Sample records for binary iii-v semiconductors

  1. III-V semiconductor materials and devices

    CERN Document Server

    Malik, R J


    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.

  2. III-V semiconductor solid solution single crystal growth (United States)

    Gertner, E. R.


    The feasibility and desirability of space growth of bulk IR semiconductor crystals for use as substrates for epitaxial IR detector material were researched. A III-V ternary compound (GaInSb) and a II-VI binary compound were considered. Vapor epitaxy and quaternary epitaxy techniques were found to be sufficient to permit the use of ground based binary III-V crystals for all major device applications. Float zoning of CdTe was found to be a potentially successful approach to obtaining high quality substrate material, but further experiments were required.

  3. III-V semiconductor devices integrated with silicon III-V semiconductor devices integrated with silicon (United States)

    Hopkinson, Mark; Martin, Trevor; Smowton, Peter


    The integration of III-V semiconductor devices with silicon is one of the most topical challenges in current electronic materials research. The combination has the potential to exploit the unique optical and electronic functionality of III-V technology with the signal processing capabilities and advanced low-cost volume production techniques associated with silicon. Key industrial drivers include the use of high mobility III-V channel materials (InGaAs, InAs, InSb) to extend the performance of Si CMOS, the unification of electronics and photonics by combining photonic components (GaAs, InP) with a silicon platform for next-generation optical interconnects and the exploitation of large-area silicon substrates and high-volume Si processing capabilities to meet the challenges of low-cost production, a challenge which is particularly important for GaN-based devices in both power management and lighting applications. The diverse nature of the III-V and Si device approaches, materials technologies and the distinct differences between industrial Si and III-V processing have provided a major barrier to integration in the past. However, advances over the last decade in areas such as die transfer, wafer fusion and epitaxial growth have promoted widespread renewed interest. It is now timely to bring some of these topics together in a special issue covering a range of approaches and materials providing a snapshot of recent progress across the field. The issue opens a paper describing a strategy for the epitaxial integration of photonic devices where Kataria et al describe progress in the lateral overgrowth of InP/Si. As an alternative, Benjoucef and Reithmaier report on the potential of InAs quantum dots grown direct onto Si surfaces whilst Sandall et al describe the properties of similar InAs quantum dots as an optical modulator device. As an alternative to epitaxial integration approaches, Yokoyama et al describe a wafer bonding approach using a buried oxide concept, Corbett

  4. Active III-V Semiconductor Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Ek, Sara; Chen, Yaohui; Schubert, Martin;


    We experimentally demonstrate enhanced amplified spontaneous emission in a quantum well III-V semiconductor photonic crystal waveguide slab. The effect is described by enhanced light matter interaction with the decrease of the group velocity. These are promising results for future compact devices...... for terabit/s communication, such as miniaturised semiconductor optical amplifiers and mode-locked lasers....

  5. Spectroscopic characterization of III-V semiconductor nanomaterials (United States)

    Crankshaw, Shanna Marie

    III-V semiconductor materials form a broad basis for optoelectronic applications, including the broad basis of the telecom industry as well as smaller markets for high-mobility transistors. In a somewhat analogous manner as the traditional silicon logic industry has so heavily depended upon process manufacturing development, optoelectronics often relies instead on materials innovations. This thesis focuses particularly on III-V semiconductor nanomaterials, detailed characterization of which is invaluable for translating the exhibited behavior into useful applications. Specifically, the original research described in these thesis chapters is an investigation of semiconductors at a fundamental materials level, because the nanostructures in which they appear crystallize in quite atypical forms for the given semiconductors. Rather than restricting the experimental approaches to any one particular technique, many different types of optical spectroscopies are developed and applied where relevant to elucidate the connection between the crystalline structure and exhibited properties. In the first chapters, for example, a wurtzite crystalline form of the prototypical zincblende III-V binary semiconductor, GaAs, is explored through polarization-dependent Raman spectroscopy and temperature-dependent photoluminescence, as well as second-harmonic generation (SHG). The altered symmetry properties of the wurtzite crystalline structure are particularly evident in the Raman and SHG polarization dependences, all within a bulk material realm. A rather different but deeply elegant aspect of crystalline symmetry in GaAs is explored in a separate study on zincblende GaAs samples quantum-confined in one direction, i.e. quantum well structures, whose quantization direction corresponds to the (110) direction. The (110) orientation modifies the low-temperature electron spin relaxation mechanisms available compared to the usual (001) samples, leading to altered spin coherence times explored

  6. The coupling of thermochemistry and phase diagrams for group III-V semiconductor systems. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, T.J.


    The project was directed at linking the thermochemical properties of III-V compound semiconductors systems with the reported phase diagrams. The solid-liquid phase equilibrium problem was formulated and three approaches to calculating the reduced standard state chemical potential were identified and values were calculated. In addition, thermochemical values for critical properties were measured using solid state electrochemical techniques. These values, along with the standard state chemical potentials and other available thermochemical and phase diagram data, were combined with a critical assessment of selected III-V systems. This work was culminated with a comprehensive assessment of all the III-V binary systems. A novel aspect of the experimental part of this project was the demonstration of the use of a liquid encapsulate to measure component activities by a solid state emf technique in liquid III-V systems that exhibit high vapor pressures at the measurement temperature.

  7. Nanometre-scale electronics with III-V compound semiconductors. (United States)

    del Alamo, Jesús A


    For 50 years the exponential rise in the power of electronics has been fuelled by an increase in the density of silicon complementary metal-oxide-semiconductor (CMOS) transistors and improvements to their logic performance. But silicon transistor scaling is now reaching its limits, threatening to end the microelectronics revolution. Attention is turning to a family of materials that is well placed to address this problem: group III-V compound semiconductors. The outstanding electron transport properties of these materials might be central to the development of the first nanometre-scale logic transistors.

  8. III-V aresenide-nitride semiconductor materials and devices (United States)

    Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)


    III-V arsenide-nitride semiconductor crystals, methods for producing such crystals and devices employing such crystals. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

  9. Magnetooptical investigations on ferromagnetic III-V-semiconductors; Magnetooptische Untersuchungen an ferromagnetischen III-V-Halbleitern

    Energy Technology Data Exchange (ETDEWEB)

    Winter, Andreas


    Magnetooptical Kerr effect (MOKE) and Magnetic Circular Dichroism (MCD) have been used to investigate magnetic as well as bandstructure properties of diluted magnetic III-V-semiconductors containing Mn. In these ferromagnetic systems it has been found that the strength of the observed effects depends linearly on the magnetization of the samples with no influence of the external magnetic field. The magnetooptical effects allowed the recording of hysteresis loops of GaMnAs, GaMnSb, InMnAs and InMnSb samples for different temperatures and in the case of GaMnAs also for different alignments of the external magnetic field with respect to the easy axis of magnetization. The Stoner-Wohlfahrt-Model has been used to describe the resulting shapes of the loops yielding the magnetic anisotropy parameters of the samples. For magnetically saturated samples, spectra of MOKE and MCD have been recorded. Contrary to pure III-V-semiconductors, which exhibit lots of sharp resonances due to interband transitions between Landau levels, III-Mn-V-semi-conductors how only very few (or just one) considerably broad resonance(s). Their spectral position(s) do(es) neither depend upon the magnetic field as it would be the case for pure III-V-semiconductors nor the magnetization. Only the amplitude increases linearly with the magnetization. Utilizing a kp-theory it has been possible to describe the observed dependencies. Valence- and conduction-band are split into Landau levels by the external magnetic field and, in addition to the Zeeman-effect, the spin-levels are split by the exchange interaction between the localized electrons of the Mn ions and the free carriers which is proportional to the magnetization of the samples. This splitting is much bigger than the Landau level splitting. Due to an inhomogeneous distribution of the Mn ions and due to the high carrier density the Landau levels are strongly broadened and their structure is not observable. Owing to the high carrier-concentration in

  10. Subsurface dimerization in III-V semiconductor (001) surfaces

    DEFF Research Database (Denmark)

    Kumpf, C.; Marks, L.D.; Ellis, D.


    We present the atomic structure of the c(8 X 2) reconstructions of InSb-, InAs-, and GaAs-(001) surfaces as determined by surface x-ray diffraction using direct methods. Contrary to common belief, group III dimers are not prominent on the surface, instead subsurface dimerization of group m atoms ...... takes place in the second bilayer, accompanied by a major rearrangement of the surface atoms above the dimers to form linear arrays. By varying the occupancies of four surface sites the (001)-c(8 X 2) reconstructions of III-V semiconductors can be described in a unified model....

  11. Enhancing Hole Mobility in III-V Semiconductors (United States)


    enhance the hole mobility and thereby improve the performance of a p-channel FET. Laikhtman et al.7 presented a modeling study of the InGaAs/ AlGaAs III-V semicon- ductors, polar scattering is the dominant scattering mecha- nism as non-polar optical phonons do not interact with the electrons due...right) for upper valence band in GaAs for (a) biaxial compression and (b) uniaxial compression. TABLE I. Relevant properties of different semiconductor

  12. Antisites in III-V semiconductors: Density functional theory calculations

    KAUST Repository

    Chroneos, A.


    Density functional based simulation, corrected for finite size effects, is used to investigate systematically the formation of antisite defects in III-V semiconductors (III=Al, Ga, and In and V=P, As, and Sb). Different charge states are modelled as a function of the Fermi level and under different growth conditions. The formation energies of group III antisites (III V q) decrease with increasing covalent radius of the group V atom though not group III radius, whereas group V antisites (V I I I q) show a consistent decrease in formation energies with increase in group III and group V covalent radii. In general, III V q defects dominate under III-rich conditions and V I I I q under V-rich conditions. Comparison with equivalent vacancy formation energy simulations shows that while antisite concentrations are always dominant under stoichiometric conditions, modest variation in growth or doping conditions can lead to a significantly higher concentration of vacancies. © 2014 AIP Publishing LLC.

