron-hole plasma formation in A/sup II/B/sup VI/ semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Brodin, M.S.; Bandura, V.M.; Matsko, M.G. (AN Ukrainskoj SSR, Kiev. Inst. Fiziki)

    1983-09-01

    The emission spectra of ZnTe and ZnSe crystals are investigated at T = 4.2 K at high excitation densities by a Coumarin 30 and 120 dye laser. It is shown that for excitation densities R/sub exc/ > 0.1 MW/cm/sup 2/ the emission spectrum of ZnTe exhibits the P-band due to inelastic exciton-exciton scattering. For R/sub exc/ > 6 MW/cm/sup 2/ the emission of a degenerate electron-hole plasma (EHP) is observed. These emission bands may be differentiated by scanning the exciting quanta energy in the short-wavelength tail region.

  19. Suitability of integrated protection diodes from diverse semiconductor technologies

    NARCIS (Netherlands)

    Wanum, M. van; Lebouille, T.T.N.; Visser, G.C.; Vliet, F.E. van

    2009-01-01

    In this article diodes from three different semiconductor technologies are compared based on their suitability to protect a receiver. The semiconductor materials involved are Silicon, Gallium Arsenide and Gallium Nitride. The diodes in the diverse semiconductor technologies themselves are close in

  20. Point defects in group IV semiconductors

    CERN Document Server

    Pizzini, S

    2017-01-01

    Aim of this book is to focus on the properties of defects in semiconductors of the fourth group under a physico-chemical approach, capable to demonstrate whether the full acknowledgement of their chemical nature could account for several problems encountered in practice or would suggest further experimental or theoretical accomplishments.

  1. Physics of semiconductors in high magnetic fields

    CERN Document Server

    Miura, Noboru

    2008-01-01

    This book summarizes most of the fundamental physical phenomena which semiconductors and their modulated structures exhibit in high magnetic fields. Readers can learn not only the basic theoretical background but also the present state of the art from the most advanced data in this rapidly growing research area.

  2. SCOOP - Semiconductor COmponents for Optical signal Processing

    DEFF Research Database (Denmark)

    Mørk, Jesper; Yvind, Kresten; Oxenløwe, Leif Katsuo

    2001-01-01

    Opto-electronic semiconductor devices operating at very high bitrates play a central role in the continued expansion of the transmission capacity of optical communication systems. A number of different devices based on quantum well structures have been manufactured within the framework of the nat...

  3. Opportunities and Risks in Semiconductor Metrology

    Science.gov (United States)

    Borden, Peter

    2005-09-01

    New metrology opportunities are constantly emerging as the semiconductor industry attempts to meet scaling requirements. The paper summarizes some of the key FEOL and BEOL needs. These must be weighed against a number of considerations to ensure that they are good opportunities for the metrology equipment supplier. The paper discusses some of these considerations.

  4. Ballistic transport in semiconductor nanostructures: From quasi ...

    Indian Academy of Sciences (India)

    By suitable design it is possible to achieve quasi-ballistic transport in semiconductor nanostructures over times up to the ps-range. Monte-Carlo simulations reveal that under these conditions phase-coherent real-space oscillations of an electron ensemble, generated by fs-pulses become possible in wide potential wells.

  5. Impact of nano particles on semiconductor manufacturing

    NARCIS (Netherlands)

    Wali, F.; Knotter, D.M.; Kuper, F.G.

    2008-01-01

    Semiconductor industry faces a continuous challenge to decrease the transistor size as well as to increase the yield by eliminating defect sources. One of the sources of particle defects is ultra pure water used in different production tools at different stages of processing. In this paper, particle

  6. New semiconductor materials for magnetoelectronics at room ...

    Indian Academy of Sciences (India)

    Unknown

    inherent advantage of magnetoelectronics over electronics is the fact that magnet tend to stay magnetized for long. Hence this arises interest in industries to replace the semiconductor-based components of computer with mag- netic ones, starting from RAM. The new magnetic RAM will retain data even when the computer is ...

  7. Competing interactions in semiconductor quantum dots

    NARCIS (Netherlands)

    van den Berg, R.; Brandino, G.P.; El Araby, O.; Konik, R.M.; Gritsev, V.; Caux, J.S.

    2014-01-01

    We introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free-induction decay and spin-echo simulations

  8. Automated semiconductor vacuum chemical vapor deposition facility

    Science.gov (United States)

    1982-01-01

    A semiconductor vacuum chemical vapor deposition facility (totally automatic) was developed. Wafers arrived on an air track, automatically loaded into a furnace tube, processed, returned to the track, and sent on to the next operation. The entire process was controlled by a computer.

  9. Semiconductor nanowire optical antenna solar absorbers.

    Science.gov (United States)

    Cao, Linyou; Fan, Pengyu; Vasudev, Alok P; White, Justin S; Yu, Zongfu; Cai, Wenshan; Schuller, Jon A; Fan, Shanhui; Brongersma, Mark L

    2010-02-10

    Photovoltaic (PV) cells can serve as a virtually unlimited clean source of energy by converting sunlight into electrical power. Their importance is reflected in the tireless efforts that have been devoted to improving the electrical and structural properties of PV materials. More recently, photon management (PM) has emerged as a powerful additional means to boost energy conversion efficiencies. Here, we demonstrate an entirely new PM strategy that capitalizes on strong broad band optical antenna effects in one-dimensional semiconductor nanostructures to dramatically enhance absorption of sunlight. We show that the absorption of sunlight in Si nanowires (Si NWs) can be significantly enhanced over the bulk. The NW's optical properties also naturally give rise to an improved angular response. We propose that by patterning the silicon layer in a thin film PV cell into an array of NWs, one can boost the absorption for solar radiation by 25% while utilizing less than half of the semiconductor material (250% increase in the light absorption per unit volume of material). These results significantly advance our understanding of the way sunlight is absorbed by one-dimensional semiconductor nanostructures and provide a clear, intuitive guidance for the design of efficient NW solar cells. The presented approach is universal to any semiconductor and a wide range of nanostructures; as such, it provides a new PV platform technology.

  10. UK semiconductor tracker parts head for CERN

    CERN Multimedia

    Holland, Colin

    2005-01-01

    The last of the 4 barrels that make up the central part of the Semiconductor Tracker (SCT), the heart of the biggest physics collaboration in the world have left Oxford for its new home at the European Particle Physics Laboratory, CERN, near Geneva

  11. Theory of mode-locked semiconductor lasers.

    NARCIS (Netherlands)

    Leegwater, J.A.

    1996-01-01

    We present a theoretical study of semiconductor mode-locked lasers at a phenomenological level. We use the slow absorber model of New and Haus, but extend the analysis by taking into account the shift in the gain maximum due to the changing number of carriers. In our analysis of the resulting

  12. Ultrafast THz Saturable Absorption in Semiconductors

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hoffmann, Matthias C.

    2011-01-01

    We demonstrate THz saturable absorption in n-doped semiconductors GaAs, GaP, and Ge in a nonlinear THz time-domain spectroscopy experiment. Saturable absorption is caused by sample conductivity modulation due to electron heating and satellite valley scattering in the field of a strong THz pulse....

  13. Ultranarrow polaritons in a semiconductor microcavity

    DEFF Research Database (Denmark)

    Jensen, Jacob Riis; Borri, Paola; Langbein, Wolfgang

    2000-01-01

    We have achieved a record high ratio (19) of the Rabi splitting (3.6 meV) to the polariton linewidth (190 mu eV), in a semiconductor lambda microcavity with a single 25 nm GaAs quantum well at the antinode. The narrow polariton lines are obtained with a special cavity design which reduces...

  14. Niobium Nitride Josephson Devices with Semiconductor Barriers.

    Science.gov (United States)

    1981-09-01

    impedance of the semiconductor side of the device.17 (An exception is the silicon membrane structures of Huang and Van Duzer . 2) In our devices this...and T. Van Duzer , Appl. Phys. Lett. 25, 753 (1974). 3. M. Schyfter, J. Maah-Sango, N. Ralez, R. Rubz, B. T. Alrich, and T. Van Duzer , IEEE Trans

  15. Neutron Detection with Cryogenics and Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    bell, Z.W.; Carpenter, D.A.; Cristy, S.S.; Lamberti, V.E.

    2005-03-10

    The common methods of neutron detection are reviewed with special attention paid to the application of cryogenics and semiconductors to the problem. The authors' work with LiF- and boron-based cryogenic instruments is described as well as the use of CdTe and HgI{sub 2} for direct detection of neutrons.

  16. Optical Properties of Semiconductor Quantum Dots

    NARCIS (Netherlands)

    Perinetti, U.

    2011-01-01

    This thesis presents different optical experiments performed on semiconductor quantum dots. These structures allow to confine a small number of electrons and holes to a tiny region of space, some nm across. The aim of this work was to study the basic properties of different types of quantum dots

  17. A hybrid semiconductor-glass waveguide laser

    NARCIS (Netherlands)

    Fan, Youwen; Oldenbeuving, Ruud; Klein, E.J.; Lee, Christopher James; Song, H.; Khan, M.R.H.; Offerhaus, Herman L.; van der Slot, Petrus J.M.; Boller, Klaus J.; Mackenzie, J.I.; Jelinkova, H.; Taira, T.; Ahmed, M.A.

    2014-01-01

    abstract .We report on a novel type of laser in which a semiconductor optical amplifier (SOA) receives frequency-selective feedback from a glass-waveguide circuit. The laser we present here is based on InP for operation in the 1.55 μm wavelength range. The Si3N4/SiO2 glass waveguide circuit

  18. A hybrid semiconductor-glass waveguide laser

    NARCIS (Netherlands)

    Fan, Y.; Oldenbeuving, R.M.; Klein, E.J.; Lee, C.J.; Song, H.; Khan, M.R.H.; Offerhaus, H.L.; Van der Slot, P.J.M.; Boller, K.J.

    2014-01-01

    We report on a novel type of laser in which a semiconductor optical amplifier (SOA) receives frequency-selective feedback from a glass-waveguide circuit. The laser we present here is based on InP for operation in the 1.55 µm wavelength range. The Si3N4/SiO2 glass waveguide circuit comprises two

  19. Emission and Absorption Entropy Generation in Semiconductors

    DEFF Research Database (Denmark)

    Reck, Kasper; Varpula, Aapo; Prunnila, Mika

    2013-01-01

    materials due to emission and absorption of electromagnetic radiation. It is shown that the emission and absorption entropy generation reduces the fundamental limit on the efficiency of any semiconductor solar cell even further than the Landsberg limit. The results are derived from purely thermodynamical...

  20. Method for manufacturing a semiconductor device

    NARCIS (Netherlands)

    Ishihara, R.; Baiano, A.

    2009-01-01

    The invention relates to a method for manufacturing a semiconductor device on a substrate provided with a silicon-oxide layer, by forming at least one hole in said silicon-oxide layer and depositing on said silicon-oxide layer an amorphous silicon-film which fills said at least one hole and covers a

  1. The Quantum Boltzmann Equation in Semiconductor Physics

    OpenAIRE

    Snoke, D. W.

    2010-01-01

    The quantum Boltzmann equation, or Fokker-Planck equation, has been used to successfully explain a number of experiments in semiconductor optics in the past two decades. This paper reviews some of the developments of this work, including models of excitons in bulk materials, electron-hole plasmas, and polariton gases.

  2. Bipolar magnetic semiconductor in silicene nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Farghadan, Rouhollah, E-mail: rfarghadan@kashanu.ac.ir

    2017-08-01

    Highlights: • A new electronic phase for silicene nanoribbon in the presence of electric and magnetic fields. • Bipolar magnetic semiconductor with controllable spin-flip and spin-conserved gaps in silicene. • Robust bipolar magnetic semiconductor features in a rough silicene. • Perfect and reversible spin polarization in silicene nanoribbon junctions. - Abstract: A theoretical study was presented on generation of spin polarization in silicene nanoribbons using the single-band tight-binding approximation and the non-equilibrium Green’s function formalism. We focused on the effect of electric and exchange magnetic fields on the spin-filter capabilities of zigzag-edge silicene nanoribbons in the presence of the intrinsic spin-orbit interaction. The results show that a robust bipolar magnetic semiconductor with controllable spin-flip and spin-conserved gaps can be obtained when exchange magnetic and electric field strengths are both larger than the intrinsic spin-orbit interaction. Therefore, zigzag silicene nanoribbons could act as bipolar and perfect spin filter devices with a large spin-polarized current and a reversible spin polarization in the vicinity of the Fermi energy. We also investigated the effect of edge roughness and found that the bipolar magnetic semiconductor features are robust against edge disorder in silicene nanoribbon junctions. These results may be useful in multifunctional spin devices based on silicene nanoribbons.

  3. Tunneling of electrons through semiconductor superlattices

    Indian Academy of Sciences (India)

    Unknown

    The SSL we have considered is Ga0⋅7Al0⋅3As–GaAs which has been drawing considerable attention during the recent past on account of some typical features of its band structure. We have indicated how our results would help fabrication of ultra high speed devices. Keywords. Semiconductor superlattices; tunneling. 1.

  4. Semiconductor detectors with proximity signal readout

    Energy Technology Data Exchange (ETDEWEB)

    Asztalos, Stephen J. [XIA, LLC, Hayward, CA (United States)

    2014-01-30

    Semiconductor-based radiation detectors are routinely used for the detection, imaging, and spectroscopy of x-rays, gamma rays, and charged particles for applications in the areas of nuclear and medical physics, astrophysics, environmental remediation, nuclear nonproliferation, and homeland security. Detectors used for imaging and particle tracking are more complex in that they typically must also measure the location of the radiation interaction in addition to the deposited energy. In such detectors, the position measurement is often achieved by dividing or segmenting the electrodes into many strips or pixels and then reading out the signals from all of the electrode segments. Fine electrode segmentation is problematic for many of the standard semiconductor detector technologies. Clearly there is a need for a semiconductor-based radiation detector technology that can achieve fine position resolution while maintaining the excellent energy resolution intrinsic to semiconductor detectors, can be fabricated through simple processes, does not require complex electrical interconnections to the detector, and can reduce the number of required channels of readout electronics. Proximity electrode signal readout (PESR), in which the electrodes are not in physical contact with the detector surface, satisfies this need.

  5. Dispersion-induced nonlinearities in semiconductors

    DEFF Research Database (Denmark)

    Mørk, Jesper; Mecozzi, A.

    2002-01-01

    A dispersive and saturable medium is shown, under very general conditions, to possess ultrafast dynamic behaviour due to non-adiabatic polarisation dynamics. Simple analytical expressions relating the effect to the refractive index dispersion of a semiconductor ire derived and the magnitude...

  6. Electrostatic model of semiconductor nanoparticles trapped in ...

    Indian Academy of Sciences (India)

    A simple electrostatic model is applied to study the solvation energy and localization energy to inorganic semiconductor nanocrystallites trapped in polymer and ion conducting ... In the single charge configuration, the dielectric constant of the medium has been identified as the selection criteria for hosting the nanoparticles.

  7. Revenue sharing in semiconductor industry supply chain ...

    Indian Academy of Sciences (India)

    This paper defines cooperation as the process of coordinating the objectives and activities of supply chain (SC) members. It also focuses on cooperation as a solution for hybrid coordination mechanism to form the basis for semiconductor industry supply chain management. In the complex and competitive environment of ...

  8. Testing of modern semiconductor memory structures

    NARCIS (Netherlands)

    Gaydadjiev, G.N.

    2007-01-01

    In this thesis, we study the problem of faults in modern semiconductor memory structures and their tests. According to the 2005 ITRS, the systems on chip (SoCs) are moving from logic and memory balanced chips to more memory dominated devices in order to cope with the increasing application

  9. Scientific Description of Summer Semiconductor Program

    Science.gov (United States)

    1991-03-02

    EE/CS 3-180 9:30 am Carlo Cercignani Methods of the kinetic theory of gases relevant Politecuico di Milsao to the kinetic models for semiconductors...Pittsburgh Jul 15-Aug 9 Cercignani , Carlo Politecnico di Milano Jul 21-Aug 3 Cole, Dan IBM GPD Jul 24-Aug 1 Cole, J-dian Rensselaer Polytechnic Institute

  10. Semiconductor devices for all-optical regeneration

    DEFF Research Database (Denmark)

    Öhman, Filip; Bischoff, Svend; Tromborg, Bjarne

    2003-01-01

    We review different implementations of semiconductor devices for all-optical regeneration. A general model will be presented for all-optical regeneration in fiber links, taking into consideration the trade-off between non-linearity and noise. Furthermore we discuss a novel regenerator type, based...