  13. Organic / IV, III-V Semiconductor Hybrid Solar Cells

    Directory of Open Access Journals (Sweden)

    Pang-Leen Ong


    Full Text Available We present a review of the emerging class of hybrid solar cells based on organic-semiconductor (Group IV, III-V, nanocomposites, which states separately from dye synthesized, polymer-metal oxides and organic-inorganic (Group II-VI nanocomposite photovoltaics. The structure of such hybrid cell comprises of an organic active material (p-type deposited by coating, printing or spraying technique on the surface of bulk or nanostructured semiconductor (n-type forming a heterojunction between the two materials. Organic components include various photosensitive monomers (e.g., phtalocyanines or porphyrines, conjugated polymers, and carbon nanotubes. Mechanisms of the charge separation at the interface and their transport are discussed. Also, perspectives on the future development of such hybrid cells and comparative analysis with other classes of photovoltaics of third generation are presented.

  14. III - V semiconductor structures for biosensor and molecular electronics applications

    Energy Technology Data Exchange (ETDEWEB)

    Luber, S.M.


    The present work reports on the employment of III-V semiconductor structures to biosensor and molecular electronics applications. In the first part a sensor based on a surface-near two dimensional electron gas for a use in biological environment is studied. Such a two dimensional electron gas inherently forms in a molecular beam epitaxy (MBE) grown, doped aluminum gallium arsenide - gallium arsenide (AlGaAs-GaAs) heterostructure. Due to the intrinsic instability of GaAs in aqueous solutions the device is passivated by deposition of a monolayer of 4'-substituted mercaptobiphenyl molecules. The influence of these molecules which bind to the GaAs via a sulfur group is investigated by Kelvin probe measurements in air. They reveal a dependence of GaAs electron affinity on the intrinsic molecular dipole moment of the mercaptobiphenyls. Furthermore, transient surface photovoltage measurements are presented which demonstrate an additional influence of mercaptobiphenyl chemisorption on surface carrier recombination rates. As a next step, the influence of pH-value and salt concentration upon the sensor device is discussed based on the results obtained from sensor conductance measurements in physiological solutions. A dependence of the device surface potential on both parameters due to surface charging is deduced. Model calculations applying Poisson-Boltzmann theory reveal as possible surface charging mechanisms either the adsorption of OH- ions on the surface, or the dissociation of OH groups in surface oxides. A comparison between simulation settings and physical device properties indicate the OH- adsorption as the most probable mechanism. In the second part of the present study the suitability of MBE grown III-V semiconductor structures for molecular electronics applications is examined. In doing so, a method to fabricate nanometer separated, coplanar, metallic electrodes based on the cleavage of a supporting AlGaAs-GaAs heterostructure is presented. This is followed

  15. Carbon doping of III-V compound semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Moll, Amy Jo [Univ. of California, Berkeley, CA (United States)


    Focus of the study is C acceptor doping of GaAs, since C diffusion coefficient is at least one order of magnitude lower than that of other common p-type dopants in GaAs. C ion implantation results in a concentration of free holes in the valence band < 10% of that of the implanted C atoms for doses > 1014/cm2. Rutherford backscattering, electrical measurements, Raman spectroscopy, and Fourier transform infrared spectroscopy were amonth the techniques used. Ga co-implantation increased the C activation in two steps: first, the additional radiation damage creates vacant As sites that the implanted C can occupy, and second, it maintains the stoichiometry of the implanted layer, reducing the number of compensating native defects. In InP, the behavior of C was different from that in GaAs. C acts as n-type dopant in the In site; however, its incorporation by implantation was difficult to control; experiments using P co-implants were inconsistent. The lattice position of inactive C in GaAs in implanted and epitaxial layers is discussed; evidence for formation of C precipitates in GaAs and InP was found. Correlation of the results with literature on C doping in III-V semiconductors led to a phenomenological description of C in III-V compounds (particularly GaAs): The behavior of C is controlled by the chemical nature of C and the instrinsic Fermi level stabilization energy of the material.

  16. Antisites in III-V semiconductors: Density functional theory calculations

    Energy Technology Data Exchange (ETDEWEB)

    Chroneos, A., E-mail: [Engineering and Innovation, The Open University, Milton Keynes MK7 6AA (United Kingdom); Tahini, H. A. [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); PSE Division, KAUST, Thuwal 23955-6900 (Saudi Arabia); Schwingenschlögl, U., E-mail: [PSE Division, KAUST, Thuwal 23955-6900 (Saudi Arabia); Grimes, R. W., E-mail: [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom)


    Density functional based simulation, corrected for finite size effects, is used to investigate systematically the formation of antisite defects in III-V semiconductors (III = Al, Ga, and In and V = P, As, and Sb). Different charge states are modelled as a function of the Fermi level and under different growth conditions. The formation energies of group III antisites (III{sub V}{sup q}) decrease with increasing covalent radius of the group V atom though not group III radius, whereas group V antisites (V{sub III}{sup q}) show a consistent decrease in formation energies with increase in group III and group V covalent radii. In general, III{sub V}{sup q} defects dominate under III-rich conditions and V{sub III}{sup q} under V-rich conditions. Comparison with equivalent vacancy formation energy simulations shows that while antisite concentrations are always dominant under stoichiometric conditions, modest variation in growth or doping conditions can lead to a significantly higher concentration of vacancies.

  17. Structure of metal-rich (001) surfaces of III-V compound semiconductors

    DEFF Research Database (Denmark)

    Kumpf, C.; Smilgies, D.; Landemark, E.


    The atomic structure of the group-III-rich surface of III-V semiconductor compounds has been under intense debate for many years, yet none of the models agrees with the experimental data available. Here we present a model for the three-dimensional structure of the (001)-c(8x2) reconstruction on In......(8 x 2) reconstructions of III-V semiconductor surfaces contain the same essential building blocks....

  18. Investigation of III-V semiconductor heterostructures for post-Si-CMOS applications (United States)

    Bhatnagar, Kunal

    Silicon complementary metal-oxide-semiconductor (CMOS) technology in the past few decades has been driven by aggressive device scaling to increase performance, reduce cost and lower power consumption. However, as devices are scaled below the 100 nm region, performance gain has become increasingly difficult to obtain by traditional scaling. As we move towards advanced technology nodes, materials innovation and physical architecture are becoming the primary enabler for performance enhancement in CMOS technology rather than scaling. One class of materials that can potentially result in improved electrical performance are III-V semiconductors, which are ideal candidates for replacing the channel in Si CMOS owing to their high electron mobilities and capabilities for band-engineering. This work is aimed towards the growth and characterization of III-V semiconductor heterostructures and their application in post-Si-CMOS devices. The two main components of this study include the integration of III-V compound semiconductors on silicon for tunnel-junction Esaki diodes, and the investigation of carrier transport properties in low-power III-V n-channel FETs under uniaxial strain for advanced III-V CMOS solutions. The integration of III-V compound semiconductors with Si can combine the cost advantage and maturity of the Si technology with the superior performance of III-V materials. We have demonstrated high quality epitaxial growth of GaAs and GaSb on Si (001) wafers through the use of various buffer layers including AlSb and crystalline SrTiO3. These GaSb/Si virtual substrates were used for the fabrication and characterization of InAs/GaSb broken-gap Esaki-tunnel diodes as a possible solution for heterojunction Tunnel-FETs. In addition, the carrier transport properties of InAs channels were evaluated under uniaxial strain for the potential use of strain solutions in III-V CMOS.

  19. III-V nitride semiconductors for solar hydrogen production (United States)

    Parameshwaran, Vijay; Gallinat, Chad; Enck, Ryan W.; Sampath, Anand V.; Shen, Paul H.; Kuykendall, Tevye; Aloni, Shaul; Wraback, Michael; Clemens, Bruce M.


    Photoelectrochemical cells are devices that can convert solar radiation to hydrogen gas through a water decomposition process. In this process, energy is converted from incident photons to the bonds of the generated H2 molecules. The solar radiation absorption, electron-hole pair splitting, and photoelectrolysis half reactions all occur in the vicinity of the electrode-electrolyte interface. As a result, engineering the electrode material and its interaction with the electrolyte is important in investigating and improving the energy conversion process in these devices. III-V nitride materials are promising candidates for photoelectrochemical energy applications. We demonstrate solar-to-hydrogen conversion in these cells using p-type GaN and n-type InGaN as a photocathode and photoanode material, respectively. Additionally, we demonstrate heteroepitaxial MOCVD growth of GaP on Si, enabling future work in developing GaPN as a photocathode material.

  20. Growth and Defect Characterization of Quantum Dot-Embedded III-V Semiconductors for Advanced Space Photovoltaics (United States)


    intermediate band, quantum dots, metamorphic III-V semiconductors, virtual substrates, defect spectroscopy, molecular beam epitaxy 16. SECURITY...AFRL-RV-PS- AFRL-RV-PS- TR-2014-0059 TR-2014-0059 GROWTH AND DEFECT CHARACTERIZATION OF QUANTUM DOT-EMBEDDED III-V SEMICONDUCTORS FOR ADVANCED...COVERED (From - To) 2 4 May 2012 – 06 Mar 2014 4. TITLE AND SUBTITLE Growth and Defect Characterization of Quantum Dot-Embedded III-V Semiconductors

  1. Theoretical models of ferromagnetic III-V semiconductors


    Jungwirth, T.; Sinova, Jairo; Kučera, J.; MacDonald, A. H.


    Recent materials research has advanced the maximum ferromagnetic transition temperature in semiconductors containing magnetic elements toward room temperature. Reaching this goal would make information technology applications of these materials likely. In this article we briefly review the status of work over the past five years which has attempted to achieve a theoretical understanding of these complex magnetic systems. The basic microscopic origins of ferromagnetism in the (III,Mn)V compoun...

  2. Characterization of Hydrogen Complex Formation in III-V Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Michael D


    Atomic hydrogen has been found to react with some impurity species in semiconductors. Hydrogenation is a methodology for the introduction of atomic hydrogen into the semiconductor for the express purpose of forming complexes within the material. Efforts to develop hydrogenation as an isolation technique for AlGaAs and Si based devices failed to demonstrate its commercial viability. This was due in large measure to the low activation energies of the formed complexes. Recent studies of dopant passivation in long wavelength (0.98 - 1.55m) materials suggested that for the appropriate choice of dopants much higher activation energies can be obtained. This effort studied the formation of these complexes in InP, This material is extensively used in optoelectronics, i.e., lasers, modulators and detectors. The experimental techniques were general to the extent that the results can be applied to other areas such as sensor technology, photovoltaics and to other material systems. The activation energies for the complexes have been determined and are reported in the scientific literature. The hydrogenation process has been shown by us to have a profound effect on the electronic structure of the materials and was thoroughly investigated. The information obtained will be useful in assessing the long term reliability of device structures fabricated using this phenomenon and in determining new device functionalities.

  3. Location of lanthanide impurity levels in the III-V semiconductor GaN

    NARCIS (Netherlands)

    Dorenbos, P.; Van der Kolk, E.


    Knowledge from lanthanide spectroscopy on wide band gap (6–10 eV) inorganic compounds is used to understand and predict optical and electronic properties of the lanthanides in the III-V semiconductor GaN. For the first time the location of the 4fn ground state energy of each divalent and trivalent l

  4. Surface chemistry and physics of III/V compound semiconductors (United States)

    Fu, Qiang

    The surface chemistry of gallium arsenide and indium phosphide has been investigated using infrared spectroscopy (IR), scanning tunneling microscopy (STM), and ab initio molecular cluster calculations. The work presented here provides the first theoretical framework for studying the reaction sites on compound semiconductor surfaces. These sites consist of dimers and threefold-coordinated atoms in the second layer. Stable clusters of gallium arsenide, i.e., GaxAsyHz, where x, y = 4, 5 and z = 11, 13, are those in which the arsenic dangling bonds are filled, while the gallium dangling bonds are empty. By contrast, stable clusters of indium phosphide, i.e., InxPyHz, where x, y = 4, 5 and z = 10, 11, 13, are those in which the phosphorous dangling bonds are either filled or half filled, and the indium dangling bonds are empty. The most important contribution of this work is the discovery of a new surface structure, the InP (001)-(2 x 1). The InP (2 x 1) is terminated with a complete layer of phosphorous dimers with a half-filled dangling bond on every other phosphorous atom. The half-filled orbital violate the electron counting model [Pashley, Phys. Rev. B 1989, 40, 10481], and indicate that many more reconstructions are possible on these surfaces than was originally thought. Excellent agreement is achieved between the molecular cluster calculations and the measured vibrational frequencies of adsorbed hydrogen and arsine on gallium arsenide and indium phosphide (001) surfaces. On both GaAs and InP, mono-hydrogen and di-hydrogen bonds are formed with the three-coordinate, group V atoms and dimers. Conversely, electron deficient bridging hydrides are produced on the group III dimers. These latter species occur in isolated or coupled structures involving two or three metal atoms. In addition, we have elucidated the kinetics and mechanism of arsine decomposition on gallium-rich GaAs (001). The combination of STM, IR, and ab initio molecular cluster calculations provides a

  5. Diffusion in Intrinsic and Highly Doped III-V Semiconductors

    CERN Multimedia

    Stolwijk, N


    %title\\\\ \\\\Diffusion plays a key role in the fabrication of semiconductor devices. The diffusion of atoms in crystals is mediated by intrinsic point defects. Investigations of the diffusion behaviour of self- and solute atoms on the Ga sublattice of gallium arsenide led to the conclusion that in intrinsic and n-type material charged Ga vacancies are involved in diffusion processes whereas in p-type material diffusion if governed by charged Ga self-interstitials. Concerning the As sublattice of gallium arsenide there is a severe lack of reliable diffusion data. The few available literature data on intrinsic GaAs are not mutually consistent. A systematic study of the doping dependence of diffusion is completely missing. The most basic diffusion process - self-diffusion of As and its temperature and doping dependence - is practically not known. For GaP a similar statement holds.\\\\ \\\\The aim of the present project is to perform a systematic diffusion study of As diffusion in intrinsic and doped GaAs and in GaP. P...

  6. Crystal-field spectra of 3d super n impurities in II-VI and III-V compound semiconductors. (United States)

    Allen, J. W.; Baranowski, J. M.; Pearson, G. L.


    Impurity crystal-field spectra in II-VI and III- V compound semiconductors used to predict unexplored systems spectra impurity crystal-field spectra in II-VI and III-V compound semiconductors used to predict unexplored systems spectra

  7. DLTS characterisation of defects in III-V compound semiconductors grown by MBE



    The interest in the growth of III-V compound semiconductors such as GaAs and AlGaAs on high index planes has increased tremendously over the last few years. The structural, optical and electrical properties III-V based structures are found to improve by, growing on (nil) planes. For example the amphoteric nature of silicon (Si) facilitates the Molecular Beam Epitaxy (MBE) growth of p-type GaAs/AlGaAs heterostructures on (311)A that have higher hole mobilities than those based on the conventio...

  8. Methods for forming group III-V arsenide-nitride semiconductor materials (United States)

    Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)


    Methods are disclosed for forming Group III--arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

  9. Generic technique to grow III-V semiconductor nanowires in a closed glass vessel

    Directory of Open Access Journals (Sweden)

    Kan Li


    Full Text Available Crystalline III-V semiconductor nanowires have great potential in fabrication of nanodevices for applications in nanoelectronics and optoelectronics, and for studies of novel physical phenomena. Sophisticated epitaxy techniques with precisely controlled growth conditions are often used to prepare high quality III-V nanowires. The growth process and cost of these experiments are therefore dedicated and very high. Here, we report a simple but generic method to synthesize III-V nanowires with high crystal quality. The technique employs a closed evacuated tube vessel with a small tube carrier containing a solid source of materials and another small tube carrier containing a growth substrate inside. The growth of nanowires is achieved after heating the closed vessel in a furnace to a preset high temperature and then cooling it down naturally to room temperature. The technique has been employed to grow InAs, GaAs, and GaSb nanowires on Si/SiO2 substrates. The as-grown nanowires are analyzed by SEM, TEM and Raman spectroscopy and the results show that the nanowires are high quality zincblende single crystals. No particular condition needs to be adjusted and controlled in the experiments. This technique provides a convenient way of synthesis of III-V semiconductor nanowires with high material quality for a wide range of applications.

  10. X-point deformation potentials of III-V semiconductors in a tight-binding approach (United States)

    Muñoz, M. C.; Armelles, G.


    The hydrostatic E1 and shear E2 deformation potentials of the III-V semiconductor compounds are calculated within a nearest-neighbor tight-binding approach. In the sp3s* parametrization, analytical expressions for both E1 and E2 are derived. The scaling law of the s*p interaction is modified in such a way that it provides deformation potentials at X in reasonable agreement with available experimental data. This phenomenological term takes into account the physical behavior of the actual excited states under strain and consequently, it allows us to describe accurately the dependence of the band-edge states under (001) biaxial strain.

  11. Phase transitions in Group III-V and II-VI semiconductors at high pressure (United States)

    Yu, S. C.; Liu, C. Y.; Spain, I. L.; Skelton, E. F.


    The structures and transition pressures of Group III-V and II-VI semiconductors and of a pseudobinary system (Ga/x/In/1-x/Sb) have been investigated. Results indicate that GaP, InSb, GaSb, GaAs and possible AlP assume Metallic structures at high pressures; a tetragonal, beta-Sn-like structure is adopted by only InSb and GaSb. The rocksalt phase is preferred in InP, InAs, AlSb, ZnO and ZnS. The model of Van Vechten (1973) gives transition pressures which are in good agreement with measured values, but must be refined to account for the occurrence of the ionic rocksalt structure in some compounds. In addition, discrepancies between the theoretical scaling values for volume changes at the semiconductor-to-metal transitions are observed.

  12. Implications of the Differential Toxicological Effects of III-V Ionic and Particulate Materials for Hazard Assessment of Semiconductor Slurries. (United States)

    Jiang, Wen; Lin, Sijie; Chang, Chong Hyun; Ji, Zhaoxia; Sun, Bingbing; Wang, Xiang; Li, Ruibin; Pon, Nanetta; Xia, Tian; Nel, André E


    Because of tunable band gaps, high carrier mobility, and low-energy consumption rates, III-V materials are attractive for use in semiconductor wafers. However, these wafers require chemical mechanical planarization (CMP) for polishing, which leads to the generation of large quantities of hazardous waste including particulate and ionic III-V debris. Although the toxic effects of micron-sized III-V materials have been studied in vivo, no comprehensive assessment has been undertaken to elucidate the hazardous effects of submicron particulates and released III-V ionic components. Since III-V materials may contribute disproportionately to the hazard of CMP slurries, we obtained GaP, InP, GaAs, and InAs as micron- (0.2-3 μm) and nanoscale (materials that could appear in slurries. This finding is of importance for considering how to deal with the hazard potential of CMP slurries.

  13. Engineering the cell-semiconductor interface: a materials modification approach using II-VI and III-V semiconductor materials. (United States)

    Bain, Lauren E; Ivanisevic, Albena


    Developing functional biomedical devices based on semiconductor materials requires an understanding of interactions taking place at the material-biosystem interface. Cell behavior is dependent on the local physicochemical environment. While standard routes of material preparation involve chemical functionalization of the active surface, this review emphasizes both biocompatibility of unmodified surfaces as well as use of topographic features in manipulating cell-material interactions. Initially, the review discusses experiments involving unmodified II-VI and III-V semiconductors - a starting point for assessing cytotoxicity and biocompatibility - followed by specific surface modification, including the generation of submicron roughness or the potential effect of quantum dot structures. Finally, the discussion turns to more recent work in coupling topography and specific chemistry, enhancing the tunability of the cell-semiconductor interface. With this broadened materials approach, researchers' ability to tune the interactions between semiconductors and biological environments continues to improve, reaching new heights in device function.