  11. Many electron effects in semiconductor quantum dots

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 26; Issue 1. Many electron effects in ... Semiconductor quantum dots (QDs) exhibit shell structures, very similar to atoms. Termed as 'artificial atoms' by some, ... Our calculations have been performed in a three-dimensional quantum dot. We have carried out a study of ...

  12. Picosecond Nonlinear Resonant Interactions in Semiconductors.

    Science.gov (United States)

    1986-03-01

    1985). 3. "Electron-Hole Recombination Spectra and Kinetics in PbTc/PbEuTcSc Multiple Quamtum Wells", W. Goltsos, J. Nakahara, A. V. Nurmikko, and D...Partin, Proc. Int. Conf. Modulated Semiconductor Structures, Kyoto, Surface Science (in press). 4. "Optical Bandgap and Magneto-Optical Effects in (Pb,Eu

  13. A Semiconductor Nanowire-Based Superconducting Qubit

    DEFF Research Database (Denmark)

    Larsen, T. W.; Petersson, K. D.; Kuemmeth, F.

    2015-01-01

    We introduce a hybrid qubit based on a semiconductor nanowire with an epitaxially grown superconductor layer. Josephson energy of the transmon-like device ("gatemon") is controlled by an electrostatic gate that depletes carriers in a semiconducting weak link region. Strong coupling to an on...

  14. All optical regeneration using semiconductor devices

    DEFF Research Database (Denmark)

    Mørk, Jesper; Öhman, Filip; Tromborg, Bjarne

    All-optical regeneration is a key functionality for implementing all-optical networks. We present a simple theory for the bit-error-rate in links employing all-optical regenerators, which elucidates the interplay between the noise and and nonlinearity of the regenerator. A novel device structure ...... is analyzed, emphasizing general aspects of active semiconductor waveguides....

  15. Electron Spins in Semiconductor Quantum Dots

    NARCIS (Netherlands)

    Hanson, R.

    2005-01-01

    This thesis describes a series of experiments aimed at understanding and controlling the behavior of the spin degree of freedom of single electrons, confined in semiconductor quantum dots. This research work is motivated by the prospects of using the electron spin as a quantum bit (qubit), the basic

  16. Semiconductor applications of plasma immersion ion implantation ...

    Indian Academy of Sciences (India)

    Many semiconductor integrated circuit manufacturing processes require high dose of implantation at very low energies. Conventional beam line ion implantation system suffers from low beam current at low energies, therefore, cannot be used economically for high dose applications. Plasma immersion ion implantation (PIII) ...

  17. Electrostatic model of semiconductor nanoparticles trapped in ...

    Indian Academy of Sciences (India)

    Abstract. A simple electrostatic model is applied to study the solvation energy and localization energy to inorganic semiconductor nanocrystallites trapped in polymer and ion conducting polymer electrolytes. The effective mass approximation has been applied to the system. In the single charge configuration, the dielectric ...

  18. Trap level spectroscopy in amorphous semiconductors

    CERN Document Server

    Mikla, Victor V

    2010-01-01

    Although amorphous semiconductors have been studied for over four decades, many of their properties are not fully understood. This book discusses not only the most common spectroscopic techniques but also describes their advantages and disadvantages.Provides information on the most used spectroscopic techniquesDiscusses the advantages and disadvantages of each technique

  19. Robust high aspect ratio semiconductor device

    NARCIS (Netherlands)

    Roozeboom, F.; Goossens, M.; Besling, W.F.A.; Verhaegh, N.

    2014-01-01

    The invention relates to an semi-conductor device comprising a first surface and neighboring first and second electric elements arranged on the first surface, in which each of the first and second elements extends from the first surface in a first direction, the first element having a cross section

  20. Stimulated secondary emission from semiconductor microcavities

    DEFF Research Database (Denmark)

    Østergaard, John Erland; Mizeikis, V.; Langbein, Wolfgang Werner

    2001-01-01

    We find strong influence of final-state stimulation on the time-resolved light emission dynamics from semiconductor microcavities after pulsed excitation allowing angle-resonant polariton-polariton scattering on the lower-polariton branch. The polariton dynamics can be controlled by injection of ...

  1. EDITORIAL The 23rd Nordic Semiconductor Meeting The 23rd Nordic Semiconductor Meeting

    Science.gov (United States)

    Ólafsson, Sveinn; Sveinbjörnsson, Einar

    2010-12-01

    A Nordic Semiconductor Meeting is held every other year with the venue rotating amongst the Nordic countries of Denmark, Finland, Iceland, Norway and Sweden. The focus of these meetings remains 'original research and science being carried out on semiconductor materials, devices and systems'. Reports on industrial activity have usually featured. The topics have ranged from fundamental research on point defects in a semiconductor to system architecture of semiconductor electronic devices. Proceedings from these events are regularly published as a topical issue of Physica Scripta. All of the papers in this topical issue have undergone critical peer review and we wish to thank the reviewers and the authors for their cooperation, which has been instrumental in meeting the high scientific standards and quality of the series. This meeting of the 23rd Nordic Semiconductor community, NSM 2009, was held at Háskólatorg at the campus of the University of Iceland, Reykjavik, Iceland, 14-17 June 2009. Support was provided by the University of Iceland. Almost 50 participants presented a broad range of topics covering semiconductor materials and devices as well as related material science interests. The conference provided a forum for Nordic and international scientists to present and discuss new results and ideas concerning the fundamentals and applications of semiconductor materials. The meeting aim was to advance the progress of Nordic science and thus aid in future worldwide technological advances concerning technology, education, energy and the environment. Topics Theory and fundamental physics of semiconductors Emerging semiconductor technologies (for example III-V integration on Si, novel Si devices, graphene) Energy and semiconductors Optical phenomena and optical devices MEMS and sensors Program 14 June Registration 13:00-17:00 15 June Meeting program 09:30-17:00 and Poster Session I 16 June Meeting program 09:30-17:00 and Poster Session II 17 June Excursion and dinner

  2. The AMOS cell - An improved metal-semiconductor solar cell. [Antireflection coated Metal Oxide Semiconductor

    Science.gov (United States)

    Stirn, R. J.; Yeh, Y.-C. M.

    1975-01-01

    A new fabrication process is being developed which significantly improves the efficiency of metal-semiconductor solar cells. The resultant effect, a marked increase in the open-circuit voltage, is produced by the addition of an interfacial layer oxide on the semiconductor. Cells using gold on n-type gallium arsenide have been made in small areas (0.17 sq cm) with conversion efficiencies of 15% in terrestrial sunlight.

  3. Electronic states of semiconductor-metal-semiconductor quantum-well structures

    Science.gov (United States)

    Huberman, M. L.; Maserjian, J.

    1988-01-01

    Quantum-size effects are calculated in thin layered semiconductor-metal-semiconductor structures using an ideal free-electron model for the metal layer. The results suggest new quantum-well structures having device applications. Structures with sufficiently high-quality interfaces should exhibit effects such as negative differential resistance due to tunneling between allowed states. Similarly, optical detection by intersubband absorption may be possible. Ultrathin metal layers are predicted to behave as high-density dopant sheets.

  4. Doped semiconductors and semiconductor devices as model systems for fundamental condensed matter physics

    Energy Technology Data Exchange (ETDEWEB)

    Berggren, K.-F.

    1983-02-01

    Doped semiconductors and semiconductor devices are discussed with emphasis on fundamental physical phenomena. It is argued that such systems are ideal model systems for condensed matter physics in general. This view point is illustrated by a few examples such as the amorphous antiferromagnetism associated with non-metallic Si:P and effects of weak localization in metallic Si:P and a GaAs field effect transistor.

  5. Architectures for Improved Organic Semiconductor Devices

    Science.gov (United States)

    Beck, Jonathan H.

    Advancements in the microelectronics industry have brought increasing performance and decreasing prices to a wide range of users. Conventional silicon-based electronics have followed Moore's law to provide an ever-increasing integrated circuit transistor density, which drives processing power, solid-state memory density, and sensor technologies. As shrinking conventional integrated circuits became more challenging, researchers began exploring electronics with the potential to penetrate new applications with a low price of entry: "Electronics everywhere." The new generation of electronics is thin, light, flexible, and inexpensive. Organic electronics are part of the new generation of thin-film electronics, relying on the synthetic flexibility of carbon molecules to create organic semiconductors, absorbers, and emitters which perform useful tasks. Organic electronics can be fabricated with low energy input on a variety of novel substrates, including inexpensive plastic sheets. The potential ease of synthesis and fabrication of organic-based devices means that organic electronics can be made at very low cost. Successfully demonstrated organic semiconductor devices include photovoltaics, photodetectors, transistors, and light emitting diodes. Several challenges that face organic semiconductor devices are low performance relative to conventional devices, long-term device stability, and development of new organic-compatible processes and materials. While the absorption and emission performance of organic materials in photovoltaics and light emitting diodes is extraordinarily high for thin films, the charge conduction mobilities are generally low. Building highly efficient devices with low-mobility materials is one challenge. Many organic semiconductor films are unstable during fabrication, storage, and operation due to reactions with water, oxygen and hydroxide. A final challenge facing organic electronics is the need for new processes and materials for electrodes

  6. Semiconductor Photocatalysis for Chemoselective Radical Coupling Reactions.

    Science.gov (United States)

    Kisch, Horst

    2017-04-18

    Photocatalysis at semiconductor surfaces is a growing field of general photocatalysis because of its importance for the chemical utilization of solar energy. By analogy with photoelectrochemistry the basic mechanism of semiconductor photocatalysis can be broken down into three steps: photogenerated formation of surface redox centers (electron-hole pairs), interfacial electron transfer from and to substrates (often coupled with proton-transfer), and conversion of primary redox intermediates into the products. Sun driven water cleavage and carbon dioxide fixation are still in the state of basic research whereas aerial degradation reactions of pollutants have reached practical application for the cleaning of air. In addition, a great variety of organic transformations (not syntheses) have been reported. They include cis-trans isomerizations, valence isomerizations, cycloaddition reactions, intramolecular or intermolecular C-N and C-C couplings, partial oxidations, and reductions. In all cases, well-known products were formed but very rarely also isolated. As compared to conventional homogeneous organic synthesis, the photocatalytic reaction mode is of no advantage, although the opposite is quite often claimed in the literature. It is also noted that a high quantum yield does not implicate a high product yield, since it is measured at very low substrate conversion in order to minimize secondary photoreactions. That is especially important in semiconductor photocatalysis since photocorrosion of the photocatalyst often prevents long-time irradiation, as is the case for colloidal metal sulfide semiconductors, which in general are photochemically too unstable to be used in synthesis. In this Account, we first classify the numerous organic photoreactions catalyzed by semiconductor powders. The classification is based on easily obtainable experimental facts, namely the nature of the light absorbing reaction component and the reaction stoichiometry. Next we discuss the

  7. Report on achievement in developing an ultra low loss power element technology. Survey on practical application of the next generation power semiconductor devices; 1998 nendo choteisonshitsu denryoku soshi gijutsu kaihatsu seika hokokusho. Jisedai power handotai device jitsuyoka chosa

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-03-01

    Trends were surveyed for development of an ultra low loss power element. Performance improvement has been progressed on power semiconductor elements by using Si as the raw material, but loss reduction has come close to the physical limit. SiC is expected of possibility to go beyond this limit. SiC is so very excellent that its band gap is two to three times greater, insulation breakdown electric field is 7.5 times higher, temperature to become a true semiconductor is three to four times higher than those of Si. The wide gap can reduce high temperature leaking current in p-n junctions, and the increased authenticity temperature can increase the upper limit for operation temperature. The insulation breakdown strength being higher by one digit can reduce the drift layer thickness, and is expected to dramatically reduce the loss. The problem is that high quality crystals have not been obtained to date. One of the promising application fields is electric vehicle. The device currently using the power element in the largest scale is used in frequency converting stations to link the 50-Hz power network in the eastern part of Japan to the 60-Hz network in the western part of Japan. Surveys were carried out on the Sakuma frequency converting station and the New Shinano substation. (NEDO)

  8. The Physics of Semiconductors An Introduction Including Devices and Nanophysics

    CERN Document Server

    Grundmann, Marius

    2006-01-01

    The Physics of Semiconductors provides material for a comprehensive upper-level-undergrauate and graduate course on the subject, guiding readers to the point where they can choose a special topic and begin supervised research. The textbook provides a balance between essential aspects of solid-state and semiconductor physics, on the one hand, and the principles of various semiconductor devices and their applications in electronic and photonic devices, on the other. It highlights many practical aspects of semiconductors such as alloys, strain, heterostructures, nanostructures, that are necessary in modern semiconductor research but typically omitted in textbooks. For the interested reader some additional advanced topics are included, such as Bragg mirrors, resonators, polarized and magnetic semiconductors are included. Also supplied are explicit formulas for many results, to support better understanding. The Physics of Semiconductors requires little or no prior knowledge of solid-state physics and evolved from ...

  9. The Physics of Semiconductors An Introduction Including Nanophysics and Applications

    CERN Document Server

    Grundmann, Marius

    2010-01-01

    The Physics of Semiconductors contains ample material for a comprehensive upper-level undergraduate or beginning graduate course, guiding readers to the point where they can choose a special topic and begin supervised research. The textbook provides a balance between essential aspects of solid-state and semiconductor physics, on the one hand, and the principles of various semiconductor devices and their applications in electronic and photonic devices, on the other. It highlights many practical aspects of semiconductors such as alloys, strain, heterostructures, nanostructures, that are necessary in modern semiconductor research but typically omitted in textbooks. Coverage also includes additional advanced topics, such as Bragg mirrors, resonators, polarized and magnetic semiconductors. The text derives explicit formulas for many results to support better understanding of the topics. The Physics of Semiconductors requires little or no prior knowledge of solid-state physics and evolved from a highly regarded two...

  10. EDITORIAL: Frontiers in semiconductor-based devices Frontiers in semiconductor-based devices

    Science.gov (United States)

    Krishna, Sanjay; Phillips, Jamie; Ghosh, Siddhartha; Ma, Jack; Sabarinanthan, Jayshri; Stiff-Roberts, Adrienne; Xu, Jian; Zhou, Weidong

    2009-12-01

    This special cluster of Journal of Physics D: Applied Physics reports proceedings from the Frontiers in Semiconductor-Based Devices Symposium, held in honor of the 60th birthday of Professor Pallab Bhattacharya by his former doctoral students. The symposium took place at the University of Michigan, Ann Arbor on 6-7 December 2009. Pallab Bhattacharya has served on the faculty of the Electrical Engineering and Computer Science Department at the University of Michigan, Ann Arbor for 25 years. During this time, he has made pioneering contributions to semiconductor epitaxy, characterization of strained heterostructures, self-organized quantum dots, quantum-dot optoelectronic devices, and integrated optoelectronics. Professor Bhattacharya has been recognized for his accomplishments by membership of the National Academy of Engineering, by chaired professorships (Charles M Vest Distinguished University Professor and James R Mellor Professor of Engineering), and by selection as a Fellow of the IEEE, among numerous other honors and awards. Professor Bhattacharya has also made remarkable contributions in education, including authorship of the textbook Semiconductor Optoelectronic Devices (Prentice Hall, 2nd edition) and the production of 60 PhD students (and counting). In fact, this development of critical human resources is one of the biggest impacts of Professor Bhattacharya's career. His guidance and dedication have shaped the varied professional paths of his students, many of whom currently enjoy successful careers in academia, industry, and government around the world. This special cluster acknowledges the importance of Professor Bhattacharya's influence as all of the contributions are from his former doctoral students. The symposium reflects the significant impact of Professor Bhattacharya's research in that the topics span diverse, critical research areas, including: semiconductor lasers and modulators, nanoscale quantum structure-based devices, flexible CMOS

  11. Semiconductor quantum dot-sensitized solar cells

    Directory of Open Access Journals (Sweden)

    Jianjun Tian

    2013-10-01

    Full Text Available Semiconductor quantum dots (QDs have been drawing great attention recently as a material for solar energy conversion due to their versatile optical and electrical properties. The QD-sensitized solar cell (QDSC is one of the burgeoning semiconductor QD solar cells that shows promising developments for the next generation of solar cells. This article focuses on recent developments in QDSCs, including 1 the effect of quantum confinement on QDSCs, 2 the multiple exciton generation (MEG of QDs, 3 fabrication methods of QDs, and 4 nanocrystalline photoelectrodes for solar cells. We also make suggestions for future research on QDSCs. Although the efficiency of QDSCs is still low, we think there will be major breakthroughs in developing QDSCs in the future.