  14. III-V Metal-Oxide-Semiconductor Field-Effect Transistors with High κ Dielectrics (United States)

    Hong, Minghwei; Kwo, J. Raynien; Tsai, Pei-chun; Chang, Yaochung; Huang, Mao-Lin; Chen, Chih-ping; Lin, Tsung-da


    Research efforts on achieving low interfacial density of states (Dit) as well as low electrical leakage currents on GaAs-based III-V compound semiconductors are reviewed. Emphasis is placed on ultra high vacuum (UHV) deposited Ga2O3(Gd2O3) and atomic layer deposition (ALD)-Al2O3 on GaAs and InGaAs. Ga2O3(Gd2O3), the novel oxide, which was electron-beam evaporated from a gallium-gadolinium-garnet target, has, for the first time, unpinned the Fermi level of the oxide/GaAs heterostructures. Interfacial chemical properties and band parameters of valence band offsets and conduction band offsets in the oxides/III-V heterostructures are studied and determined using X-ray photoelectron spectroscopy and electrical leakage transport measurements. The mechanism of III-V surface passivation is discussed. The mechanism of Fermi-level unpinning in ALD-Al2O3 ex-situ deposited on InGaAs were studied and unveiled. Systematic heat treatments under various gases and temperatures were studied to achieve low leakage currents of 10-8-10-9 A/cm2 and low Dit’s in the range of (4--9)× 1010 cm-2 eV-1 for Ga2O3(Gd2O3) on InGaAs. By removing moisture from the oxide, thermodynamic stability of the Ga2O3(Gd2O3)/GaAs heterostructures was achieved with high temperature annealing, which is needed for fabricating inversion-channel metal-oxide-semiconductor filed-effect transistors (MOSFET’s). The oxide remains amorphous and the interface remains intact with atomic smoothness and sharpness. Device performances of inversion-channel and depletion-mode III-V MOSFET’s are reviewed, again with emphasis on the devices using Ga2O3(Gd2O3) as the gate dielectric.

  15. A model of axial heterostructure formation in III-V semiconductor nanowires (United States)

    Dubrovskii, V. G.


    A kinetic model of the formation of axial heterostructures in nanocrystalline wires (nanowires, NWs) of III-V semiconductor compounds growing according to the vapor-liquid-solid (VLS) mechanism is proposed. A general system of nonstationary equations for effective fluxes of two elements of the same group (e.g., group III) is formulated that allows the composition profile of a heterostructure to be calculated as a function of the coordinate and epitaxial growth conditions, including the flux of a group V element. Characteristic times of the composition relaxation, which determine the sharpness of the heteroboundary (heterointerface), are determined in the linear approximation. A temporal interruption (arrest) of fluxes during the switching of elements for a period exceeding these relaxation times must increase sharpness of the heteroboundary. Model calculations of the composition profile in a double GaAs/InAs/GaAs axial heterostructure have been performed for various NW radii.

  16. High resolution electron energy loss spectroscopy of narrow gap III-V semiconductor surfaces and interfaces

    CERN Document Server

    Veal, T D


    The electronic properties of n-type narrow gap III-V semiconductor surfaces and interfaces are investigated using high-resolution electron-energy-loss spectroscopy (HREELS). Changing the incident electron energy, alters the wave-vector transfer parallel to the surface, allowing the probing depth to be varied over typical space-charge layer widths (100 - 2000 A). Semi-classical dielectric theory simulations of the HREEL spectra are performed to extract quantitative information from the probing energy-dependence of the surface plasmon and phonon peaks. The plasma frequency used in the simulations is related to the electron concentration and effective mass using the Kane model of the non-parabolic conduction band. Space-charge layer parameters are obtained by comparing calculated smooth charge profiles with the histogram profiles that are used in the simulations. Complementary experimental techniques are employed to correlate the reconstruction, chemical composition and morphology of the surface with the electro...

  17. Spin Manipulation through geometric phase in III-V semiconductor quantum dots (United States)

    Prbahakar, Sanjay; Melnik, Roderick


    A more robust technique is proposed to flip the spin completely through geometric phase in III-V semiconductor quantum dots (QDs). We transport the QDs adiabatically in a closed loop along the circular trajectory in the plane of two dimensional electron gas with the application of time dependent gate controlled electric fields and investigate the manipulation of Berry phase with the spin-orbit couplings. Here we show that both the Rashba and the Dresselhaus couplings are present for inducing a phase necessary for spin flip. If one of them is absent, the induced phase is trivial and irrelevant for spin-flip (Phys. Rev. B 89, 245310 (2014), Applied Physics Letters 104, 142411 (2014)). We acknowledge the funding agency: Natural Sciences and Engineering Research Council of Canada and Canada Research Chair Program.

  18. Surfaces of III-V semiconductors studied by scanning tunneling microscopy and scanning luminescence (United States)

    Chizhov, Ilya Yu

    The investigation of semiconductor surfaces on an atomic scale is of key importance for research areas such as the growth of thin films and low-dimensional objects by epitaxial techniques. Surfaces of III-V semiconductors, especially GaAs(001) surface, hold a central position in semiconductor surface science due to their extremely wide use in the growth of heterostructure-based electronic and optoelectronic devices. This work describes the results of experimental studies of (001) surfaces of two III-V semiconductors, GaAs and InAs, using scanning tunneling microscopy (STM) and scanning tunneling luminescence (STL). For STL studies an optical detection system consisting of an optical spectrometer (replacable by a photomultiplier tube), electronics, an IBM PC computer and acquisition software has been added to an existing STM (Omicron). The system is capable of recording luminescence images of surfaces and the acquisition of optical spectra of STM-induced luminescence. Application of STL to GaAs(001) surfaces has revealed that atomic-scale features, such as steps, domain boundaries etc., do not give any contrast in luminescence images, while larger objects, such as arsenic islands, do produce a pronounced contrast. The work in STL has helped to identify several key problems that have to be solved in order to make STL a valuable analytical technique. The STM studies of reconstructions on the GaAs(001) surface, which has a fairly complicated phase diagram, have concentrated on two major phase transitions, from As-rich c(4× 4) to As-rich (2× 4) phase and from As-rich (2× 4) to Ga-rich (4× 2) phase. The first transition has been found to proceed through an intermediate (4× 3)/c(4× 6) phase which has been previously identified as having (2× 3) symmetry. The second transition has been found to involve the formation of (3× 6) and (4× 6) multi-domain phases. The local structure and composition of these phases have been analyzed in detail and a comprehensive dynamic

  19. III-V semiconductor nano-resonators-a new strategy for passive, active, and nonlinear all-dielectric metamaterials

    CERN Document Server

    Liu, Sheng; Reno, John L; Sinclair, Michael B; Brener, Igal


    Metamaterials comprising assemblies of dielectric resonators have attracted much attention due to their low intrinsic loss and isotropic optical response. In particular, metasurfaces made from silicon dielectric resonators have shown desirable behaviors such as efficient nonlinear optical conversion, spectral filtering and advanced wave-front engineering. To further explore the potential of dielectric metamaterials, we present all-dielectric metamaterials fabricated from epitaxially grown III-V semiconductors that can exploit the high second-order optical susceptibilities of III-V semiconductors, as well as the ease of monolithically integrating active/gain media. Specifically, we create GaAs nano-resonators using a selective wet oxidation process that forms a low refractive index AlGaO (n~1.6) under layer similar to silicon dielectric resonators formed using silicon-on-insulator wafers. We further use the same fabrication processes to demonstrate multilayer III-V dielectric resonator arrays that provide us w...

  20. Superconductivity in Group III-V Semiconductor AlN Under High Pressure

    Directory of Open Access Journals (Sweden)

    G. Selva Dancy


    Full Text Available The electronic properties of cubic zinc blende type group III-V semiconductor AlN under pressure is studied using full potential linear muffin-tin orbital (FP-LMTO method. At normal pressure, AlN is an indirect bandgap semiconductor with band gap value 4.56 eV. When the pressure is increased, there is enhanced overlapping between the wave functions of the neighboring atoms. As a result the widths of the valence and empty conduction bands increase. These changes lead to the narrowing and indirect closing of the band gaps in AlN (metallization. On further increase of pressure, AlN becomes a superconductor and AlN comes under the class of electron-phonon-mediated high pressure superconductors. The superconducting transition temperatures (Tc of AlN are obtained as a function of pressure for the CsCl structure. It is also confirmed that the metallization, structural phase transition and onset of superconductivity do not occur simultaneously in this compound. DOI:

  1. Electroless Deposition of III-V Semiconductor Nanostructures from Ionic Liquids at Room Temperature. (United States)

    Lahiri, Abhishek; Borisenko, Natalia; Olschewski, Mark; Gustus, René; Zahlbach, Janine; Endres, Frank


    Group III-V semiconductor nanostructures are important materials in optoelectronic devices and are being researched in energy-related fields. A simple approach for the synthesis of these semiconductors with well-defined nanostructures is desired. Electroless deposition (galvanic displacement) is a fast and versatile technique for deposition of one material on another and depends on the redox potentials of the two materials. Herein we show that GaSb can be directly synthesized at room temperature by galvanic displacement of SbCl3 /ionic liquid on electrodeposited Ga, on Ga nanowires, and also on commercial Ga. In situ AFM revealed the galvanic displacement process of Sb on Ga and showed that the displacement process continues even after the formation of GaSb. The bandgap of the deposited GaSb was 0.9±0.1 eV compared to its usual bandgap of 0.7 eV. By changing the cation in the ionic liquid, the redox process could be varied leading to GaSb with different optical properties.

  2. Heats of formation of binary semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, V.; Sastry, B.S.R. [Department of Electronics and Instrumentation Indian School of Mines, Dhanbad 826 004 (India)


    Heats of formation of tetrahedrally coordinated II-VI and III-V groups of binary semiconductors have been calculated using plasmon energy data. Two simple relations between plasmon energy and heats of formation have been proposed. One is based on spectroscopic model of Phillips and Van Vechten and other is based on the best-fit data of heats of formation. The calculated values of heats of formation from both the equations are compared with the experimental values and the values reported by earlier workers. A fairly good agreement has been obtained between them. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Nano-photonics in III-V semiconductors for integrated quantum optical circuits (United States)

    Wasley, Nicholas Andrew

    This thesis describes the optical spectroscopic measurements of III-V semiconductors used to investigate a number of issues related to the development of integrated quantum optical circuits. The disorder-limited propagation of photons in photonic crystal waveguides in the slow-light regime is investigated. The analysis of Fabry-Perot resonances is used to map the mode dispersion and extract the photon localisation length. Andersonlocalised modes are observed at high group indices, when the localisation lengths are shorter than the waveguide lengths, consistent with the Fabry-Perot analysis. A spin-photon interface based on two orthogonal waveguides is introduced, where the polarisation emitted by a quantum dot is mapped to a path-encoded photon. Operation is demonstrated by deducing the spin using the interference of in-plane photons. A second device directly maps right and left circular polarisations to anti-parallel waveguides, surprising for a non-chiral structure but consistent with an off-centre dot. Two dimensional photonic crystal cavities in GaInP and full control over the spontaneous emission rate of InP quantum dots is demonstrated by spectrally tuning the exciton emission energy into resonance with the fundamental cavity mode. Fourier transform spectroscopy is used to investigate the short coherence times of InP quantum dots in GaInP photonic crystal cavities. Additional technological developments are also presented including a quantum dot registration technique, electrical tuning of quantum dot emission and uniaxial strain tuning of H1 cavity modes.

  4. Interface formation between hydrocarbon ring molecules and III-V semiconductor surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Passmann, Regina


    In this work a systematical study to investigate the adsorption structures of small hydrocarbon ring shaped molecules on III-V semiconductor surfaces with Photo-Emission Spectroscopy (PES), Reflectance Anisotropy Spectroscopy (RAS), Scanning Tunneling Microscopy (STM) as well as Low Electron Energy Diffraction (LEED) was performed. To investigate the influence of the surface structure in detail the surface dimer configuration to the adsorption process of organic molecules GaAs(001) surfaces, the c(4 x 4), the (2 x 4) and the (4 x 2) have been investigated as well as the adsorption of cyclopentene on the InP(001)(2 x 4) reconstructed surface. In the direct comparison it is shown that cyclopentene bonds to the InP(001)(2 x 4) surface via a cycloaddition like reaction. During this adsorption the double bond splits which is in contrast to the adsorption of cyclopentene on the GaAs(001) surfaces. Therefrom it is concluded that the surface geometry has an influence on the resulting adsorption structure. In order to investigate the influence of the intra-molecular double bonds, cyclopentene (one double bond), 1,4-cyclohexadiene (two double bonds) and benzene (three double bonds) were used for the characterization of the interface formation. With the investigations on the GaAs(001) reconstructed surfaces it was shown that a dependency of the bonding configuration on the intra-molecular double bonds exists. During the adsorption of cyclopentene no evidence was found that the double bond has to be involved in the interface formation while during the adsorption of 1,4-cyclohexadiene and benzene the double bonds are involved. Furthermore it was found that a bonding to As atoms of the surface is more likely than a bonding to Ga atoms. (orig.)

  5. Phenomenological survey on the potential profile evolution in III-V binary compounds

    Directory of Open Access Journals (Sweden)

    Alejandro Mendoza Álvarez


    Full Text Available En este artículo se presenta el cambio en el perfil de eficacia potencial de algunos compuestos cuando el bandmixing de huecos ligeros y pesados se altera. Se obtuvieron mediante la aplicación de este teorema generalizado Shur a un problema de valores propios cuadrática obtenidos a partir de un sistema con N ecuaciones de segundo orden, junto en el contexto de la aproximación de masa efectiva multibanda. Se consideraron los valores de energía incidente que fue menor, igual y superior a la altura de la barrera de dispersión potencial de diferentes compuestos de semiconductores III-V binario. La mayoría de las propiedades estándar de los compuestos binarios en este estudio están garantizados, pero no todos los materiales que elegimos, han puesto de manifiesto la evolución que se espera en su perfil de potencial efectivo: algunos de los que constituyen los pozos cuánticos (QW en aplicaciones tecnológicas sólo convertirse en efectiva barrera (B las conductas de los agujeros de luz (LH cuando están en la energía incidente diferente (E se extiende y bandmixing diferentes presentes. Ninguno de los compuestos que constituyen barreras para las aplicaciones tecnológicas en este estudio se convierte en eficaz comportamientos QW válido tanto para la LH y HH. Sorprendentemente, todos los compuestos en este estudio que constituyen barreras estándar en las aplicaciones tecnológicas, las transiciones presente desde CS a B para la LH en el rango donde el valor de E es mayor que la altura de la barrera.

  6. Theory of band gap bowing of disordered substitutional II-VI and III-V semiconductor alloys



    For a wide class of technologically relevant compound III-V and II-VI semiconductor materials AC and BC mixed crystals (alloys) of the type A(x)B(1-x)C can be realized. As the electronic properties like the bulk band gap vary continuously with x, any band gap in between that of the pure AC and BC systems can be obtained by choosing the appropriate concentration x, granted that the respective ratio is miscible and thermodynamically stable. In most cases the band gap does not vary linearly with...

  7. Examination of the Ion Beam Response of III-V Semiconductor Substrates (United States)

    Grossklaus, Kevin A.

    This work examines the response of the III-V materials to ion beam irradiation in a series of four experimental studies and describes the observed results in terms of the fundamental materials processes and properties that control ion-induced change in those compounds. Two studies investigate the use of Ga+ focused ion beam (FIB) irradiation of III-V substrate materials to create nanostructures. In the first, the creation of FIB induced group III nanodots on GaAs, InP, InAs, and AlAs is studied. The analysis of those results in terms of basic material properties and a simple nanodot growth model represents the first unified investigation of the fundamental processes that drive the nanodot forming behavior of the III-V compounds. The second nanostructure formation study reports the discovery and characterization of unique spike-like InAs nanostructures, termed "nanospikes," which may be useful for nanoscale electronic or thermoelectric applications. A novel method for controlling nanospike formation using InAs/InP heterostructures and film pre-patterning is developed, and the electrical properties of these ion erosion created nanostructures are characterized by in-situ TEM nanoprobe testing in a first-of-its-kind examination. The two remaining studies examine methods for using ion beam modification of III-V substrates to accommodate lattice-mismatched film growth with improved film properties. The first examines the effects of film growth on a wide range of different FIB created 3-D substrate patterns, and finds that 3-D surface features and patterns significantly alter film morphology and that growth on or near FIB irradiated regions does not improve film threading defect density. The second substrate modification study examines broad beam ion pre-implantation of GaAs wafers before InGaAs film growth, and is the first reported study of III-V substrate pre-implantation. Ar + pre-implantation was found to enhance the formation of threading defects in InGaAs films and

  8. Laser Induced Chemical Vapor Phase Epitaxial Growth of III-V semiconductor Films (United States)


    temperatures for the preparation and crystal growth of semiconductors . During the first phase of this program at Southern Methodist University, the epitaxial...approach to the preparation of device-quality 4 semiconductor films of controlled electrical and stru -.tural propierties . The excitation of reaction...temperatures for the preparation and crystal growth of semiconductors . The vapors of essentially all metalorganic compounds and group V hydrides are colorless

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


    AFRL-AFOSR-VA-TR-2015-0251 MULTICOLOR (UV-IR) PHOTODETECTORS BASED ON LATTICE MATCHED 6.1A II/IV AND III/V SEMICONDUCTORS Yong-Hang Zhang ARIZONA...14-05-2015 4. TITLE AND SUBTITLE Multicolor (UV-IR) Photodetectors Based on Lattic Matched 61A IIIV and IIIV Semiconductors 5a. CONTRACT NUMBER 5b...infrared multi-color photodetector based on II-VI and III-V semiconductors . This photodetector consists of a newly-proposed CdTe/ZnTe/CdTe nBn sub

  10. Enhanced amplified spontaneous emission in III-V semiconductor photonic crystal waveguides

    DEFF Research Database (Denmark)

    Ek, Sara; Schubert, Martin; Yvind, Kresten;


    We experimentally demonstrate enhanced amplified spontaneous emission in the slow light regime of an active photonic crystal waveguide slab. This promises great opportunities for future devices such as miniaturized semiconductor optical amplifiers and mode-locked lasers.......We experimentally demonstrate enhanced amplified spontaneous emission in the slow light regime of an active photonic crystal waveguide slab. This promises great opportunities for future devices such as miniaturized semiconductor optical amplifiers and mode-locked lasers....

  11. Scattering amplitudes and static atomic correction factors for the composition-sensitive 002 reflection in sphalerite ternary III-V and II-VI semiconductors. (United States)

    Schowalter, M; Müller, K; Rosenauer, A


    Modified atomic scattering amplitudes (MASAs), taking into account the redistribution of charge due to bonds, and the respective correction factors considering the effect of static atomic displacements were computed for the chemically sensitive 002 reflection for ternary III-V and II-VI semiconductors. MASAs were derived from computations within the density functional theory formalism. Binary eight-atom unit cells were strained according to each strain state s (thin, intermediate, thick and fully relaxed electron microscopic specimen) and each concentration (x = 0, …, 1 in 0.01 steps), where the lattice parameters for composition x in strain state s were calculated using continuum elasticity theory. The concentration dependence was derived by computing MASAs for each of these binary cells. Correction factors for static atomic displacements were computed from relaxed atom positions by generating 50 × 50 × 50 supercells using the lattice parameter of the eight-atom unit cells. Atoms were randomly distributed according to the required composition. Polynomials were fitted to the composition dependence of the MASAs and the correction factors for the different strain states. Fit parameters are given in the paper.

  12. On the ferromagnetic exchange in Mn-doped III-V semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, V.A.; Krstajic, P.M.; Peeters, F.M.; Fleurov, V.; Kikoin, K


    We propose a microscopic model for double exchange in GaAs:Mn, GaP:Mn which is based on the interaction between the transition metal impurities and the heavy holes of host semiconductor. The kinematic exchange is derived and the Curie temperature is calculated which agrees with recent experiments.