  12. Spectroscopy of organic semiconductors from first principles

    Science.gov (United States)

    Sharifzadeh, Sahar; Biller, Ariel; Kronik, Leeor; Neaton, Jeffery

    2011-03-01

    Advances in organic optoelectronic materials rely on an accurate understanding their spectroscopy, motivating the development of predictive theoretical methods that accurately describe the excited states of organic semiconductors. In this work, we use density functional theory and many-body perturbation theory (GW/BSE) to compute the electronic and optical properties of two well-studied organic semiconductors, pentacene and PTCDA. We carefully compare our calculations of the bulk density of states with available photoemission spectra, accounting for the role of finite temperature and surface effects in experiment, and examining the influence of our main approximations -- e.g. the GW starting point and the application of the generalized plasmon-pole model -- on the predicted electronic structure. Moreover, our predictions for the nature of the exciton and its binding energy are discussed and compared against optical absorption data. We acknowledge DOE, NSF, and BASF for financial support and NERSC for computational resources.

  13. The Optimal Decision Combination in Semiconductor Manufacturing

    Directory of Open Access Journals (Sweden)

    Sungwook Yoon

    2017-10-01

    Full Text Available Wafer fabrication is a capital-intensive and highly complex manufacturing process. In a wafer fabrication facility (fab, wafers are grouped as a lot to go through repeated sequences of operations to build circuitry. Lot scheduling is an important task for manufacturers in order to improve production efficiency and satisfy customers’ demands of on-time delivery. Cycle time and average work-in-process reduction while meeting customers’ requirements play an important role in improving the competitiveness and sustainability of a semiconductor manufacturer. In this research, we propose the optimal combination rules for lot scheduling problems in wafer fabs, focusing on three complex areas of decision making: lot release control, batch sizing, and dispatching lots to enhance competitiveness and sustainability of a semiconductor facility.

  14. Semiconductor technologies in the era of electronics

    CERN Document Server

    Kang, Yong Hoon

    2014-01-01

    Technological advances in the field of materials, devices, circuits, and systems began by the discovery of new properties of objects, or the entrepreneurship with the applications of unique or practical concepts for commercial goods. To implement products using these findings and challenges textbook knowledge is usually sufficient. Semiconductor Technologies in the Era of Electronics therefore does not aim to look deeper in certain areas but it offers a broad and comprehensive overview of the field to: - Experts of specific knowledge who want to expand the overall understanding to different areas - Persons who wish to understand the principle of electronic devices often seen in everyday life - Entrepreneurs interested in the innovations and changes of semiconductor technologies and overall electronics industry. A profound and theoretical approach is therefore used and special cases essential to understanding these important concept are presented.

  15. Semiconductor industry wafer fab exhaust management

    CERN Document Server

    Sherer, Michael J

    2005-01-01

    Given the myriad exhaust compounds and the corresponding problems that they can pose in an exhaust management system, the proper choice of such systems is a complex task. Presenting the fundamentals, technical details, and general solutions to real-world problems, Semiconductor Industry: Wafer Fab Exhaust Management offers practical guidance on selecting an appropriate system for a given application. Using examples that provide a clear understanding of the concepts discussed, Sherer covers facility layout, support facilities operations, and semiconductor process equipment, followed by exhaust types and challenges. He reviews exhaust point-of-use devices and exhaust line requirements needed between process equipment and the centralized exhaust system. The book includes information on wet scrubbers for a centralized acid exhaust system and a centralized ammonia exhaust system and on centralized equipment to control volatile organic compounds. It concludes with a chapter devoted to emergency releases and a separ...

  16. Fundamentals of semiconductor manufacturing and process control

    CERN Document Server

    May, Gary S

    2006-01-01

    A practical guide to semiconductor manufacturing from process control to yield modeling and experimental design Fundamentals of Semiconductor Manufacturing and Process Control covers all issues involved in manufacturing microelectronic devices and circuits, including fabrication sequences, process control, experimental design, process modeling, yield modeling, and CIM/CAM systems. Readers are introduced to both the theory and practice of all basic manufacturing concepts. Following an overview of manufacturing and technology, the text explores process monitoring methods, including those that focus on product wafers and those that focus on the equipment used to produce wafers. Next, the text sets forth some fundamentals of statistics and yield modeling, which set the foundation for a detailed discussion of how statistical process control is used to analyze quality and improve yields. The discussion of statistical experimental design offers readers a powerful approach for systematically varying controllable p...

  17. Epitaxy of Semiconductors Introduction to Physical Principles

    CERN Document Server

    Pohl, Udo W

    2013-01-01

    Introduction to Epitaxy provides the essential information for a comprehensive upper-level graduate course treating the crystalline growth of semiconductor heterostructures. Heteroepitaxy represents the basis of advanced electronic and optoelectronic devices today and is considered one of the top fields in materials research. The book covers the structural and electronic properties of strained epitaxial layers, the thermodynamics and kinetics of layer growth, and the description of the major growth techniques metalorganic vapor phase epitaxy, molecular beam epitaxy and liquid phase epitaxy. Cubic semiconductors, strain relaxation by misfit dislocations, strain and confinement effects on electronic states, surface structures and processes during nucleation and growth are treated in detail. The Introduction to Epitaxy requires only little knowledge on solid-state physics. Students of natural sciences, materials science and electrical engineering as well as their lecturers benefit from elementary introductions t...

  18. Artificial Photosynthesis with Semiconductor-Liquid Junctions.

    Science.gov (United States)

    Guijarro, Néstor; Formal, Florian Le; Sivula, Kevin

    2015-02-25

    Given the urgent need to develop a sustainable, carbon neutral energy storage system on a global scale, intense efforts are currently underway to advance the field of artificial photosynthesis: i.e. solar fuel engineering. In this review we give an overview of the field of artificial photosynthesis using a semiconductor-electrolyte interface employed in a photoelectrochemical device or as a heterogeneous photocatalyst. First we present a basic description of the operation principles of a semiconductor-liquid junction based device. The role of nanotechnology in the recent advances in the field is highlighted and common material systems under current study are briefly reviewed. The importance of the material surfaces are further scrutinized by presenting recent advances in interfacial engineering. Technical challenges and an outlook towards industrialization of the technology are given.

  19. New materials for radiation hard semiconductor detectors

    CERN Document Server

    Sellin, P J; CERN. Geneva

    2006-01-01

    We present a review of the current status of research into new semiconductor materials for use as particle tracking detectors in very high radiation environments. This work is carried out within the framework of the CERN RD50 collaboration, which is investigating detector technologies suitable for operation at the proposed Super-LHC facility (SLHC). Tracking detectors operating at the SLHC in this environment will have to be capable of withstanding radiation levels arising from a luminosity of 1035 cm-2s-1 which will present severe challenges to current tracking detector technologies. The "new materials" activity within RD50 is investigating the performance of various semiconductor materials that potentially offer radiation hard alternatives to silicon devices. The main contenders in this study are silicon carbide, gallium nitride and amorphous silicon. In this paper we review the current status of these materials, in terms of material quality, commercial availability, charge transport properties, and radiati...

  20. Large Bandgap Semiconductors for Solar Water Splitting

    DEFF Research Database (Denmark)

    Malizia, Mauro

    Photoelectrochemical water splitting represents an eco-friendly technology that could enable the production of hydrogen using water as reactant and solar energy as primary energy source. The exploitation of solar energy for the production of hydrogen would help modern society to reduce the reliance...... water splitting devices having tandem design. The increase of the photovoltage produced by GaP under illumination was the main goal of this work. GaP has a bandgap of 2.25 eV and could in theory produce a photovoltage of approximately 1.7 V. Instead, the photovoltage produced by the semiconductor...... (bismuth vanadate) was investigated in view of combining this 2.4 eV large bandgap semiconductor with a Si back-illuminated photocathode. A device obtained by mechanical stacking of BiVO4 photoanode and standard Si photocathode performs non-assisted water splitting under illumination with Solar...

  1. Lattice Location of Transition Metals in Semiconductors

    CERN Multimedia

    2002-01-01

    %IS366 %title\\\\ \\\\Transition metals (TMs) in semiconductors have been the subject of considerable research for nearly 40 years. This is due both to their role as important model impurities for deep centers in semiconductors, and to their technological impact as widespread contaminants in Si processing, where the miniaturization of devices requires to keep their sheet concentration below 10$^{10}$ cm$^{-2}$. As a consequence of the low TM solubility, conventional ion beam methods for direct lattice location have failed completely in identifying the lattice sites of isolated transition metals. Although electron paramagnetic resonance (EPR) has yielded valuable information on a variety of TM centers, it has been unable to detect certain defects considered by theory, e.g., isolated interstitial or substitutional Cu in Si. The proposed identity of other EPR centers such as substitutional Fe in Si, still needs confirmation by additional experimental methods. As a consequence, the knowledge on the structural propert...

  2. Liquid Crystalline Semiconductors Materials, properties and applications

    CERN Document Server

    Kelly, Stephen; O'Neill, Mary

    2013-01-01

    This is an exciting stage in the development of organic electronics. It is no longer an area of purely academic interest as increasingly real applications are being developed, some of which are beginning to come on-stream. Areas that have already been commercially developed or which are under intensive development include organic light emitting diodes (for flat panel displays and solid state lighting), organic photovoltaic cells, organic thin film transistors (for smart tags and flat panel displays) and sensors. Within the family of organic electronic materials, liquid crystals are relative newcomers. The first electronically conducting liquid crystals were reported in 1988 but already a substantial literature has developed. The advantage of liquid crystalline semiconductors is that they have the easy processability of amorphous and polymeric semiconductors but they usually have higher charge carrier mobilities. Their mobilities do not reach the levels seen in crystalline organics but they circumvent all of t...

  3. Hot carrier degradation in semiconductor devices

    CERN Document Server

    2015-01-01

    This book provides readers with a variety of tools to address the challenges posed by hot carrier degradation, one of today’s most complicated reliability issues in semiconductor devices.  Coverage includes an explanation of carrier transport within devices and book-keeping of how they acquire energy (“become hot”), interaction of an ensemble of colder and hotter carriers with defect precursors, which eventually leads to the creation of a defect, and a description of how these defects interact with the device, degrading its performance. • Describes the intricacies of hot carrier degradation in modern semiconductor technologies; • Covers the entire hot carrier degradation phenomenon, including topics such as characterization, carrier transport, carrier-defect interaction, technological impact, circuit impact, etc.; • Enables detailed understanding of carrier transport, interaction of the carrier ensemble with the defect precursors, and an accurate assessment of how the newly created defects imp...

  4. Theory of radiation disordering and annealing semiconductors

    Science.gov (United States)

    Oksengendler, B. L.; Turaeva, N. N.

    A new model of radiation disordering of semiconductors is proposed. According to this model, disordering clusters capable of self-annealing are stabilized by auto-localized electronic excitations (electrons, holes and excitons). Impulse annealing of this medium takes place if the electron stoppers are annihilated so that the disordered clusters emerge. This model is in accordance with experimental data of amorphization and impulse annealing.

  5. Metastable states in amorphous chalcogenide semiconductors

    CERN Document Server

    Mikla, Victor I

    2009-01-01

    This book addresses an interesting and technologically important class of materials, the amorphous chalcogenide semiconductors. Experimental results on the structural and electronic metastable states in Se-rich chalcogenides are presented. Special attention is paid to the states in the mobility gap and their sensitivity to various factors such as irradiation, annealing and composition. Photoinduced changes of structure and physical properties are also considered and structural transformation at photocrystallization is studied in detail. Finally, the authors discuss potential applications of th

  6. Semiconductor Sensors for a Wide Temperature Range

    OpenAIRE

    Nikolay GORBACHUK; Mikhail LARIONOV; Aleksey FIRSOV; Nikolay SHATIL

    2014-01-01

    Prototype sensors are described that are applicable for pressure, position, temperature, and field measurements in the temperature range of 4.2 to 300 K. The strain gauges utilize the silicon substrate and thin film technology. The tensosensitivity of strain sensors is 40 µV/mln-1 or better depending on metrological characteristics of semiconductor films, orientation, and current. The temperature sensors (thermistors) make use of the germanium powder bulk. The temperature coefficient of resis...

  7. Semiconductor physics at WIT and Trinity College

    OpenAIRE

    O'Raifeartaigh, Cormac

    2006-01-01

    A WIT research group that studies the physics of semiconductors is coordinated by Dr. Cormac O’Raifeartaigh of the School of Science. Experimental research is carried out at the electron spin resonance (ESR) laboratory at Trinity College Dublin (TCD) in collaboration with Dr. Robert Barklie of TCD. Research data are analysed at WIT with theoretical support provided by Dr. Mohammad Alhourani and Mr. Frank Leonard. The group has participated in research projects funded by WIT (BEHEST Programme)...

  8. The quantum Boltzmann equation in semiconductor physics

    Energy Technology Data Exchange (ETDEWEB)

    Snoke, D.W. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260 (United States)

    2011-01-15

    The quantum Boltzmann equation, or Fokker-Planck equation, has been used to successfully explain a number of experiments in semiconductor optics in the past two decades. This paper reviews some of the developments of this work, including models of excitons in bulk materials, electron-hole plasmas, and polariton gases. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. The physics and applications of amorphous semiconductors

    CERN Document Server

    Madan, Arun

    1988-01-01

    This comprehensive, detailed treatise on the physics and applications of the new emerging technology of amorphous semiconductors focuses on specific device research problems such as the optimization of device performance. The first part of the book presents hydrogenated amorphous silicon type alloys, whose applications include inexpensive solar cells, thin film transistors, image scanners, electrophotography, optical recording and gas sensors. The second part of the book discusses amorphous chalcogenides, whose applications include electrophotography, switching, and memory elements. This boo

  10. Exciton-polariton wakefields in semiconductor microcavities

    Energy Technology Data Exchange (ETDEWEB)

    Terças, H., E-mail: hugo.tercas@uibk.ac.at [Physics of Information Group, Instituto de Telecomunicações, Lisbon (Portugal); Institute for Theoretical Physics, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck (Austria); Mendonça, J.T., E-mail: titomend@ist.utl.pt [Instituto de Física, Universidade de São Paulo, São Paulo SP, 05508-090 Brazil (Brazil); IPFN, Instituto Superior Técnico, 1049-001 Lisboa (Portugal)

    2016-02-22

    We consider the excitation of polariton wakefields due to a propagating light pulse in a semiconductor microcavity. We show that two kinds of wakes are possible, depending on the constituents fraction (either exciton or photon) of the polariton wavefunction. The nature of the wakefields (pure excitonic or polaritonic) can be controlled by changing the speed of propagation of the external pump. This process could be used as a diagnostic for the internal parameters of the microcavity.