  13. III-V microelectronics

    CERN Document Server

    Nougier, JP


    As is well known, Silicon widely dominates the market of semiconductor devices and circuits, and in particular is well suited for Ultra Large Scale Integration processes. However, a number of III-V compound semiconductor devices and circuits have recently been built, and the contributions in this volume are devoted to those types of materials, which offer a number of interesting properties. Taking into account the great variety of problems encountered and of their mutual correlations when fabricating a circuit or even a device, most of the aspects of III-V microelectronics, from fundamental p

  14. Discrimination of defects in III-V semiconductors by positron lifetime distribution

    CERN Document Server

    Chen, Z Q; Wang, S J


    In this paper, the numerical Laplace inversion technique and maximum entropy method are utilized to extract continuous positron lifetime distribution in semiconductors. The result is used to discriminate the native vacancy-type defects in as-grown GaAs and In P with different conduction type. Direct evidence of shallow positron traps were also observed in ion-implanted p-In P. It is demonstrated that the lifetime distribution can give us more detailed information on the native defects.

  15. Hybrid integration of III-V semiconductor lasers on silicon waveguides using optofluidic microbubble manipulation (United States)

    Jung, Youngho; Shim, Jaeho; Kwon, Kyungmook; You, Jong-Bum; Choi, Kyunghan; Yu, Kyoungsik


    Optofluidic manipulation mechanisms have been successfully applied to micro/nano-scale assembly and handling applications in biophysics, electronics, and photonics. Here, we extend the laser-based optofluidic microbubble manipulation technique to achieve hybrid integration of compound semiconductor microdisk lasers on the silicon photonic circuit platform. The microscale compound semiconductor block trapped on the microbubble surface can be precisely assembled on a desired position using photothermocapillary convective flows induced by focused laser beam illumination. Strong light absorption within the micro-scale compound semiconductor object allows real-time and on-demand microbubble generation. After the assembly process, we verify that electromagnetic radiation from the optically-pumped InGaAsP microdisk laser can be efficiently coupled to the single-mode silicon waveguide through vertical evanescent coupling. Our simple and accurate microbubble-based manipulation technique may provide a new pathway for realizing high precision fluidic assembly schemes for heterogeneously integrated photonic/electronic platforms as well as microelectromechanical systems.

  16. A survey of ohmic contacts to III-V compound semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Baca, A.G.; Zolper, J.C.; Briggs, R.D. [Sandia National Labs., Albuquerque, NM (United States); Ren, F. [Lucent Technologies, Murray Hill, NJ (United States); Pearton, S.J. [Univ. of Florida, Gainesville, FL (United States)


    A survey of ohmic contact materials and properties to GaAs, InP, GaN will be presented along with critical issues pertaining to each semiconductor material. Au-based alloys (e.g., GeAuNi for n-type GaAs) are the most commonly used contacts for GaAs and InP materials for both n- and p-type contacts due to the excellent contact resistivity, reliability, and usefulness over a wide range of doping levels. Research into new contacting schemes for these materials has focused on addressing limitations of the conventional Au-alloys in thermal stability, propensity for spiking, poor edge definition, and new approaches for a non-alloyed contact. The alternative contacts to GaAs and InP include alloys with higher temperature stability, contacts based on solid phase regrowth, and contacts that react with the substrate to form lower bandgap semiconductors alloys at the interface. A new area of contact studies is for the wide bandgap group III-Nitride materials. At present, low resistivity ohmic contact to p-type GaN has not been obtained primarily due to the large acceptor ionization energy and the resultant difficulty in achieving high free hole concentrations at room temperature. For n-type GaN, however, significant progress has been reported with reactive Ti-based metalization schemes or the use of graded InGaN layers. The present status of these approaches will be reviewed.

  17. Magnetic properties in III-V diluted magnetic semiconductor quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Dakhlaoui, H. [Departement de Physique, Faculte des Sciences de Bizerte, 7000 (Tunisia); Jaziri, S. [Departement de Physique, Faculte des Sciences de Bizerte, 7000 (Tunisia)]. E-mail:


    Spin injection in low-dimensional semiconductors have a great potential to be used in magnetoelectronics and spintronics. In our work we analyze the electronic properties of the hole gas formed in Ga{sub 1-x}Mn{sub x}As/GaAs/Ga{sub 1-x}Mn{sub x}As heterostructures. We find that there is an RKKY-type exchange coupling between the magnetic layers that oscillates between ferromagnetic and antiferromagnetic as a function of the different parameters of the problem. As an example we calculate the spin-dependent hole density, the polarization and the coupling energy, using an efficient self-consistent procedure to solve simultaneously the Schroedinger and Poisson equations, taking into account the interaction with Mn magnetic moments. Our results indicate that the coupling energy also oscillates in terms of the band offset V{sub w} which describes the difference in electronegativity between the Mn and GaAs atoms.

  18. Bell states generation on a III-V semiconductor chip at room temperature

    CERN Document Server

    Orieux, Adeline; Lemaître, Aristide; Filloux, Pascal; Favero, Ivan; Leo, Giuseppe; Coudreau, Thomas; Keller, Arne; Milman, Pérola; Ducci, Sara


    We demonstrate the generation of polarization-entangled photon pairs at room temperature and telecom wavelength in a AlGaAs semiconductor waveguide. The source is based on spontaneous parametric down conversion with a counterpropagating phase-matching scheme. The quality of the two-photon state is assessed by the reconstruction of the density matrix giving a raw fidelity to a Bell state of 0.83; a theoretical model, taking into account the experimental parameters, provides ways to understand and control the amount of entanglement. Its compatibility with electrical injection, together with the high versatility of the generated two-photon state, make this source an attractive candidate for completely integrated quantum photonics devices.

  19. Virtual crystal description of III-V semiconductor alloys in the tight binding approach (United States)

    Nestoklon, M. O.; Benchamekh, R.; Voisin, P.


    We propose a simple and effective approach to construct the empirical tight-binding parameters of ternary alloys in the virtual crystal approximation. This combines a new, compact formulation of the strain parameters and a linear interpolation of the Hamiltonians of binary materials strained to the alloy equilibrium lattice parameter. We show that it is possible to obtain a perfect description of the bandgap bowing of ternary alloys in the InGaAsSb family of materials. Furthermore, this approach is in a good agreement with supercell calculations using the same set of parameters. This scheme opens a way for atomistic modeling of alloy-based quantum wells and quantum wires without extensive supercell calculations.

  20. Growth and Characterization of III-V Semiconductors for Device Applications (United States)

    Williams, Michael D.


    The research goal was to achieve a fundamental understanding of the physical processes occurring at the surfaces and interfaces of epitaxially grown InGaAs/GaAs (100) heterostructures. This will facilitate the development of quantum well devices for infrared optical applications and provide quantitative descriptions of key phenomena which impact their performance. Devices impacted include high-speed laser diodes and modulators for fiber optic communications at 1.55 micron wavelengths and intersub-band lasers for longer infrared wavelengths. The phenomenon of interest studied was the migration of indium in InGaAs structures. This work centered on the molecular beam epitaxy reactor and characterization apparatus donated to CAU by AT&T Bell Laboratories. The material characterization tool employed was secondary ion mass spectrometry. The training of graduate and undergraduate students was an integral part of this program. The graduate students received a thorough exposure to state-of-the-art techniques and equipment for semiconductor materials analysis as part of the Master''s degree requirement in physics. The undergraduates were exposed to a minority scientist who has an excellent track record in this area. They also had the opportunity to explore surface physics as a career option. The results of the scientific work was published in a refereed journal and several talks were presented professional conferences and academic seminars.

  1. Intersubband transitions in III-V semiconductors for novel infrared optoelectronic devices (United States)

    Hossain, Mohammed Imrul

    Intersubband transitions (ISBTs) in the conduction band (CB) of semiconductor multiple quantum wells (QW) have led to devices, like quantum-well infrared photodetectors and quantum cascade lasers (QCL). Due to the complexities related to the valence band (VB), hole ISBTs have not been explored as intensively as their electronic counterparts. Absorption and photoluminescence due to ISBT in the VB have been reported for p-type Si-SiGe QWs but this material system suffers from significant challenges associated with the built-in strain of these lattice mismatched materials. The GaAs/AlGaAs material system is virtually strain-free and quite mature. We are investigating the properties of bound-to-bound inter-valence subband transitions in GaAs QWs with high Al composition barriers for mid-infrared emitters. Hole ISBTs are interesting because the polarization of the light emitted in heavy-to-light hole transitions is not restricted to the perpendicular of the quantum wells (unlike electron ISBTs in the CB due to selection rules), therefore surface emitting QCLs and ultimately vertical-cavity surface emitting devices are possible using these transitions. Moreover the valence-band offset for pure GaAs and AlAs is comparable with the conduction-band offset in the traditional InGaAs/InAlAs lattice matched to InP system. Very recently we have observed strong heavy to light hole absorption and heavy to heavy hole electroluminescence from ridge waveguide structures in the mid infra-red range. We are also investigating dual wavelength mid infra-red QCLs in the InGaAs/InAlAs system lattice matched to InP. This device may be useful in applications like differential absorption lidar where light has to be evaluated and compared at two different frequencies for environmental sensing application. Most approaches to multi-wavelength QCL operation involve the use of heterogeneous cascades. Our design involves a single type of active region, emitting at two widely different wavelengths in

  2. Luminescence properties or rare earth doped III-V and II- VI semiconductors (United States)

    Alshawa, Amer Kamal

    Two novel step impact optical devices have been proposed by H. J. Lozykowski, the step impact electroluminescence device (SIED) and the step photon amplifier converter (SPAC). The realization of the proposed devices requires systematic study of the optical properties of rare earth doped semiconductors. The experimental data is explained using a kinetics model of energy transfer from the host lattice to the localized core excited states of rare earth isoclectronic structured traps (REI-trap). The numerically simulated lun-finescence rise and decay times show a good general quantitative agreement with experimental data, over a wide range of generation rates. A new quenching mechanism of ytterbium luminescence involving Yb and Fe ions is proposed. Detailed experimental and theoretical studies of the electrolurninescence excitation mechanism of Yb3+ in InP are presented. The electroluminescence (EL) spectra and the kinetics of Yb implanted InP are investigated under pulsed and dc excitations at different temperatures. The plot of natural logarithm (In) of I versus V-1/2 indicates that the direct impact excitation mechanism is a dominant process. A systematic study of the effect of oxygen on ytterbium 4f-4f emission by coimplanting Yb and O into InP is performed. The PL spectra and kinetic processes of InP: Yb and InP: (Yb+O) are recorded as a function of temperature, excitation intensity and annealing temperature and duration. No luminescence was observed after oxygen co-implantation and that is because the exciton bound to a YbIn-OP complex center will not have sufficient energy to excite the core Yb 4f electrons. The photoluminescence spectra and kinetics of Nd- and Yb-implanted CdS were investigated as a function of excitation intensity and temperature. The ac electroluminescence of thulium doped ZnS embedded in boric acid matrix was investigated as a function of voltage, frequency and temperature. The plot of In(I) versus V-1/2 shows a straight line characteristic

  3. Tunable Optical Phenomena and Carrier Recombination Dynamics in III-V Semiconductor Nanostructures (United States)

    Kumar Thota, Venkata Ramana

    Semiconductor nanostructures such as quantum dots, quantum wires and quantum wells have gained significant attention in the scientific community due to their peculiar properties, which arise from the quantum confinement of charge carriers. In such systems, confinement plays key role and governs the emission spectra. With the advancements in growth techniques, which enable the fabrication of these nanostructured devices with great precision down to the atomic scale, it is intriguing to study and observe quantum mechanical effects through light-matter interactions and new physics governed by the confinement, size, shape and alloy composition. The goal is to reduce the size of semiconductor bulk material to few nanometers, which in turn localizes the charge carriers inside these structures such that the spin associated with them is used to carry and process information within ultra-short time scales. The main focus of this dissertation is the optical studies of quantum dot molecule (QDM) systems. A system where the electrons can tunnel between the two dots leading to observable tunneling effects. The emission spectra of such system has been demonstrated to have both intradot transitions (electron-hole pair residing in the same dot) and interdot transitions (electron-hole pair participating in the recombination origin from different dots). In such a system, it is possible to apply electric field such that the wavefunction associated with the charge carriers can be tuned to an extent of delocalizing between the two dots. This forms the first project of this dissertation, which addresses the origin of the fine structure splitting in the exciton-biexciton cascade. Moreover, we also show how this fine structure can be tuned in the quantum dot molecule system with the application of electric field along the growth direction. This is demonstrated through high resolution polarization dependent photoluminescence spectroscopy on a single QDM, which was described in great detail

  4. Two Dimensional Effective Electron Mass at the Fermi Level in Quantum Wells of III-V, Ternary and Quaternary Semiconductors. (United States)

    Chakrabarti, S; Chatterjee, B; Debbarma, S; Ghatak, K P


    In this paper we study the influence of strong electric field on the two dimensional (2D)effective electron mass (EEM) at the Fermi level in quantum wells of III-V, ternary and quaternary semiconductors within the framework of k x p formalism by formulating a new 2D electron energy spectrum. It appears taking quantum wells of InSb, InAs, Hg(1-x)Cd(x)Te and In(1-x)Ga(x)As(1-y)P(y) lattice matched to InP as examples that the EEM increases with decreasing film thickness, increasing electric field and increases with increasing surface electron concentration exhibiting spikey oscillations because of the crossing over of the Fermi level by the quantized level in quantum wells and the quantized oscillation occurs when the Fermi energy touches the sub-band energy. The electric field makes the mass quantum number dependent and the oscillatory mass introduces quantum number dependent mass anisotropy in addition to energy. The EEM increases with decreasing alloy composition where the variations are totally band structure dependent. Under certain limiting conditions all the results for all the cases get simplified into the well-known parabolic energy bands and thus confirming the compatibility test. The content of this paper finds three applications in the fields of nano-science and technology.

  5. Atomic scale images of acceptors in III-V semiconductors. Band bending, tunneling paths and wave functions

    Energy Technology Data Exchange (ETDEWEB)

    Loth, S.


    This thesis reports measurements of single dopant atoms in III-V semiconductors with low temperature Scanning Tunneling Microscopy (STM) and Scanning Tunneling Spectroscopy (STS). It investigates the anisotropic spatial distribution of acceptor induced tunneling processes at the {l_brace}110{r_brace} cleavage planes. Two different tunneling processes are identified: conventional imaging of the squared acceptor wave function and resonant tunneling at the charged acceptor. A thorough analysis of the tip induced space charge layers identifies characteristic bias windows for each tunnel process. The symmetry of the host crystal's band structure determines the spatial distribution of the tunneling paths for both processes. Symmetry reducing effects at the surface are responsible for a pronounced asymmetry of the acceptor contrasts along the principal [001] axis. Uniaxial strain fields due to surface relaxation and spin orbit interaction of the tip induced electric field are discussed on the basis of band structure calculations. High-resolution STS studies of acceptor atoms in an operating p-i-n diode confirm that an electric field indeed changes the acceptor contrasts. In conclusion, the anisotropic contrasts of acceptors are created by the host crystal's band structure and concomitant symmetry reduction effects at the surface. (orig.)

  6. Phase-coherent transport and spin-orbit-coupling in III/V-semiconductor nanowires; Phasenkohaerenter Transport und Spin-Bahn-Wechselwirkung in III/V-Halbleiternanodraehten

    Energy Technology Data Exchange (ETDEWEB)

    Estevez Hernandez, Sergio


    Semiconductor nanowires fabricated by a bottom-up approach are not only interesting for the realization of future nanoscaled devices but also appear to be very attractive model systems to tackle fundamental questions concerning the transport in strongly confined systems. In order to avoid the problem connected with carrier depletion, narrowband gap semiconductors, i.e., InAs or InN, or core-shell Nanowires, i.e., GaAs/AlGaAs, are preferred. The underlying reason is that in InAs or InN the Fermi-level pinning in the conduction band results in a carrier accumulation at the surface. In fact, the tubular topology of the surface electron gas opens up the possibility to observe unconventional quantum transport phenomena. When the phase-coherence length in the nanowire is comparable to its dimensions the conductance fluctuates if a magnetic field is applied or if the electron concentration is changed by means of a gate electrode. These so-called universal conductance fluctuations being in the order of e{sup 2}/h originate from the fact that in small disordered samples, electron interference effects are not averaged out. In this work are analyzed universal conductance fluctuations to study the quantum transport properties in InN, InAs and GaAs/AlGaAs nanowires. With the use of a magnetic field and a back-gate electrode the universal conductance fluctuations and localizations effects were analyzed. Since InN and InAs are narrow band gap semiconductors, one naturally expects spin-orbit coupling effects. Because this phenomena is of importance for spin electronic applications. However, owing to the cylindrical symmetry of the InN and InAs nanowires, the latter effect was observable and actually be used to determine the strength of spin-orbit coupling. In order to clearly separate the weak antilocalization effect from the conductance fluctuations, the averaging of the magnetoconductance at different gate voltages was essential. The low-temperature quantum transport properties

  7. Semiconducting III-V compounds

    CERN Document Server

    Hilsum, C; Henisch, Heinz R


    Semiconducting III-V Compounds deals with the properties of III-V compounds as a family of semiconducting crystals and relates these compounds to the monatomic semiconductors silicon and germanium. Emphasis is placed on physical processes that are peculiar to III-V compounds, particularly those that combine boron, aluminum, gallium, and indium with phosphorus, arsenic, and antimony (for example, indium antimonide, indium arsenide, gallium antimonide, and gallium arsenide).Comprised of eight chapters, this book begins with an assessment of the crystal structure and binding of III-V compounds, f

  8. Fast pixelated sensors for radiation detection and imaging based on quantum confined structures in III/V semiconductors (United States)

    Tortora, M.; Biasiol, G.; Cautero, G.; Menk, R. H.; Plaisier, J. R.; Antonelli, M.


    In order to improve the characterisation of the delivered beams in many types of photon sources, innovative beam profilers based on III/V semiconductor materials (InGaAs/InAlAs) have been deeply investigated. Owing to a tunable and direct band gap these devices allow radiation detection in a wide spectral range. In order to increase the sensitivity of the device in radiation detection charge amplification on the sensor level is implemented. This is obtained by exploiting In0.75Ga0.25As/In0.75Al0.25As quantum wells (QW) hosting a two-dimensional electron gas (2DEG) through molecular beam epitaxy (MBE). Internal charge-amplification mechanism can be achieved for very low applied voltages, while the high carrier mobility allows the design of very fast photon detectors with sub-nanosecond response times. This technology has been preliminarily exploited to fabricate prototype beam profilers with a strip geometry (with 50-μm-wide strips). Tests were carried out both with conventional X-ray tubes and at the Elettra synchrotron facility. The results testify how these profilers are capable of reconstructing the shape of the beam, as well as estimating the position of the beam centroid with a precision of about 400 nm. Further measurements with different samples of decreasing thickness have shown how this precision could be further improved by an optimised microfabrication. For this reason a new design, based on a membrane-photodetector, is proposed. Results regarding the spatial resolution as function of the sensor thickness will be presented and discussed.

  9. Comprehension of Postmetallization Annealed MOCVD-TiO2 on (NH42S Treated III-V Semiconductors

    Directory of Open Access Journals (Sweden)

    Ming-Kwei Lee


    Full Text Available The electrical characteristics of TiO2 films grown on III-V semiconductors (e.g., p-type InP and GaAs by metal-organic chemical vapor deposition were studied. With (NH42S treatment, the electrical characteristics of MOS capacitors are improved due to the reduction of native oxides. The electrical characteristics can be further improved by the postmetallization annealing, which causes hydrogen atomic ion to passivate defects and the grain boundary of polycrystalline TiO2 films. For postmetallization annealed TiO2 on (NH42S treated InP MOS, the leakage current densities can reach 2.7 × 10−7 and 2.3 × 10−7 A/cm2 at ±1 MV/cm, respectively. The dielectric constant and effective oxide charges are 46 and 1.96 × 1012 C/cm2, respectively. The interface state density is 7.13×1011 cm−2 eV−1 at the energy of 0.67 eV from the edge of valence band. For postmetallization annealed TiO2 on (NH42S treated GaAs MOS, The leakage current densities can reach 9.7×10−8 and 1.4×10−7 at ±1 MV/cm, respectively. The dielectric constant and effective oxide charges are 66 and 1.86×1012 C/cm2, respectively. The interface state density is 5.96×1011 cm−2 eV−1 at the energy of 0.7 eV from the edge of valence band.