  11. Semiconductor plasmonic nanolasers: current status and perspectives.

    Science.gov (United States)

    Gwo, Shangjr; Shih, Chih-Kang

    2016-08-01

    Scaling down semiconductor lasers in all three dimensions holds the key to the development of compact, low-threshold, and ultrafast coherent light sources, as well as integrated optoelectronic and plasmonic circuits. However, the minimum size of conventional semiconductor lasers utilizing dielectric cavity resonators (photonic cavities) is limited by the diffraction limit. To date, surface plasmon amplification by stimulated emission of radiation (spaser)-based plasmonic nanolaser is the only photon and plasmon-emitting device capable of this remarkable feat. Specifically, it has been experimentally demonstrated that the use of plasmonic cavities based on metal-insulator-semiconductor (MIS) nanostructures can indeed break the diffraction limit in all three dimensions. In this review, we present an updated overview of the current status for plasmonic nanolasers using the MIS configuration and other related metal-cladded semiconductor microlasers. In particular, by using composition-varied indium gallium nitride/gallium nitride core-shell nanorods, it is possible to realize all-color, single-mode nanolasers in the full visible wavelength range with ultralow continuous-wave (CW) lasing thresholds. The lasing action in these subdiffraction plasmonic cavities is achieved via a unique auto-tuning mechanism based on the property of weak size dependence inherent in plasmonic nanolasers. As for the choice of metals in the plasmonic structures, epitaxial silver films and giant colloidal silver crystals have been shown to be the superior constituent materials for plasmonic cavities due to their low plasmonic losses in the visible and near-infrared (NIR) spectral regions. In this review, we also provide some perspectives on the challenges and opportunities in this exciting new research frontier.

  12. Reduced filamentation in high power semiconductor lasers

    DEFF Research Database (Denmark)

    Skovgaard, Peter M. W.; McInerney, John; O'Brien, Peter

    1999-01-01

    High brightness semiconductor lasers have applications in fields ranging from material processing to medicine. The main difficulty associated with high brightness is that high optical power densities cause damage to the laser facet and thus require large apertures. This, in turn, results in spatio....... Experimentally, we generate transverse current profiles by using standard lithography to define a digitated contact pad. Experimental results confirm that the current density is significantly altered and show completely filamentation-free operation up to 34 times threshold....

  13. GaTe semiconductor for radiation detection

    Science.gov (United States)

    Payne, Stephen A [Castro Valley, CA; Burger, Arnold [Nashville, TN; Mandal, Krishna C [Ashland, MA

    2009-06-23

    GaTe semiconductor is used as a room-temperature radiation detector. GaTe has useful properties for radiation detectors: ideal bandgap, favorable mobilities, low melting point (no evaporation), non-hygroscopic nature, and availability of high-purity starting materials. The detector can be used, e.g., for detection of illicit nuclear weapons and radiological dispersed devices at ports of entry, in cities, and off shore and for determination of medical isotopes present in a patient.

  14. Determination of Insulator-to-Semiconductor Transition in Sol-Gel Oxide Semiconductors Using Derivative Spectroscopy

    Directory of Open Access Journals (Sweden)

    Woobin Lee

    2015-12-01

    Full Text Available We report a derivative spectroscopic method for determining insulator-to-semiconductor transition during sol-gel metal-oxide semiconductor formation. When an as-spun sol-gel precursor film is photochemically activated and changes to semiconducting state, the light absorption characteristics of the metal-oxide film is considerable changed particularly in the ultraviolet region. As a result, a peak is generated in the first-order derivatives of light absorption (A′ vs. wavelength (λ plots, and by tracing the peak center shift and peak intensity, transition from insulating-to-semiconducting state of the film can be monitored. The peak generation and peak center shift are described based on photon-energy-dependent absorption coefficient of metal-oxide films. We discuss detailed analysis method for metal-oxide semiconductor films and its application in thin-film transistor fabrication. We believe this derivative spectroscopy based determination can be beneficial for a non-destructive and a rapid monitoring of the insulator-to-semiconductor transition in sol-gel oxide semiconductor formation.

  15. Semiconductor type dependent role of metal nanoparticle in metal and semiconductor nanostructured junction.

    Science.gov (United States)

    Lee, Seung-Hoon; Jang, Jae-Won

    Among hybrid nanostructures, semiconductor with metal nanomaterial has been more exploited because metal and semiconductor have different properties that, in combination, result in unique electrical and optical properties. Localized surface plasmon resonance (LSPR), which is one of novel properties of metal nanoparticles (NPs), has been used as a good strategy for increasing an opto-electric performance in semiconductors. In this presentation, improvement of the opto-electronic properties of non-single crystallized nanowire (NW) devices with space charges generated by LSPR is demonstrated. The photocurrent and spectral response of single polypyrrole (PPy) NW devices are increased by electrostatically attached Ag NPs. In particular, it is also proved the space charge generation by LSPR of Ag NPs by means of characterizing current-voltage (J-V) dependence and finite differential time domain (FDTD) simulation on the NW devices. Moreover, semiconductor type dependent role of metal NP in metal NPs decorated semiconductor NW is demonstrated by using light irradiated Kevin probe force microscopy. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2015R1A1A1A05027681 and NRF-2016K1A3A1A32913212).

  16. Defect Tolerant Semiconductors for Solar Energy Conversion.

    Science.gov (United States)

    Zakutayev, Andriy; Caskey, Christopher M; Fioretti, Angela N; Ginley, David S; Vidal, Julien; Stevanovic, Vladan; Tea, Eric; Lany, Stephan

    2014-04-03

    Defect tolerance is the tendency of a semiconductor to keep its properties despite the presence of crystallographic defects. Scientific understanding of the origin of defect tolerance is currently missing. Here we show that semiconductors with antibonding states at the top of the valence band are likely to be tolerant to defects. Theoretical calculations demonstrate that Cu3N with antibonding valence band maximum has shallow intrinsic defects and no surface states, in contrast to GaN with bonding valence band maximum. Experimental measurements indicate shallow native donors and acceptors in Cu3N thin films, leading to 10(16)-10(17) cm(-3) doping with either electrons or holes depending on the growth conditions. The experimentally measured bipolar doping and the solar-matched optical absorption onset (1.4 eV) make Cu3N a promising candidate absorber for photovoltaic and photoelectrochemical solar cells, despite the calculated indirect fundamental band gap (1.0 eV). These conclusions can be extended to other materials with antibonding character of the valence band, defining a class of defect-tolerant semiconductors for solar energy conversion applications.

  17. Photoelectrolysis Using Type-II Semiconductor Heterojunctions.

    Science.gov (United States)

    Harrison, S; Hayne, M

    2017-09-14

    The solar-powered production of hydrogen for use as a renewable fuel is highly desirable for the world's future energy infrastructure. However, difficulties in achieving reasonable efficiencies, and thus cost-effectiveness, have hampered significant research progress. Here we propose the use of semiconductor nanostructures to create a type-II heterojunction at the semiconductor-water interface in a photoelectrochemical cell (PEC) and theoretically investigate it as a method of increasing the maximum photovoltage such a cell can generate under illumination, with the aim of increasing the overall cell efficiency. A model for the semiconductor electrode in a PEC is created, which solves the Schrödinger, Poisson and drift-diffusion equations self-consistently. From this, it is determined that ZnO quantum dots on bulk n-InGaN with low In content x is the most desirable system, having electron-accepting and -donating states straddling the oxygen- and hydrogen-production potentials for x < 0.26, though large variance in literature values for certain material parameters means large uncertainties in the model output. Accordingly, results presented here should form the basis for further experimental work, which will in turn provide input to refine and develop the model.

  18. Transparent Oxide Semiconductors for Emerging Electronics

    KAUST Repository

    Caraveo-Frescas, Jesus Alfonso

    2013-11-01

    Transparent oxide electronics have emerged as promising materials to shape the future of electronics. While several n-type oxides have been already studied and demonstrated feasibility to be used as active materials in thin film transistors, high performance p-type oxides have remained elusive. This dissertation is devoted to the study of transparent p-type oxide semiconductor tin monoxide and its use in the fabrication of field effect devices. A complete study on the deposition of tin monoxide thin films by direct current reactive magnetron sputtering is performed. Carrier density, carrier mobility and conductivity are studied over a set of deposition conditions where p-type conduction is observed. Density functional theory simulations are performed in order to elucidate the effect of native defects on carrier mobility. The findings on the electrical properties of SnO thin films are then translated to the fabrication of thin films transistors. The low processing temperature of tin monoxide thin films below 200 oC is shown advantageous for the fabrication of fully transparent and flexible thin film transistors. After careful device engineering, including post deposition annealing temperature, gate dielectric material, semiconductor thickness and source and drain electrodes material, thin film transistors with record device performance are demonstrated, achieving a field effect mobility >6.7 cm2V-1s-1. Device performance is further improved to reach a field effect mobility of 10.8 cm2V-1s-1 in SnO nanowire field effect transistors fabricated from the sputtered SnO thin films and patterned by electron beam lithography. Downscaling device dimension to nano scale is shown beneficial for SnO field effect devices not only by achieving a higher hole mobility but enhancing the overall device performance including better threshold voltage, subthreshold swing and lower number of interfacial defects. Use of p-type semiconductors in nonvolatile memory applications is then

  19. Solution combustion synthesis of oxide semiconductors

    Science.gov (United States)

    Thomas, Abegayl Lorenda Shara-Lynn

    The quest for stable and efficient photocatalytic materials beyond TiO2 and WO3 has over the years led to the development of new materials that possess varied interfacial energetics. This dissertation study focused on using for the first time a novel method, solution combustion synthesis (SCS), to prepare two distinct families of binary metal-based oxide semiconductor materials. Detailed studies on material characteristics and applications were carried out on tungsten- and niobium-based oxide semiconductors with varying principal metals. Initial emphasis was placed on the SCS of tungsten-based oxide semiconductors (ZnWO4, CuWO4, and Ag2WO4). The influence of different tungsten precursor's on the resultant product was of particular relevance to this study, with the most significant effects highlighted. Upon characterization, each sample's photocatalytic activity towards methyl orange dye degradation was studied, and benchmarked against their respective commercial oxide sample, obtained by solid-state ceramic synthesis. Detailed analysis highlighted the importance of the SCS process as a time- and energy-efficient method to produce crystalline nano-sized materials even without additional or excessive heat treatment. It was observed that using different tungstate precursors does influence the structural and morphological make-up of the resulting materials. The as-synthesized tungstate materials showed good photocatalytic performance for the degradation of methyl orange dye, while taking into account specific surface area and adsorbed dye amount on the surface of the material. Like the tungstate's, niobium-based oxide semiconductors CuNb 2O6 and ZnNb2O6 were the first to be synthesized via solution combustion synthesis. Particular attention was placed on the crystal structures formed while using an oxalate niobium precursor during the reaction process. X-ray patterns yielded a multiphase structure for the ZnNb2O6 and a single phase structure for CuNb 2O6

  20. Review of wide band-gap semiconductors technology

    Directory of Open Access Journals (Sweden)

    Jin Haiwei

    2016-01-01

    Full Text Available Silicon carbide (SiC and gallium nitride (GaN are typical representative of the wide band-gap semiconductor material, which is also known as third-generation semiconductor materials. Compared with the conventional semiconductor silicon (Si or gallium arsenide (GaAs, wide band-gap semiconductor has the wide band gap, high saturated drift velocity, high critical breakdown field and other advantages; it is a highly desirable semiconductor material applied under the case of high-power, high-temperature, high-frequency, anti-radiation environment. These advantages of wide band-gap devices make them a hot spot of semiconductor technology research in various countries. This article describes the research agenda of United States and European in this area, focusing on the recent developments of the wide band-gap technology in the US and Europe, summed up the facing challenge of the wide band-gap technology.

  1. Synthesis and characterization of metal/semiconductor nanocomposites for photocatalysis

    OpenAIRE

    Mavrič, Tina

    2017-01-01

    The doctoral dissertation focused on improving photocatalytic activity of nanopowdered ZnO by constructing I) Metal-Semiconductor and II) Semiconductor-Semiconductor heterostructures. Both heterostructure types have been reported to have a beneficial effect on photocatalytic efficiency. For the first part (I) Ag/ZnO nanocomposite was synthesized. Here we investigated an influence of polyvinylpyrrolidone (PVP) addition during the synthesis on the particle properties and their photoactivity. Th...

  2. Semiconductor diode characterization for total skin electron irradiation.

    Science.gov (United States)

    Madrid González, O A; Rivera Montalvo, T

    2014-01-01

    In this paper, a semiconductor diode characterization was performed. The diode characterization was completed using an electron beam with 4 MeV of energy. The semiconductor diode calibration used irradiation with an electron beam in an ion chamber. "In vivo" dosimetry was also conducted. The dosimetry results revealed that the semiconductor diode was a good candidate for use in the total skin electron therapy (TSET) treatment control. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. Graded core/shell semiconductor nanorods and nanorod barcodes

    Science.gov (United States)

    Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

    2010-12-14

    Graded core/shell semiconductor nanorods and shaped nanorods are disclosed comprising Group II-VI, Group III-V and Group IV semiconductors and methods of making the same. Also disclosed are nanorod barcodes using core/shell nanorods where the core is a semiconductor or metal material, and with or without a shell. Methods of labeling analytes using the nanorod barcodes are also disclosed.

  4. Methods and devices for fabricating and assembling printable semiconductor elements

    Energy Technology Data Exchange (ETDEWEB)

    Nuzzo, Ralph G.; Rogers, John A.; Menard, Etienne; Lee, Keon Jae; Khang, Dahl-Young; Sun, Yugang; Meitl, Matthew; Zhu, Zhengtao

    2017-09-19

    The invention provides methods and devices for fabricating printable semiconductor elements and assembling printable semiconductor elements onto substrate surfaces. Methods, devices and device components of the present invention are capable of generating a wide range of flexible electronic and optoelectronic devices and arrays of devices on substrates comprising polymeric materials. The present invention also provides stretchable semiconductor structures and stretchable electronic devices capable of good performance in stretched configurations.

  5. Electrically-Generated Spin Polarization in Non-Magnetic Semiconductors

    Science.gov (United States)

    2016-03-31

    AFRL-AFOSR-VA-TR-2016-0143 Electrically-generated spin polarization in non -magnetic semiconductors Vanessa Sih UNIVERSITY OF MICHIGAN Final Report 03...SUBTITLE (YIP) - Electrically-generated spin polarization in non -magnetic semiconductors 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-12-1-0258 5c...that produced electrically-generated electron spin polarization in non -magnetic semiconductor heterostructures. Electrically-generated electron spin

  6. Ultrafast Degenerate Transient Lens Spectroscopy in Semiconductor Nanosctructures

    Directory of Open Access Journals (Sweden)

    Leontyev A.V.

    2015-01-01

    Full Text Available We report the non-resonant excitation and probing of the nonlinear refractive index change in bulk semiconductors and semiconductor quantum dots through degenerate transient lens spectroscopy. The signal oscillates at the center laser field frequency, and the envelope of the former in quantum dots is distinctly different from the one in bulk sample. We discuss the applicability of this technique for polarization state probing in semiconductor media with femtosecond temporal resolution.

  7. Quantum Dot Semiconductor Optical Amplifiers - Physics and Applications

    OpenAIRE

    Berg, Tommy Winther; Mørk, Jesper

    2004-01-01

    This thesis describes the physics and applications of quantum dot semiconductor optical amplifiers based on numerical simulations. These devices possess a number of unique properties compared with other types of semiconductor amplifiers, which should allow enhanced performance of semiconductor devices in communication systems in the future. The basic properties of quantum dot devices are investigated, especially regarding the potential of realizing amplification and signal processing without ...

  8. Physics and chemistry of III-V compound semiconductor interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wilmsen, C.W.

    1985-01-01

    This book brings together fundamental and practical knowledge on the physics and chemistry of the III-V compounds with metals and dielectrics. The authors provide concise overviews of these areas with many tables and graphs which compare and summarize the literature. The major divisions of the book cover semiconductor surface interactions, Schottky diodes and ohmic contacts, the deposited insulator, electrical properties of insulator-semiconductor interfaces, inversion layer transport, interfacial constraints on MIS devices, and oxide semiconductor interfaces.

  9. Methods and devices for fabricating and assembling printable semiconductor elements

    Science.gov (United States)

    Nuzzo, Ralph G; Rogers, John A; Menard, Etienne; Lee, Keon Jae; Khang, Dahl-Young; Sun, Yugang; Meitl, Matthew; Zhu, Zhengtao

    2013-05-14

    The invention provides methods and devices for fabricating printable semiconductor elements and assembling printable semiconductor elements onto substrate surfaces. Methods, devices and device components of the present invention are capable of generating a wide range of flexible electronic and optoelectronic devices and arrays of devices on substrates comprising polymeric materials. The present invention also provides stretchable semiconductor structures and stretchable electronic devices capable of good performance in stretched configurations.

  10. Revised diode equation for Ideal Graphene-Semiconductor Schottky Junction

    OpenAIRE

    Liang, Shi-Jun; Ang, Lay Kee

    2015-01-01

    In this paper we carry out a theoretical and experimental study of the nature of graphene/semiconductor Schottky contact. We present a simple and parameter-free carrier transport model of graphene/semiconductor Schottky contact derived from quantum statistical theory, which is validated by the quantum Landauer theory and first-principle calculations. The proposed model can well explain experimental results for samples of different types of graphene/semiconductor Schottky contact.

  11. Transistor electronics use of semiconductor components in switching operations

    CERN Document Server

    Rumpf, Karl-Heinz

    2014-01-01

    Transistor Electronics: Use of Semiconductor Components in Switching Operations presents the semiconductor components as well as their elementary circuits. This book discusses the scope of application of electronic devices to increase productivity. Organized into eight chapters, this book begins with an overview of the general equation for the representation of integer positive numbers. This text then examines the properties and characteristics of basic electronic components, which relates to an understanding of the operation of semiconductors. Other chapters consider the electronic circuit ar

  12. Methods and devices for fabricating and assembling printable semiconductor elements

    Energy Technology Data Exchange (ETDEWEB)

    Nuzzo, Ralph G.; Rogers, John A.; Menard, Etienne; Lee, Keon Jae; Khang, Dahl-Young; Sun, Yugang; Meitl, Matthew; Zhu, Zhengtao

    2017-09-12

    The invention provides methods and devices for fabricating printable semiconductor elements and assembling printable semiconductor elements onto substrate surfaces. Methods, devices and device components of the present invention are capable of generating a wide range of flexible electronic and optoelectronic devices and arrays of devices on substrates comprising polymeric materials. The present invention also provides stretchable semiconductor structures and stretchable electronic devices capable of good performance in stretched configurations.

  13. Fabrication and Characterization of Edge-Emitting Semiconductor Lasers

    Science.gov (United States)

    Song, Junyeob

    The semiconductor laser was invented in 1962, and has recently become ubiquitous in modern life. This thesis focuses on the development of a semiconductor laser fabricating process which utilizes semiconductor manufacturing technology in a cleanroom environment including photolithography, etching, deposition, and bonding processes. A photomask for patterning is designed, recipes of photolithography process and etching process are developed with experiments. This work gives how to develop the process of fabrication and determine the parameters for each processes. A series of semiconductor laser devices are then fabricated using the developed process and characterization is performed to assess device performance with industrial standard methods. A fabricated device has 18W power and 11% conversion efficiency.

  14. Hard gap in epitaxial semiconductor-superconductor nanowires

    DEFF Research Database (Denmark)

    Chang, W.; Albrecht, S. M.; Jespersen, T. S.

    2015-01-01

    information processing. Proposals in this direction based on proximity effect in semiconductor nanowires are appealing because the key ingredients are currently in hand. However, previous instances of proximitized semiconductors show significant tunneling conductance below the superconducting gap, suggesting...... a continuum of subgap states---a situation that nullifies topological protection. Here, we report a hard superconducting gap induced by proximity effect in a semiconductor, using epitaxial Al-InAs superconductor-semiconductor nanowires. The hard gap, along with favorable material properties and gate...

  15. The charge state of hydrogen ions in metals and semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bazhukov, S.I.; Kibardin, A.V.; Pyatkova, T.M.; Urmanov, A.R. (Urals Polytechnical Inst., Sverdlovsk (USSR))

    1991-06-01

    The charge state of hydrogen ions in metals and semiconductors has been studied based on a comparison of hydrogen ion stopping cross-sections in metal and semiconductor targets. It is shown that neutralization of the hydrogen ion in metals and semiconductors at ion speeds v{sub i} {proportional to} (1-2)v{sub 0}, where v{sub 0} = 2.2x10{sup 8} cm/s, is due to different mechanisms, i.e. to a bulk effect in metals and to a subsurface effect in semiconductors. (orig.).

  16. Capacitance of semiconductor-electrolyte junction and its frequency dependence

    Science.gov (United States)

    Wang, Y.-B.; Yuan, R.-K.; Willander, M.

    1996-11-01

    The frequency dependent capacitance of semiconductor-electrolyte junction and its relationship to the surface roughness of the semiconductor and the ions in the electrolyte are discussed. Due to very low mobility of the ions, the observed capacitance can be dominated by the Helmholtz double-layer of the electrolyte rather than the space charge layer of the semiconductor. The capacitance will also depend on the frequency. This, often observed power-law frequency dependence of capacitance is ascribed to the contribution of constant phase angle impedance. The power-law exponent can easily be related to the fractal dimension if the semiconductor surface can be described by fractal geometry.

  17. Squeezing in an injection-locked semiconductor laser

    Science.gov (United States)

    Inoue, S.; Machida, S.; Yamamoto, Y.; Ohzu, H.

    1993-09-01

    The intensity-noise properties of an injection-locked semiconductor laser were studied experimentally. The constant-current-driven semiconductor laser producing the amplitude-squeezed state whose intensity noise was reduced below the standard quantum limit (SQL) by 0.72 dB was injection-locked by an external master laser. The measured intensity-noise level of the injection-locked semiconductor laser was 0.91 dB below the SQL. This experimental result indicates that a phase-coherent amplitude-squeezed state or squeezed vacuum state together with a reference local oscillator wave can be generated directly by semiconductor laser systems.

  18. Shallow-Lever Centers in Semiconductors - Proceedings of the 7th International Conference

    Science.gov (United States)

    Ammerlaan, C. A. J.; Pajot, B.

    1997-04-01

    Epitaxial Si Films Grown at Very Low Temperature (≤ 200°C) * An Oxygen-Related 1-Platinum Shallow-Level Center in n- and p-Type Silicon * Excitonic Enhanced Optical Gain for Wide-Gap Laser Diodes Using Impurity States * Multistep Changes of Defect Electrical Activity Due to Interaction with Hydrogen * Annealing Behavior of Crystalline Silicon Heavily Implanted with Oxygen at Low Temperature * Intracenter Population Inversion of Strain-Split Acceptor Levels in Ge * Field Ionization of Shallow Impurities at Random Potential * Magnetoluminescence Spectra Associated to Acceptors in GaAs-(Ga, Al)As Superlattices * Magnetic-Field Effects on the Optical Absorption Spectra Associated with Shallow Impurities in Quantum Wells * Shallow Level Excitations of Transition Metal and Rare Earth Element Isoelectronic Impurities in II-VI and III-V Semiconductors * Local States Band Induced by B-Delta Doping in Si/SiGe/Si Quantum Wells * Selfinterstitial and Selfinterstitial-Related Defects in Irradiated p-Type Silicon * Luminescence of Excitons Bound to Complexes of Impurities and Defects in Irradiated Germanium * On the Role of Closely Placed Excited States in the Anomalous Behaviour of the Spin System Fe3+ in GaAs * Optical Studies of Be Acceptors Confined in Flat Islands at GaAs/GaAlAs Quantum-Well Interfaces * Ab Initio Study of Group V Elements in Amorphous Silicon * Influence of Intrinsic Defects and S Substitutions on Electrical Properties of Chalcopyrite CuInS2 Compounds * Piezospectroscopy of Antimony in Germanium * Impurity Centre in a Single Quantum Well in the Presence of a Strong Magnetic Field * Electron Paramagnetic Resonance Study of a High Concentration Shallow Level Pt Defect in Silicon with Effective Mass Like Properties * Theory of Hydrogen Single Passivated Substitutional Sulphur Double Donor in Si * Diffusion of Cadmium into Gallium Arsenide Investigated by Means of SIMS and Spreading-Resistance Profiling * Size Effect of Shallow Acceptor Impurities on Formation

  19. Synthesis and applications of heterostructured semiconductor nanocrystals

    Science.gov (United States)

    Khon, Elena

    Semiconductor nanocrystals (NCs) have been of great interest to researchers for several decades due to their unique optoelectronic properties. These nanoparticles are widely used for a variety of different applications. However, there are many unresolved issues that lower the efficiency and/or stability of devices which incorporate these NCs. Our research is dedicated to addressing these issues by identifying potential problems and resolving them, improving existing systems, generating new synthetic strategies, and/or building new devices. The general strategies for the synthesis of different nanocrystals were established in this work, one of which is the colloidal growth of gold domains onto CdS semiconductor nanocrystals. Control of shape and size was achieved simply by adjusting the temperature and the time of the reaction. Depending on the exact morphology of Au and CdS domains, fabricated nano-composites can undergo evaporation-induced self-assembly onto a substrate, which is very useful for building devices. CdS/Au heterostructures can assemble in two different ways: through end-to-end coupling of Au domains, resulting in the formation of one-dimensional chains; and via side-by-side packing of CdS nanorods, leading to the onset of two-dimensional superlattices. We investigated the nature of exciton-plasmon interactions in Au-tipped CdS nanorods using femtosecond transient absorption spectroscopy. The study demonstrated that the key optoelectronic properties of electrically coupled metal and semiconductor domains are significantly different from those observed in systems with weak inter-domain coupling. In particular, strongly-coupled nanocomposites promote mixing of electronic states at semiconductor-metal domain interfaces, which causes a significant suppression of both plasmon and exciton carrier excitations. Colloidal QDs are starting to replace organic molecules in many different applications, such as organic light emmiting diods (OLEDs), due to their

  20. Hydrogen local vibrational modes in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    McCluskey, Matthew D. [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-06-01

    Following, a review of experimental techniques, theory, and previous work, the results of local vibrational mode (LVM) spectroscopy on hydrogen-related complexes in several different semiconductors are discussed. Hydrogen is introduced either by annealing in a hydrogen ambient. exposure to a hydrogen plasma, or during growth. The hydrogen passivates donors and acceptors in semiconductors, forming neutral complexes. When deuterium is substituted for hydrogen. the frequency of the LVM decreases by approximately the square root of two. By varying the temperature and pressure of the samples, the microscopic structures of hydrogen-related complexes are determined. For group II acceptor-hydrogen complexes in GaAs, InP, and GaP, hydrogen binds to the host anion in a bond-centered orientation, along the [111] direction, adjacent to the acceptor. The temperature dependent shift of the LVMs are proportional to the lattice thermal energy U(T), a consequence of anharmonic coupling between the LVM and acoustical phonons. In the wide band gap semiconductor ZnSe, epilayers grown by metalorganic chemical vapor phase epitaxy (MOCVD) and doped with As form As-H complexes. The hydrogen assumes a bond-centered orientation, adjacent to a host Zn. In AlSb, the DX centers Se and Te are passivated by hydrogen. The second, third, and fourth harmonics of the wag modes are observed. Although the Se-D complex has only one stretch mode, the Se-H stretch mode splits into three peaks. The anomalous splitting is explained by a new interaction between the stretch LVM and multi-phonon modes of the lattice. As the temperature or pressure is varied, and anti-crossing is observed between LVM and phonon modes.

  1. Miniature thermoelectric coolers for semiconductor lasers

    Energy Technology Data Exchange (ETDEWEB)

    Semenyuk, V.A. [Odessa State Academy of Refrigeration, Odessa (Ukraine); Pilipenko, T.V. [EDO Corp./Barnes Engineering Division, 88 Long Hill Cross Rd., Shelton, Connecticut 06484 (United States); Albright, G.C.; Ioffe, L.A.; Rolls, W.H. [Odessa State Academy of Refrigeration, Odessa (Ukraine)

    1994-08-10

    The problem of matching thermoelectric coolers and semiconductor lasers with respect to heat flow densities and electrical currents is discussed. It is shown that the solution of this problem is accomplished by the reduction of thermoelement dimensions to the submillimeter level. Assembled with extruded thermoelectric materials, miniature coolers with a thermoelement length as short as 0.1 mm and a cross section of 0.2{times}0.2 mm{sup 2} are demonstrated. Using 0.5 mm thick aluminum ceramic plates, the overall height of these miniature coolers can be as low as 1.1 mm. The devices are designed for cooling and thermally stabilizing miniature optoelectronic elements, especially semiconductor lasers. The results of device testing over a wide range of temperature and heat loads are given. This novel approach in thermoelectric cooler design represents a new step in miniaturization and reduced current requirements, with little or no loss in maximum attainable temperature difference. A {Delta}{ital T}{sub max} of 68 K is demonstrated with input current of 200 mA. Due to the small thermoelement length, extremely large heat flow densities at cold junctions are practical (up to 100 W/cm{sup 2} at {Delta}{ital T}=0), making these devices ideal for heat intensive local sources such as injection laser diodes. Due to the extremely small sizes, these coolers have a high speed of response where a {Delta}{ital T} of 35 K in specimens with the thermoelement length of 0.1 mm is approximately 150 milliseconds. These micro coolers are ideal for use within the semiconductor device housing and under conditions where limitations of power, size, and electrical current predominate. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  2. Dynamic thermoelectricity in uniform bipolar semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Volovichev, I.N., E-mail: vin@ire.kharkov.ua

    2016-07-01

    The theory of the dynamic thermoelectric effect has been developed. The effect lies in an electric current flowing in a closed circuit that consists of a uniform bipolar semiconductor, in which a non-uniform temperature distribution in the form of the traveling wave is created. The calculations are performed for the one-dimensional model in the quasi-neutrality approximation. It was shown that the direct thermoelectric current prevails, despite the periodicity of the thermal excitation, the circuit homogeneity and the lack of rectifier properties of the semiconductor system. Several physical reasons underlining the dynamic thermoelectric effect are found. One of them is similar to the Dember photoelectric effect, its contribution to the current flowing is determined by the difference in the electron and hole mobilities, and is completely independent of the carrier Seebeck coefficients. The dependence of the thermoelectric short circuit current magnitude on the semiconductor parameters, as well as on the temperature wave amplitude, length and velocity is studied. It is shown that the magnitude of the thermoelectric current is proportional to the square of the temperature wave amplitude. The dependence of the thermoelectric short circuit current on the temperature wave length and velocity is the nonmonotonic function. The optimum values for the temperature wave length and velocity, at which the dynamic thermoelectric effect is the greatest, have been deduced. It is found that the thermoelectric short circuit current changes its direction with decreasing the temperature wave length under certain conditions. The prospects for the possible applications of the dynamic thermoelectric effect are also discussed.

  3. Modelling of dc characteristics for granular semiconductors

    Science.gov (United States)

    Varpula, Aapo; Sinkkonen, Juha; Novikov, Sergey

    2010-11-01

    The dc characteristics of granular n-type semiconductors are calculated analytically with the drift-diffusion theory. Electronic trapping at the grain boundaries (GBs) is taken into account. The use of quadratic and linear GB potential profiles in the calculation is compared. The analytical model is verified with numerical simulation performed by SILVACO ATLAS. The agreement between the analytical and numerical results is excellent in a large voltage range. The results show that electronic trapping at the GBs has a remarkable effect on the highly nonlinear I-V characteristics of the material.

  4. Shielding Electrostatic Fields in Polar Semiconductor Nanostructures

    Science.gov (United States)

    Hönig, G. M. O.; Westerkamp, S.; Hoffmann, A.; Callsen, G.

    2017-02-01

    Polar semiconductor materials enable a variety of classic and quantum-light sources, which are optimized continuously. However, one key problem—the inherent electric crystal polarization of such materials—remains unsolved and deteriorates the radiative exciton decay rate. We suggest a sequence of reverse interfaces to compensate these polarization effects, while the polar, natural crystal growth direction is maintained. Former research approaches, like growth on less-polar crystal planes or even the stabilization of unnatural phases, never reached industrial maturity. In contrast, our concept provides a way for the development of ultrafast devices based on established growth processes for polar materials, while the electric potential landscape becomes adjustable.

  5. Broad-band semiconductor optical amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Ding Ying [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)]. E-mail: yingding@red.semi.ac.cn; Kan Qiang [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Wang Junling [Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China); Pan Jiaoqing [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Zhou Fan [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Chen Weixi [School of Physics, Peking University, Beijing 100871 (China); Wang Wei [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2007-01-15

    Broad-band semiconductor optical amplifiers (SOAs) with different thicknesses and thin bulk tensile-strained active layers were fabricated and studied. Amplified spontaneous emission (ASE) spectra and gain spectra of SOAs were measured and analyzed at different CW biases. A maximal 3 dB ASE bandwidth of 136 nm ranging from 1480 to 1616 nm, and a 3 dB optical amplifier gain bandwidth of about 90 nm ranging from 1510 to 1600 nm, were obtained for the very thin bulk active SOA. Other SOAs characteristics such as saturation output power and polarization sensitivity were measured and compared.

  6. Semiconductors for room temperature nuclear detector applications

    CERN Document Server

    James, Ralph B

    1995-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The""Willardson and Beer""Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series.

  7. Semiconductor grade, solar silicon purification project

    Science.gov (United States)

    Ingle, W. M.; Rosler, R. R.; Thompson, S. W.; Chaney, R. E.

    1979-01-01

    Experimental apparatus and procedures used in the development of a 3-step SiF2(x) polymer transport purification process are described. Both S.S.M.S. and E.S. analysis demonstrated that major purification had occured and some samples were indistinguishable from semiconductor grade silicon (except possibly for phosphorus). Recent electrical analysis via crystal growth reveals that the product contains compensated phosphorus and boron. The low projected product cost and short energy payback time suggest that the economics of this process will result in a cost less than the goal of $10/Kg(1975 dollars). The process appears to be readily scalable to a major silicon purification facility.

  8. Photocatalytic semiconductor clusters for fuel production

    Energy Technology Data Exchange (ETDEWEB)

    Wilcoxon, J.P.; Bliss, D.E.; Martin, J.E. [and others

    1995-10-01

    High quality crystalline, monodisperse nanometer-size semiconductor clusters were successfully grown using an inverse micellar synthesis process and their optical and structural properties were studied. Among the materials studied were PbS, FeS{sub 2}, MoS{sub 2}, CdS and related compounds. The results demonstrated strong electronic quantum confinement effects and broad tailorability of the bandgaps with decreasing cluster size, features that are important for the potential use of these materials as photocatalysts for solar fuel production and solar detoxification. The highlights of the work are included in an Executive Summary.

  9. Introduction to Space Charge Effects in Semiconductors

    CERN Document Server

    Böer, Karl W

    2010-01-01

    This book is the most comprehensive one to describe the basics of space-charge effects in semiconductors, starting from basic principles to advanced application in semiconducting devices. It uses detailed analyses of the transport, Poisson, and continuity equations to demonstrate the behavior of the solution curves of the complete set of field and current distributions, along with quantitative descriptions of the relevant band models of typical pn-junction and Schottky barrier devices. It emphasizes the relevance to actual devices and sets these results apart from more simple models of networks of diodes and resistors. The book is especially important for people interested in detail analysis of solar cells and their efficiencies.

  10. Effect of gain nonlinearity in semiconductor lasers

    DEFF Research Database (Denmark)

    Jensen, Niels H.; Christiansen, Peter Leth; Skovgaard, Ove

    1988-01-01

    Semiconductor lasers are modeled by single-mode rate equations with Langevin noise terms and the influence of nonlinear gain is investigated. For cw operation the probability distribution for the carrier number and the photon number in the laser cavity is obtained. The corresponding (2......+1)-dimensional Fokker-Planck equation is derived and integrated on an Amdahl VP1100 vector processor. Above threshold the resulting probability density agrees with the rate-equation predictions. The case of high-speed modulation is also considered. The nonlinear gain is found to stabilize the laser....

  11. Current switching in superconductor semiconductor bilayers

    Science.gov (United States)

    Rahman, F.; Thornton, T. J.; Huber, R.

    2006-09-01

    We describe results of electrical transport experiments on niobium-on-indium arsenide and aluminium-on-indium arsenide bilayers. The temperature-dependent properties of electrical conduction in these bilayers is examined first in order to characterize the quality of super-semi interfaces. Next, we look at the differential resistance of the bilayers as a function of bias current. The switching of current between the metal and semiconductor components of the bilayer gives rise to a quasi-inductive effect as it causes voltage spikes in the composite system. Also described is the variation of critical current for these bilayers with temperature and magnetic field.

  12. Defects and diffusion in semiconductors XII

    CERN Document Server

    Fisher, David J

    2010-01-01

    This twelfth volume in the series covering the latest results in the field includes abstracts of papers which have appeared since the publication of Annual Retrospective XI (Volume 282). As well as the 565 semiconductor-related abstracts, the issue includes - in line with the policy of including original papers on all of the major material groups: ""Study of Conduction Mechanism in Amorphous Se85-xTe15Bix Thin Films"" (A.Sharma and P.B.Barman), ""Structure and Optical Properties of Magnetron-Sputtered SiOx Layers with Silicon Nanoparticles"" (L.Khomenkova, N.Korsunska, T.Stara, Y.Goldstein, J.

  13. Interactions between semiconductor nanowires and living cells.

    Science.gov (United States)

    Prinz, Christelle N

    2015-06-17

    Semiconductor nanowires are increasingly used for biological applications and their small dimensions make them a promising tool for sensing and manipulating cells with minimal perturbation. In order to interface cells with nanowires in a controlled fashion, it is essential to understand the interactions between nanowires and living cells. The present paper reviews current progress in the understanding of these interactions, with knowledge gathered from studies where living cells were interfaced with vertical nanowire arrays. The effect of nanowires on cells is reported in terms of viability, cell-nanowire interface morphology, cell behavior, changes in gene expression as well as cellular stress markers. Unexplored issues and unanswered questions are discussed.

  14. Microwave Generation in Synchronized Semiconductor Superlattices

    Science.gov (United States)

    Gaifullin, M. B.; Alexeeva, N. V.; Hramov, A. E.; Makarov, V. V.; Maksimenko, V. A.; Koronovskii, A. A.; Greenaway, M. T.; Fromhold, T. M.; Patanè, A.; Mellor, C. J.; Kusmartsev, F. V.; Balanov, A. G.

    2017-04-01

    We study high-frequency generation in a system of electromagnetically coupled semiconductor superlattices fabricated on the same doped substrate. Applying a bias voltage to a single superlattice generates high-frequency current oscillations. We demonstrate that within a certain range of the applied voltage, the current oscillations within the superlattices can be self-synchronized, which leads to a dramatic rise in the generated microwave power. These results, which are in good agreement with our numerical model, open a promising practical route towards the design of high-power miniature microwave generators.

  15. Coherent manipulation of single spins in semiconductors.

    Science.gov (United States)

    Hanson, Ronald; Awschalom, David D

    2008-06-19

    During the past few years, researchers have gained unprecedented control over spins in the solid state. What was considered almost impossible a decade ago, in both conceptual and practical terms, is now a reality: single spins can be isolated, initialized, coherently manipulated and read out using both electrical and optical techniques. Progress has been made towards full control of the quantum states of single and coupled spins in a variety of semiconductors and nanostructures, and towards understanding the mechanisms through which spins lose coherence in these systems. These abilities will allow pioneering investigations of fundamental quantum-mechanical processes and provide pathways towards applications in quantum information processing.

  16. Laser thermoreflectance for semiconductor thin films metrology

    Science.gov (United States)

    Gailly, P.; Hastanin, J.; Duterte, C.; Hernandez, Y.; Lecourt, J.-B.; Kupisiewicz, A.; Martin, P.-E.; Fleury-Frenette, K.

    2012-06-01

    We present a thermoreflectance-based metrology concept applied to compound semiconductor thin films off-line characterization in the solar cells scribing process. The presented thermoreflectance setup has been used to evaluate the thermal diffusivity of thin CdTe films and to measure eventual changes in the thermal properties of 5 μm CdTe films ablated by nano and picosecond laser pulses. The temperature response of the CdTe thin film to the nanosecond heating pulse has been numerically investigated using the finite-difference time-domain (FDTD) method. The computational and experimental results have been compared.

  17. Defects and diffusion in semiconductors XIV

    CERN Document Server

    Fisher, David J

    2012-01-01

    This 14th volume in the series covers the latest results in the field of Defects and Diffusion in Semiconductor. The issue also includes some original papers: An Experimental Study of the Thermal Properties of Modified 9Cr-1Mo Steel; Physico-Mechanical Properties of Sintered Iron-Silica Sand Nanoparticle Composites: A Preliminary Study; Defect and Dislocation Density Parameters of 5251 Al Alloy Using Positron Annihilation Lifetime Technique; A Novel Computational Strategy to Enhance the Ability of Elaborate Search by Entire Swarm to Find the Best Solution in Optimization of AMCs; Synthesis and

  18. The electronic structure of impurities in semiconductors

    CERN Multimedia

    Nylandsted larsen, A; Svane, A

    2002-01-01

    The electronic structure of isolated substitutional or interstitial impurities in group IV, IV-IV, and III-V compound semiconductors will be studied. Mössbauer spectroscopy will be used to investigate the incorporation of the implanted isotopes on the proper lattice sites. The data can be directly compared to theoretical calculations using the LMTO scheme. Deep level transient spectroscopy will be used to identify the band gap levels introduced by metallic impurities, mainly in Si~and~Si$ _{x}$Ge$_{1-x}$. \\\\ \\\\

  19. Superconducting detectors for semiconductor quantum photonics

    Energy Technology Data Exchange (ETDEWEB)

    Reithmaier, Guenther M.

    2015-05-07

    In this thesis we present the first successful on-chip detection of quantum light, thereby demonstrating the monolithic integration of superconducting single photon detectors with individually addressable semiconductor quantum dots in a prototypical quantum photonic circuit. Therefore, we optimized both the deposition of high quality superconducting NbN thin films on GaAs substrates and the fabrication of superconducting detectors and successfully integrated these novel devices with GaAs/AlGaAs ridge waveguides loaded with self-assembled InGaAs quantum dots.

  20. A Theoretical Search for Supervelocity Semiconductors

    Science.gov (United States)

    1992-10-01

    Monte Carlo simulations in order to study pseudomorphic devices, real space transfer structures, and submicron MOSFETs , and 4) search for new quantum...voltage, and low parasitic resistance . Currently, most semiconductor devices employ doping techniques that control doping profiles in the vertical...100 v L’_’I,4, 0 0 1 2 3 4 5 6 Time (psec) Figure 8: Current response for drain voltage switch-off for an Alo.3Gao.7 As/GaAs RSTLT. The col- lector

  1. Dual computational basis qubit in semiconductor heterostructures

    Science.gov (United States)

    Gilbert, M. J.; Akis, R.; Ferry, D. K.

    2003-08-01

    Advances in quantum computing have revealed computing capabilities that threaten to render many of the public encryption codes useless against the hacking potential for a quantum-mechanical-based computing system. This potential forces the study of viable methods to keep vital information secure from third-party eavesdropping. In this letter, we propose a coupled electronic waveguide device to create a qubit with two computational bases. The characteristics we have obtained by simulating such devices suggest a possible way of implementing quantum cryptography in semiconductor device architectures.

  2. EDITORIAL: Semiconductor lasers: the first fifty years Semiconductor lasers: the first fifty years

    Science.gov (United States)

    Calvez, S.; Adams, M. J.

    2012-09-01

    Anniversaries call for celebrations. Since it is now fifty years since the first semiconductor lasers were reported, it is highly appropriate to celebrate this anniversary with a Special Issue dedicated to the topic. The semiconductor laser now has a major effect on our daily lives since it has been a key enabler in the development of optical fibre communications (and hence the internet and e-mail), optical storage (CDs, DVDs, etc) and barcode scanners. In the early 1960s it was impossible for most people (with the exception of very few visionaries) to foresee any of these future developments, and the first applications identified were for military purposes (range-finders, target markers, etc). Of course, many of the subsequent laser applications were made possible by developments in semiconductor materials, in the associated growth and fabrication technology, and in the increased understanding of the underlying fundamental physics. These developments continue today, so that the subject of semiconductor lasers, although mature, is in good health and continues to grow. Hence, we can be confident that the pervasive influence of semiconductor lasers will continue to develop as optoelectronics technology makes further advances into other sectors such as healthcare, security and a whole host of applications based on the global imperatives to reduce energy consumption, minimise environmental impact and conserve resources. The papers in this Special Issue are intended to tell some of the story of the last fifty years of laser development as well as to provide evidence of the current state of semiconductor laser research. Hence, there are a number of papers where the early developments are recalled by authors who played prominent parts in the story, followed by a selection of papers from authors who are active in today's exciting research. The twenty-fifth anniversary of the semiconductor laser was celebrated by the publication of a number of papers dealing with the early

  3. EDITORIAL: The 24th Nordic Semiconductor Meeting The 24th Nordic Semiconductor Meeting

    Science.gov (United States)

    Páll Gunnlaugsson, Haraldur; Nylandsted Larsen, Arne; Uhrenfeldt, Christian

    2012-03-01

    A Nordic Semiconductor Meeting is held every other year with the venue rotating amongst the Nordic countries of Denmark, Finland, Iceland, Norway and Sweden. The focus of these meetings remains 'original research and science being carried out on semiconductor materials, devices and systems'. Reports on industrial activity have usually featured. The topics have ranged from fundamental research on point defects in a semiconductor to system architecture of semiconductor electronic devices. Proceedings from these events are regularly published as a Topical Issue of Physica Scripta. All of the papers in this Topical Issue have undergone critical peer review and we wish to thank the reviewers and the authors for their cooperation, which has been instrumental in meeting the high scientific standards and quality of the series. This 24th meeting of the Nordic Semiconductor community, NSM 2011, was held at Fuglsøcentret, close to Aarhus, Denmark, 19-22 June 2011. Support was provided by the Carlsberg Foundation, Danfysik and the semiconductor group at Aarhus University. Over 30 participants presented a broad range of topics covering semiconductor materials and devices as well as related material science interests. The conference provided a forum for Nordic and international scientists to present and discuss new results and ideas concerning the fundamentals and applications of semiconductor materials. The aim of the meeting was to advance the progress of Nordic science and thus aid in future worldwide technological advances concerning technology, education, energy and the environment. The 25th Nordic Semiconductor Meeting will be organized in June 2013 in Finland, chaired by Dr Filip Tuomisto, Aalto University. A Nordic Summer School on Semiconductor Science will be organized in connection with the conference (just before), chaired by Dr Jonatan Slotte, Aalto University. Information on these events can be found at physics.aalto.fi/nsm2013. List of participants Søren Vejling

  4. Optical Regeneration and Noise in Semiconductor Devices

    DEFF Research Database (Denmark)

    Öhman, Filip

    2005-01-01

    In this report all-optical 2R-regeneration in optical communication systems is investigated. A simple regenerator device based on concatenated semiconductor optical amplifiers (SOAs) and electro absorbers (EAs) is introduced and examined. Experiments show that the monolithic SOA-EA 2R-regenerator......In this report all-optical 2R-regeneration in optical communication systems is investigated. A simple regenerator device based on concatenated semiconductor optical amplifiers (SOAs) and electro absorbers (EAs) is introduced and examined. Experiments show that the monolithic SOA-EA 2R...... sensitivity with more than 8 dB compared to the back-to-back case, using a degraded signal. The noise properties and cascadability of the proposed device are examined through modeling. Furthermore the influence of the saturation properties of the EA on the regeneration performance is investigated....... Calculations show that it is possible to increase the nonlinearity of the transfer function and improve the regenerating properties by lowering the saturation power of the EA and concatenating several SOA-EA pairs, although this also adds more noise to the signal. In order to analyze the influence...

  5. Programmable and coherent crystallization of semiconductors

    KAUST Repository

    Yu, Liyang

    2017-03-04

    The functional properties and technological utility of polycrystalline materials are largely determined by the structure, geometry, and spatial distribution of their multitude of crystals. However, crystallization is seeded through stochastic and incoherent nucleation events, limiting the ability to control or pattern the microstructure, texture, and functional properties of polycrystalline materials. We present a universal approach that can program the microstructure of materials through the coherent seeding of otherwise stochastic homogeneous nucleation events. The method relies on creating topographic variations to seed nucleation and growth at designated locations while delaying nucleation elsewhere. Each seed can thus produce a coherent growth front of crystallization with a geometry designated by the shape and arrangement of seeds. Periodic and aperiodic crystalline arrays of functional materials, such as semiconductors, can thus be created on demand and with unprecedented sophistication and ease by patterning the location and shape of the seeds. This approach is used to demonstrate printed arrays of organic thin-film transistors with remarkable performance and reproducibility owing to their demonstrated spatial control over the microstructure of organic and inorganic polycrystalline semiconductors.

  6. Semiconductor nanostructures for plasma energetic systems

    Science.gov (United States)

    Mustafaev, Alexander; Smerdov, Rostislav; Klimenkov, Boris

    2017-10-01

    In this talk we discuss the research results of the three types of ultrasmall electrodes namely the nanoelectrode arrays based on composite nanostructured porous silicon (PS) layers, porous GaP and nanocrystals of ZnO. These semiconductor materials are of great interest to nano- and optoelectronic applications by virtue of their high specific surface area and extensive capability for surface functionalization. The use of semiconductor (GaN) cathodes in photon-enhanced thermionic emission systems has also proved to be effective although only a few (less than 1%) of the incident photons exceed the 3.3 eV GaN band gap. This significant drawback provided us with a solid foundation for our research in the field of nanostructured PS, and composite materials based on it exhibiting nearly optimal parameters in terms of the band gap (1.1 eV). The band gap modification for PS nanostructured layers is possible in the range of less than 1 eV and 3 eV due to the existence of quantum confinement effect and the remarkable possibilities of PS surface alteration thus providing us with a suitable material for both cathode and anode fabrication. The obtained results are applicable for solar concentration and thermionic energy conversion systems. Dr. Sci., Ph.D, Principal Scientist, Professor.

  7. PREFACE: 16th Nordic Semiconductor Meeting

    Science.gov (United States)

    Pétur Gíslason, Hafliði; Guðmundsson, Viðar

    1994-01-01

    Some 30 years ago an informal meeting of the few Nordic specialists in semiconductor physics marked the beginning of what has become a biannual meeting of some hundred physicists and physics students from all the Nordic countries. The 16th Nordic Semiconductor Meeting took place at Laugarvatn, Iceland, June 12-15,1994. As a regional meeting the Nordic Semiconductor meeting has three characteristic features all of which distinguish it from more traditional international meetings in the field. First, it has the purpose of promoting Nordic cooperation in the international field of semiconductor physics. Research in the fields of advanced science and technology in the Nordic countries is likely to benefit from joining national forces before participating in the increasing European integration. Second, there is an unusually large fraction of graduate students amongst the participants of the Nordic Semiconductor Meeting. In fact, attending this conference is traditionally a part of the graduate program in seniconductor physics and technology. The Nordic Semiconductor Meeting is often the first conference of international character that graduate students attend in order to present a paper of poster. Third, there is an interdisciplinary quality of the meeting which is normally not the case for meetings of this size. In particular, the number of professional scientists from industry is comparable to the number of their academic colleagues. This is important for both groups, but perhaps the graduate students benefit most from presenting their results to both groups. The 16th Nordic Semiconductor Meeting, the first one in this series held in Iceland, attracted 129 active participants. The scientific programme was divided in twelve oral sessions. A novelty of this meeting was the emphasis on more fundamental physics in one of the two parallel sessions but more applied topics in the other, although the distinction was sometimes a matter of predilection. A poster session

  8. Dilute ferromagnetic semiconductors: Physics and spintronic structures

    Science.gov (United States)

    Dietl, Tomasz; Ohno, Hideo

    2014-01-01

    This review compiles results of experimental and theoretical studies on thin films and quantum structures of semiconductors with randomly distributed Mn ions, which exhibit spintronic functionalities associated with collective ferromagnetic spin ordering. Properties of p-type Mn-containing III-V as well as II-VI, IV-VI, V2-VI3, I-II-V, and elemental group IV semiconductors are described, paying particular attention to the most thoroughly investigated system (Ga,Mn)As that supports the hole-mediated ferromagnetic order up to 190 K for the net concentration of Mn spins below 10%. Multilayer structures showing efficient spin injection and spin-related magnetotransport properties as well as enabling magnetization manipulation by strain, light, electric fields, and spin currents are presented together with their impact on metal spintronics. The challenging interplay between magnetic and electronic properties in topologically trivial and nontrivial systems is described, emphasizing the entangled roles of disorder and correlation at the carrier localization boundary. Finally, the case of dilute magnetic insulators is considered, such as (Ga,Mn)N, where low-temperature spin ordering is driven by short-ranged superexchange that is ferromagnetic for certain charge states of magnetic impurities.

  9. Magnetic-field-controlled reconfigurable semiconductor logic.

    Science.gov (United States)

    Joo, Sungjung; Kim, Taeyueb; Shin, Sang Hoon; Lim, Ju Young; Hong, Jinki; Song, Jin Dong; Chang, Joonyeon; Lee, Hyun-Woo; Rhie, Kungwon; Han, Suk Hee; Shin, Kyung-Ho; Johnson, Mark

    2013-02-07

    Logic devices based on magnetism show promise for increasing computational efficiency while decreasing consumed power. They offer zero quiescent power and yet combine novel functions such as programmable logic operation and non-volatile built-in memory. However, practical efforts to adapt a magnetic device to logic suffer from a low signal-to-noise ratio and other performance attributes that are not adequate for logic gates. Rather than exploiting magnetoresistive effects that result from spin-dependent transport of carriers, we have approached the development of a magnetic logic device in a different way: we use the phenomenon of large magnetoresistance found in non-magnetic semiconductors in high electric fields. Here we report a device showing a strong diode characteristic that is highly sensitive to both the sign and the magnitude of an external magnetic field, offering a reversible change between two different characteristic states by the application of a magnetic field. This feature results from magnetic control of carrier generation and recombination in an InSb p-n bilayer channel. Simple circuits combining such elementary devices are fabricated and tested, and Boolean logic functions including AND, OR, NAND and NOR are performed. They are programmed dynamically by external electric or magnetic signals, demonstrating magnetic-field-controlled semiconductor reconfigurable logic at room temperature. This magnetic technology permits a new kind of spintronic device, characterized as a current switch rather than a voltage switch, and provides a simple and compact platform for non-volatile reconfigurable logic devices.

  10. Bipolar magnetic semiconductor in silicene nanoribbons

    Science.gov (United States)

    Farghadan, Rouhollah

    2017-08-01

    A theoretical study was presented on generation of spin polarization in silicene nanoribbons using the single-band tight-binding approximation and the non-equilibrium Green's function formalism. We focused on the effect of electric and exchange magnetic fields on the spin-filter capabilities of zigzag-edge silicene nanoribbons in the presence of the intrinsic spin-orbit interaction. The results show that a robust bipolar magnetic semiconductor with controllable spin-flip and spin-conserved gaps can be obtained when exchange magnetic and electric field strengths are both larger than the intrinsic spin-orbit interaction. Therefore, zigzag silicene nanoribbons could act as bipolar and perfect spin filter devices with a large spin-polarized current and a reversible spin polarization in the vicinity of the Fermi energy. We also investigated the effect of edge roughness and found that the bipolar magnetic semiconductor features are robust against edge disorder in silicene nanoribbon junctions. These results may be useful in multifunctional spin devices based on silicene nanoribbons.

  11. Semiconductor Quantum Dots with Photoresponsive Ligands.

    Science.gov (United States)

    Sansalone, Lorenzo; Tang, Sicheng; Zhang, Yang; Thapaliya, Ek Raj; Raymo, Françisco M; Garcia-Amorós, Jaume

    2016-10-01

    Photochromic or photocaged ligands can be anchored to the outer shell of semiconductor quantum dots in order to control the photophysical properties of these inorganic nanocrystals with optical stimulations. One of the two interconvertible states of the photoresponsive ligands can be designed to accept either an electron or energy from the excited quantum dots and quench their luminescence. Under these conditions, the reversible transformations of photochromic ligands or the irreversible cleavage of photocaged counterparts translates into the possibility to switch luminescence with external control. As an alternative to regulating the photophysics of a quantum dot via the photochemistry of its ligands, the photochemistry of the latter can be controlled by relying on the photophysics of the former. The transfer of excitation energy from a quantum dot to a photocaged ligand populates the excited state of the species adsorbed on the nanocrystal to induce a photochemical reaction. This mechanism, in conjunction with the large two-photon absorption cross section of quantum dots, can be exploited to release nitric oxide or to generate singlet oxygen under near-infrared irradiation. Thus, the combination of semiconductor quantum dots and photoresponsive ligands offers the opportunity to assemble nanostructured constructs with specific functions on the basis of electron or energy transfer processes. The photoswitchable luminescence and ability to photoinduce the release of reactive chemicals, associated with the resulting systems, can be particularly valuable in biomedical research and can, ultimately, lead to the realization of imaging probes for diagnostic applications as well as to therapeutic agents for the treatment of cancer.

  12. Amorphous Semiconductors: From Photocatalyst to Computer Memory

    Science.gov (United States)

    Sundararajan, Mayur

    Amorphous semiconductors are useful in many applications like solar cells, thin film displays, sensors, electrophotography, etc. The dissertation contains four projects. In the first three projects, semiconductor glasses which are a subset of amorphous semiconductors were studied. The last project is about exploring the strengths and constraints of two analysis programs which calculate the particle size information from experimental Small Angle X-ray Scattering data. By definition, glasses have a random atomic arrangement with no order beyond the nearest neighbor, but strangely there exists an Intermediate Range Order (IRO). The origin of IRO is still not clearly understood, but various models have been proposed. The signature of IRO is the First Sharp Diffraction Peak(FSDP) observed in x-ray and neutron scattering data. The FSDP of TiO 2 SiO2 glass photocatalyst with different Ti:Si ratio from SAXS data was measured to test the theoretical models. The experimental results along with its computer simulation results strongly supported one of two leading models. It was also found that the effect of doping IRO on TiO2 SiO2 is severe in mesoporous form than the bulk form. Glass semiconductors in mesoporous form are very useful photocatalysts due to their large specific surface area. Solar energy conversion of photocatalysts greatly depends on their bandgap, but very few photocatalysts have the optical bandgap covering the whole visible region of solar spectrum leading to poor efficiency. A physical method was developed to manipulate the bandgap of mesoporous photocatalysts, by using the anisotropic thermal expansion and stressed glass network properties of mesoporous glasses. The anisotropic thermal expansion was established by S/WAXS characterization of mesoporous silica (MCM-41). The residual stress in the glass network of mesoporous glasses was already known for an earlier work. The new method was initially applied on mesoporous TiPO4, and the results were

  13. Slow Light at High Frequencies in an Amplifying Semiconductor Waveguide

    DEFF Research Database (Denmark)

    Öhman, Filip; Yvind, Kresten; Mørk, Jesper

    2006-01-01

    We demonstrate slow-down of a modulated light signal in a semiconductor waveguide. Concatenated amplifying and absorbing sections simultaneously achieve both amplification and a controllable time delay at 15 GHz.......We demonstrate slow-down of a modulated light signal in a semiconductor waveguide. Concatenated amplifying and absorbing sections simultaneously achieve both amplification and a controllable time delay at 15 GHz....

  14. Einstein relation in compound semiconductors and their nanostructures

    CERN Document Server

    Bhattacharya, Sitangshu

    2008-01-01

    Deals with the Einstein relation in compound semiconductors and their nanostructures. This book considers materials such as nonlinear optical, III-V, ternary, quaternary, II-VI, IV-VI, Bismuth, stressed compounds, quantum wells, quantum wires, nipi structures, carbon nanotubes, heavily doped semiconductors, and inversion layers.

  15. Imaging the motion of excitonic complexes in semiconductor quantum wells

    NARCIS (Netherlands)

    Pulizzi, Fabio

    2003-01-01

    The low temperature optical properties of semiconductor quantum wells are dominated by excitonic complexes, i.e. a few charges bound together by the mutual Coulomb interaction. Excitonic complexes have been widely studied in the past not only for their importance in the physics of semiconductors,

  16. Electron transport and coherence in semiconductor quantum dots and rings

    NARCIS (Netherlands)

    Van der Wiel, W.G.

    2002-01-01

    A number of experiments on electron transport and coherence in semiconductor vertical and lateral quantum dots and semiconductor rings is described. Quantum dots are often referred to as "artificial atoms", because of their similarities with real atoms. Examples of such atom-like properties that

  17. The features of modelling semiconductor lasers with a wide contact

    Directory of Open Access Journals (Sweden)

    Rzhanov Alexey

    2017-01-01

    Full Text Available The aspects of calculating the dynamics and statics of powerful semiconductor laser diodes radiation are investigated. It takes into account the main physical mechanisms influencing power, spectral composition, far and near field of laser radiation. It outlines a dynamic distributed model of a semiconductor laser with a wide contact and possible algorithms for its implementation.

  18. Radiation hardness of semiconductor detectors for high-energy physics

    Energy Technology Data Exchange (ETDEWEB)

    Khludkov, S.S.; Stepanov, V.E.; Tolbanov, O.P. [Tomskij Gosudarstvennyj Univ., Tomsk (Russian Federation). Sibirskij Fiziko-Tekhnicheskij Inst.

    1996-06-14

    The concept of radiation hardness of semiconductor materials in terms of local charge neutrality is proposed. Deep centres are invoked to play the basic role in the attainment of radiation hardness by high-resistivity semiconductor charged particle detectors exposed to neutron irradiation. (author).

  19. Fast processes in semiconductor optical amplifiers: theory and experiment

    DEFF Research Database (Denmark)

    Mørk, Jesper

    2002-01-01

    We review the physical processes responsible for ultrafast gain and index dynamics in semiconductor optical amplifiers and discuss their impact on optical switching applications......We review the physical processes responsible for ultrafast gain and index dynamics in semiconductor optical amplifiers and discuss their impact on optical switching applications...

  20. Parity lifetime of bound states in a proximitized semiconductor nanowire

    DEFF Research Database (Denmark)

    Higginbotham, Andrew Patrick; Albrecht, Sven Marian; Kirsanskas, Gediminas

    2015-01-01

    superconductor layer, yielding an isolated, proximitized nanowire segment. We identify Andreev-like bound states in the semiconductor via bias spectroscopy, determine the characteristic temperatures and magnetic fields for quasiparticle excitations, and extract a parity lifetime (poisoning time) of the bound...... state in the semiconductor exceeding 10 ms....

  1. Tight-Binding Description of Impurity States in Semiconductors

    Science.gov (United States)

    Dominguez-Adame, F.

    2012-01-01

    Introductory textbooks in solid state physics usually present the hydrogenic impurity model to calculate the energy of carriers bound to donors or acceptors in semiconductors. This model treats the pure semiconductor as a homogeneous medium and the impurity is represented as a fixed point charge. This approach is only valid for shallow impurities…

  2. Ultrafast optical signal processing using semiconductor optical devices

    DEFF Research Database (Denmark)

    Mørk, Jesper; Bischoff, Svend; Berg, Tommy Winther

    2002-01-01

    We discuss the operation principles of semiconductor devices for ultrafast optical processing, emphasizing the physical processes affecting the device characteristics and the approaches taken to simulate these.......We discuss the operation principles of semiconductor devices for ultrafast optical processing, emphasizing the physical processes affecting the device characteristics and the approaches taken to simulate these....

  3. The pursuit of electrically-driven organic semiconductor lasers

    NARCIS (Netherlands)

    Bisri, Satria Zulkarnaen; Takenobu, Taishi; Iwasa, Yoshihiro

    2014-01-01

    Organic semiconductors have many favourable and plastic-like optical properties that are promising for the development of low energy consuming laser devices. Although optically-pumped organic semiconductor lasers have been demonstrated since the early days of lasers, electrically-driven organic

  4. The physics of semiconductors an introduction including nanophysics and applications

    CERN Document Server

    Grundmann, Marius

    2016-01-01

    The 3rd edition of this successful textbook contains ample material for a comprehensive upper-level undergraduate or beginning graduate course, guiding readers to the point where they can choose a special topic and begin supervised research. The textbook provides a balance between essential aspects of solid-state and semiconductor physics, on the one hand, and the principles of various semiconductor devices and their applications in electronic and photonic devices, on the other. It highlights many practical aspects of semiconductors such as alloys, strain, heterostructures, nanostructures, that are necessary in modern semiconductor research but typically omitted in textbooks. Coverage also includes additional advanced topics, such as Bragg mirrors, resonators, polarized and magnetic semiconductors, nanowires, quantum dots, multi-junction solar cells, thin film transistors, carbon-based nanostructures and transparent conductive oxides. The text derives explicit formulas for many results to support better under...

  5. Tailoring Mixed-Halide, Wide-Gap Perovskites via Multistep Conversion Process

    DEFF Research Database (Denmark)

    Bae, Dowon; Palmstrom, Axel; Roelofs, Katherine

    2016-01-01

    Wide-band-gap mixed-halide CH3NH3PbI3–XBrX-based solar cells have been prepared by means of a sequential spin-coating process. The spin-rate for PbI2 as well as its repetitive deposition are important in determining the cross-sectional shape and surface morphology of perovskite, and, consequently......, J–V performance. A perovskite solar cell converted from PbI2 with a dense bottom layer and porous top layer achieved higher device performance than those of analogue cells with a dense PbI2 top layer. This work demonstrates a facile way to control PbI2 film configuration and morphology simply...

  6. Tailoring Mixed-Halide, Wide-Gap Perovskites via Multistep Conversion Process

    NARCIS (Netherlands)

    Bae, D.; Palmstrom, A.; Roelofs, K.; Mei, Bastian Timo; Chorkendorf, I.; Bent, S.F.; Vesborg, P.C.

    2016-01-01

    Wide-band-gap mixed-halide CH3NH3PbI3–XBrX-based solar cells have been prepared by means of a sequential spin-coating process. The spin-rate for PbI2 as well as its repetitive deposition are important in determining the cross-sectional shape and surface morphology of perovskite, and, consequently,

  7. A wide-gap a-SiC:H PV-powered electrochromic window coating

    Energy Technology Data Exchange (ETDEWEB)

    Gao, W.; Lee, S.H.; Xu, Y.; Benson, D.K.; Deb, S.K.; Branz, H.M. [National Renewable Energy Lab., Golden, CO (United States)

    1998-09-01

    The authors report on the first monolithic, amorphous-silicon-based, photovoltaic-powered electrochromic window coating. The coating employs a wide bandgap a-Si{sub 1{minus}x}C{sub x}:H n-i-p photovoltaic (PV) cell as a semitransparent power supply, and a Li{sub y}WO{sub 3}/LiAlF{sub 4}/V{sub 2}O{sub 5} electrochromic (EC) device as an optical-transmittance modulator. The EC device is deposited directly on top of a PV cell that coats a glass substrate. The a-Si{sub 1{minus}x}C{sub x}:H PV cell has a Tauc gap of 2.2 eV and a transmittance of 60--80% over a large portion of the visible light spectrum. The authors reduced the thickness of the device to about 600 {angstrom} while maintaining a 1-sun open-circuit voltage of 0.9 V and short-circuit current of 2 mA/cm{sup 2}. The prototype 16 cm{sup 2} PV/EC device modulates the transmittance by more than 60% over a large portion of the visible spectrum. The coloring and bleaching times of the EC device are approximately 1 minute under normal operating conditions ({+-} 1 volt). A brief description of photoelectrochromic windows study is also given.

  8. Development of thin film encapsulation process for piezoresistive MEMS gyroscope with wide gaps

    Science.gov (United States)

    Ayanoor-Vitikkate, Vipin

    The gyroscope is an inertial sensor used to measure the angular rate of a rotating object. This helps to determine the pitch and yaw rate of any moving body. A number of applications have been developed for consumer and automotive markets, for e.g. vehicle stability control, navigation assist, roll over detection. These are primarily used in high-end cars, where cost is not a major factor. Other areas where a MEMS Gyro can be used are robotics, camcorder stabilization, virtual reality, and more. Primarily due to cost and the size most of these applications have not reached any significant volume. One reason for this is the relatively high cost of MEMS gyros compared to other MEMS sensors like accelerometers or pressure sensors. Generally the cost of packaging a MEMS sensor is about 85-90% of the total cost. Currently most MEMS based gyroscopes are made using bulk or surface micromachining, after which they are packaged using wafer bonding. This unfortunately leads to wastage of silicon and increase in the package size, thus reducing the yield. One way to reduce the cost of packaging is by wafer scale thin film encapsulation of MEMS gyroscopes. The goal of the present work is to fabricate a rate grade MEMS gyroscope and encapsulate it by modifying an existing thin-film encapsulation technique. Packaging is an important step towards commercialization of the device and we plan to use thin wafer scale encapsulation technique developed previously in our group to package these devices. The silicon micro machined gyroscope will be fabricated on SOI (Silicon-on-Insulator) wafers using Bosch DRIE etching techniques. The encapsulation of the device is carried out using epitaxial polysilicon in order to provide a high vacuum inside the device chamber. The advantages offered by this technique are the reduction in area of the die and thus less silicon surface is wasted. In addition to this the encapsulation technique helps in creating a vacuum inside the micro device, which reduces the damping effects and hence increases the quality factor Q of the gyro thus increasing the sensitivity. For this purpose a silicon-based gyroscope has been designed, which will help in the characterization of the device. We hope to reduce the size and cost of MEMS gyros using technique while increasing the performance characteristics.

  9. Study on Wide-gap Gallium-nitride Based Films and Their Quantum-dots Devices

    Science.gov (United States)

    2006-09-05

    The tilt angle SEM was used to display whole device after cutting. The white circle c and circle d region were the device edge. The corss-section of...the sidewall at circle c and circle d was shown in Figure 3.1.1.2(c) and Figure 3.1.1.2(d). Figure 3.1.1.2(c) shown the cross-section of the nano-rod... circle c region in (a) (d) the cross-section profile of circle d region in (a) (From Hwang’s group and cooperate with S. C. Hsu) 58 Figure 3.1.1.3

  10. Methods of producing free-standing semiconductors using sacrificial buffer layers and recyclable substrates

    Science.gov (United States)

    Ptak, Aaron Joseph; Lin, Yong; Norman, Andrew; Alberi, Kirstin

    2015-05-26

    A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a spinel substrate using a sacrificial buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The sacrificial buffer material and semiconductor materials may be deposited using lattice-matching epitaxy or coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The sacrificial buffer layer may be dissolved using an epitaxial liftoff technique in order to separate the semiconductor device from the spinel substrate, and the spinel substrate may be reused in the subsequent fabrication of other semiconductor devices. The low-defect density semiconductor materials produced using this method result in the enhanced performance of the semiconductor devices that incorporate the semiconductor materials.

  11. Gain and Index Dynamics in Semiconductor Lasers

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher

    . The increasing demand for communication bandwidth has made the study of ultrafast processes in SOAs an important one. The ultimate limits to the speed of nonlinear optical signal processing can only be reached by proper materials design and engineering. We have seen that the active region in SOAs has gradually...... changed character from bulk semiconductor to quantum wells and most recently to quantum dots. By quantum confinement of the carriers, the light-matter interactions can be significantly modified and the optical properties, including dynamics, can be engineered to match the required functionalities...... and specifications. We have measured ultrafast gain and index dynamics of SOAs in pump-and-probe experiments applying 100 fs pulses and a heterodyne detection scheme, where both amplitude and phase of the probe pulses are determined. The gain depletion, and associated index change, and the subsequent recovery afte...

  12. Two-dimensional Semiconductor-Superconductor Hybrids

    DEFF Research Database (Denmark)

    Suominen, Henri Juhani

    heterostructures, observing clear evidence of supercurrent, and the first direct spectroscopy of an induced superconducting gap in a two-dimensional electron gas. Nonetheless, these experiments reveal inhomogeneous contacts and a soft-induced superconducting gap, likely due to disorder at the Sm-S interface....... To overcome these issues we integrate the superconductor directly into the semiconducting material growth stack, depositing it in-situ in a molecular beam epitaxy system under high vacuum. We present a number of experiments on these hybrid heterostructures, demonstrating near unity interface transparency...... with previous reports of Majorana modes in semiconductor nanowires. By offering a patternable two-dimensional platform, our approach opens up the door to experiments probing the predicted topological properties in this system....

  13. Compound semiconductor materials, devices and circuits

    Science.gov (United States)

    Shealy, J. R.; Eastman, L. F.; Wolf, E. D.; Tasker, P. J.; Krusius, J. P.

    1988-06-01

    This one year research program on compound semiconductor materials growth, devices and circuits has focused on: (1) organometallic vapor phase epitaxy (OMVPE) of GaInP/GaAs and AlInP/GaInP superlattices; (2) enhancement of heterostructure device speed performance via strain layer superlattices and mushroom gates in modulation doped FET's (MODFET's), and inserted tunnel barriers heterojunction bipolar devices (HBT); (3) fabrication and characterization of MODFET devices with gate lengths to 50 nm; (4) self-consistent Monte Carlo transport formulation and its application to small graded heterostructure devices; (5) optical modulation based on the quantum confined Stark effect; and (6) femtosecond spectroscopy of hot carrier processes using the visible Rh6G laser and a new UV BaB2O4 laser.

  14. Solar Water Splitting Using Semiconductor Photocatalyst Powders

    KAUST Repository

    Takanabe, Kazuhiro

    2015-07-01

    Solar energy conversion is essential to address the gap between energy production and increasing demand. Large scale energy generation from solar energy can only be achieved through equally large scale collection of the solar spectrum. Overall water splitting using heterogeneous photocatalysts with a single semiconductor enables the direct generation of H from photoreactors and is one of the most economical technologies for large-scale production of solar fuels. Efficient photocatalyst materials are essential to make this process feasible for future technologies. To achieve efficient photocatalysis for overall water splitting, all of the parameters involved at different time scales should be improved because the overall efficiency is obtained by the multiplication of all these fundamental efficiencies. Accumulation of knowledge ranging from solid-state physics to electrochemistry and a multidisciplinary approach to conduct various measurements are inevitable to be able to understand photocatalysis fully and to improve its efficiency.

  15. Blue emitting organic semiconductors under high pressure

    DEFF Research Database (Denmark)

    Knaapila, Matti; Guha, Suchismita

    2016-01-01

    highlighted by high pressure optical spectroscopy whilst analogous x-ray diffraction experiments remain less frequent. By focusing on a class of blue-emitting π-conjugated polymers, polyfluorenes, this article reviews optical spectroscopic studies under hydrostatic pressure, addressing the impact of molecular......This review describes essential optical and emerging structural experiments that use high GPa range hydrostatic pressure to probe physical phenomena in blue-emitting organic semiconductors including π-conjugated polyfluorene and related compounds. The work emphasizes molecular structure...... and intermolecular self-organization that typically determine transport and optical emission in π-conjugated oligomers and polymers. In this context, hydrostatic pressure through diamond anvil cells has proven to be an elegant tool to control structure and interactions without chemical intervention. This has been...

  16. Superconductivity in compensated and uncompensated semiconductors

    Directory of Open Access Journals (Sweden)

    Youichi Yanase and Naoyuki Yorozu

    2008-01-01

    Full Text Available We investigate the localization and superconductivity in heavily doped semiconductors. The crossover from the superconductivity in the host band to that in the impurity band is described on the basis of the disordered three-dimensional attractive Hubbard model for binary alloys. The microscopic inhomogeneity and the thermal superconducting fluctuation are taken into account using the self-consistent 1-loop order theory. The superconductor-insulator transition accompanies the crossover from the host band to the impurity band. We point out an enhancement of the critical temperature Tc around the crossover. Further localization of electron wave functions leads to the localization of Cooper pairs and induces the pseudogap. We find that both the doping compensation by additional donors and the carrier increase by additional acceptors suppress the superconductivity. A theoretical interpretation is proposed for the superconductivity in the boron-doped diamond, SiC, and Si.

  17. The structure and morphology of semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Kadavanich, Andreas V. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1997-11-01

    Colloidal semiconductor nanocrystals were studied using High Resolution Transmission Electron Microscopy (HRTEM). Organically capped nanocrystals were found to have faceted shapes consistent with Wulff polyhedra after the effects of capping ligands on surface energies were taken into account. The basic shape thus derived for wurtzite (WZ) structure CdSe nanocrystals capped by tri-octyl phosphine oxide (TOPO) was a truncated hexagonal prism, elongated alone the <001> axis with (100) and (002) facets. This structure has C{sub 3v} point group symmetry. The main defect in this structure is a stacking fault (a single layer of zinc blende type stacking), which does not significantly affect the shape (does not alter the point group).

  18. Potentiometric Measurements of Semiconductor Nanocrystal Redox Potentials.

    Science.gov (United States)

    Carroll, Gerard M; Brozek, Carl K; Hartstein, Kimberly H; Tsui, Emily Y; Gamelin, Daniel R

    2016-04-06

    A potentiometric method for measuring redox potentials of colloidal semiconductor nanocrystals (NCs) is described. Fermi levels of colloidal ZnO NCs are measured in situ during photodoping, allowing correlation of NC redox potentials and reduction levels. Excellent agreement is found between electrochemical and optical redox-indicator methods. Potentiometry is also reported for colloidal CdSe NCs, which show more negative conduction-band-edge potentials than in ZnO. This difference is highlighted by spontaneous electron transfer from reduced CdSe NCs to ZnO NCs in solution, with potentiometry providing a measure of the inter-NC electron-transfer driving force. Future applications of NC potentiometry are briefly discussed.

  19. Semiconductor laser with longitudinal-mode selection

    Science.gov (United States)

    Masloboev, Iu. P.; Poltoratskii, E. A.; Suris, R. A.; Shtofich, S. V.

    1980-06-01

    A new method for longitudinal-mode selection in a semiconductor laser is proposed, based on the conversion of such modes into higher-order transverse modes which can subsequently be filtered out. The key element of this design is an interference cell that is based on an active waveguide, consisting of two branches of different length. If this interference cell is placed between the mirrors of a resonator, and if the emission in higher-order modes is suppressed by some device, the new type of laser with longitudinal-mode selection results. Such a laser would emit in a single mode over a broad range of pump currents, and could be used as an exceptionally good light source for integrated optics and high-speed fiber-optics communications.

  20. Optical processes in dilute nitrides Semiconductors; Alloys

    CERN Document Server

    Potter, R J

    2003-01-01

    This thesis is concerned with the narrow bandgap semiconductor alloys known as dilute nitrides. The initial part of this project was concerned with characterisation of chemical beam epitaxy (CBE) grown samples so that growth techniques could be refined. Early samples show evidence of structural/compositional disorder resulting from the large miscibility gap induced by nitrogen. Non-equilibrium growth was employed to overcome this, eventually resulting in improved material. In the second part of this project, steady-state and time-resolved photoluminescence, along with photomodulated reflectance were employed to investigate the optical properties of molecular beam epitaxy (MBE) grown GalnNAs, GaNAs and InGaAs quantum wells (QWs). Low temperature results show evidence of carrier localization, which was interpreted in terms of structural/compositional fluctuations induced by the nitrogen incorporation. Poor photoluminescence efficiency and rapid decay of emission kinetics indicate the presence of strong non-radi...