  10. Monitoring of stress relaxation and defect formation in metamorphic III-V semiconductor heterostructures for high-efficiency solar cells; Kontrolle von Spannungsrelaxation und Defektbildung in metamorphen III-V Halbleiterheterostrukturen fuer hocheffiziente Solarzellen

    Energy Technology Data Exchange (ETDEWEB)

    Schoene, Jan


    The paper discusses the further development of monolithic III-V multiple solar cells with three pn transitions for applications in concentrating PV systems. These triple solar cells consist of a GaInP upper cell, a GaInAs middle cell and a germanium lower cell, which are connected via electrically conducting and optically transparent tunnel diodes. Efficiencies are higher than 40 % with concentrated light. Demands on materials for III-V high-efficiency solar cells are extremely high. Especially in the metamorphic triple solar cell, for which compound semiconductors with different interatomic distances are deposited epitactically on each other, crystal defects may occur that impair the performance of the solar cell. The use of appropriate layer growing concepts may manipulate the formation of crystal defects and minimize their influence on solar cell performance. Both conventional and high-resolution transmission electron microscopy (TEM and HRTEM) as well as high-resolution X-ray diffraction (HRXRD) were applied successfully for investigating defect formation and layer stresses. In the investigations described, these methods were applied to develop a high-efficiency triple solar cell with a world first efficiency of 41.1 percent in concentrated light. [German] Diese Arbeit beschaeftigt sich mit der Weiterentwicklung von monolithischen III-V-Mehrfach-Solarzellen mit drei pn-Uebergaengen fuer die Anwendung in konzentrierenden Photovoltaiksystemen. Diese Tripelsolarzellen bestehen aus einer GaInP-Oberzelle, einer GaInAs-Mittelzelle und einer Germanium-Unterzelle, die mittels elektrisch leitender und optisch transparenter Tunneldioden verbunden sind. Derartige Solarzellen erzielen mittlerweile Rekordwirkungsgrade von mehr als 40 % unter konzentriertem Licht. Bei den III-V Hocheffizienzsolarzellen sind die Anforderungen an die Materialqualitaet ausserordentlich hoch. Insbesondere bei der metamorphen Tripelsolarzelle, bei der Verbindungshalbleiter mit unterschiedlichen

  11. Position-controlled III-V compound semiconductor nanowire solar cells by selective-area metal-organic vapor phase epitaxy. (United States)

    Fukui, Takashi; Yoshimura, Masatoshi; Nakai, Eiji; Tomioka, Katsuhiro


    We demonstrate position-controlled III-V semiconductor nanowires (NWs) by using selective-area metal-organic vapor phase epitaxy and their application to solar cells. Efficiency of 4.23% is achieved for InP core-shell NW solar cells. We form a 'flexible NW array' without a substrate, which has the advantage of saving natural resources over conventional thin film photovoltaic devices. Four junction NW solar cells with over 50% efficiency are proposed and discussed.

  12. A Review of Ultrahigh Efficiency III-V Semiconductor Compound Solar Cells: Multijunction Tandem, Lower Dimensional, Photonic Up/Down Conversion and Plasmonic Nanometallic Structures

    Directory of Open Access Journals (Sweden)

    Katsuaki Tanabe


    Full Text Available Solar cells are a promising renewable, carbon-free electric energy resource to address the fossil fuel shortage and global warming. Energy conversion efficiencies around 40% have been recently achieved in laboratories using III-V semiconductor compounds as photovoltaic materials. This article reviews the efforts and accomplishments made for higher efficiency III-V semiconductor compound solar cells, specifically with multijunction tandem, lower-dimensional, photonic up/down conversion, and plasmonic metallic structures. Technological strategies for further performance improvement from the most efficient (AlInGaP/(InGaAs/Ge triple-junction cells including the search for 1.0 eV bandgap semiconductors are discussed. Lower-dimensional systems such as quantum well and dot structures are being intensively studied to realize multiple exciton generation and multiple photon absorption to break the conventional efficiency limit. Implementation of plasmonic metallic nanostructures manipulating photonic energy flow directions to enhance sunlight absorption in thin photovoltaic semiconductor materials is also emerging.

  13. Semiconductors. Subvol. A. New data and updates for I-VII, III-V, III-VI and IV-VI compounds

    Energy Technology Data Exchange (ETDEWEB)

    Roessler, U (ed.) [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Dietl, T.; Dobrowolski, W.; Story, T. [Polish Academy of Sciences, Warszawa (Poland). Lab. for Cryogenic and Spintronic Research; Fernandes da Silva, E.C. [Universidade de Sao Paulo, SP (Brazil). Lab. de Novos Materiais Semiconductores; Hoenerlage, B. [IPCMS/GONLO, 67 - Strasbourg (France); Meyer, B.K. [Giessen Univ. (Germany). 1. Physikalisches Inst.


    The Landolt-Boernstein subvolumes III/44A and III/44B update the existing 8 volumes III/41 about Semiconductors and contain new Data and Updates for I-VII, III-V, III-VI, IV, VI and II-VI Compounds. The text, tables figures and references are provided in self-contained document files, each one dedicated to a substance and property. The first subvolume III/44A contains a ''Systematics of Semiconductor Properties'', which should help the non-specialist user to understand the meaning of the material parameters. Hyperlinked lists of substances and properties lead directly to the documents and make the electronic version an easy-to-use source of semiconductor data. In the new updates III/44A and III/44B, links to existing material in III/41 or to related documents for a specific substance are also included. (orig.)

  14. Molecular beam epitaxy engineered III-V semiconductor structures for low-power optically addressed spatial light modulators (United States)

    Larsson, Anders G.; Maserjian, Joseph


    Device approaches are investigated for optically addressed SLMs based on molecular-beam epitaxy (MBE) engineered III-V materials and structures. Strong photooptic effects can be achieved in periodically delta-doped multiple-quantum-well structures, but are still insufficient for high-contrast modulation with only single- or double-pass absorption through active layers of practical thickness. The asymmetric Fabry-Perot cavity approach is employed to permit extinction of light due to interference of light reflected from the front and back surfaces of the cavity. This approach is realized with an all-MBE-grown structure consisting of GaAs/AlAs quarter-wave stack reflector grown over the GaAs substrate as the high reflectance mirror and the GaAs surface as the low reflectance mirror. High-contrast modulation is achieved using a low-power InGaAs/GaAs quantum well laser for the control signal.

  15. Large Magnetic Moments of Arsenic-Doped Mn Clusters and their Relevance to Mn-Doped III-V Semiconductor Ferromagnetism

    CERN Document Server

    Kabir, M; Mookerjee, A; Kabir, Mukul; Mookerjee, Abhijit


    We report electronic and magnetic structure of arsenic-doped manganese clusters from density-functional theory using generalized gradient approximation for the exchange-correlation energy. We find that arsenic stabilizes manganese clusters, though the ferromagnetic coupling between Mn atoms are found only in Mn$_2$As and Mn$_4$As clusters with magnetic moments 9 $\\mu_B$ and 17 $\\mu_B$, respectively. For all other sizes, $x=$ 3, 5-10, Mn$_x$As clusters show ferrimagnetic coupling. It is suggested that, if grown during the low temperature MBE, the giant magnetic moments due to ferromagnetic coupling in Mn$_2$As and Mn$_4$As clusters could play a role on the ferromagnetism and on the variation observed in the Curie temperature of Mn-doped III-V semiconductors.

  16. Large-signal characterizations of DDR IMPATT devices based on group III-V semiconductors at millimeter-wave and terahertz frequencies (United States)

    Acharyya, Aritra; Mallik, Aliva; Banerjee, Debopriya; Ganguli, Suman; Das, Arindam; Dasgupta, Sudeepto; Banerjee, J. P.


    Large-signal (L-S) characterizations of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on group III-V semiconductors such as wurtzite (Wz) GaN, GaAs and InP have been carried out at both millimeter-wave (mm-wave) and terahertz (THz) frequency bands. A L-S simulation technique based on a non-sinusoidal voltage excitation (NSVE) model developed by the authors has been used to obtain the high frequency properties of the above mentioned devices. The effect of band-to-band tunneling on the L-S properties of the device at different mm-wave and THz frequencies are also investigated. Similar studies are also carried out for DDR IMPATTs based on the most popular semiconductor material, i.e. Si, for the sake of comparison. A comparative study of the devices based on conventional semiconductor materials (i.e. GaAs, InP and Si) with those based on Wz-GaN shows significantly better performance capabilities of the latter at both mm-wave and THz frequencies.

  17. Density Functional Theory Simulations of Semiconductors for Photovoltaic Applications: Hybrid Organic-Inorganic Perovskites and III/V Heterostructures

    Directory of Open Access Journals (Sweden)

    Jacky Even


    Full Text Available Potentialities of density functional theory (DFT based methodologies are explored for photovoltaic materials through the modeling of the structural and optoelectronic properties of semiconductor hybrid organic-inorganic perovskites and GaAs/GaP heterostructures. They show how the properties of these bulk materials, as well as atomistic relaxations, interfaces, and electronic band-lineups in small heterostructures, can be thoroughly investigated. Some limitations of available standard DFT codes are discussed. Recent improvements able to treat many-body effects or based on density-functional perturbation theory are also reviewed in the context of issues relevant to photovoltaic technologies.

  18. Systematic defect donor levels in III-V and II-VI semiconductors revealed by hybrid functional density-functional theory (United States)

    Petretto, Guido; Bruneval, Fabien


    The identification of defect levels from photoluminescence spectroscopy is a useful but challenging task. Density-functional theory (DFT) is a highly valuable tool to this aim. However, the semilocal approximations of DFT that are affected by a band gap underestimation are not reliable to evaluate defect properties, such as charge transition levels. It is now established that hybrid functional approximations to DFT improve the defect description in semiconductors. Here we demonstrate that the use of hybrid functionals systematically stabilizes donor defect states in the lower part of the band gap for many defects, impurities or vacancies, in III-V and in II-VI semiconductors, even though these defects are usually considered as acceptors. These donor defect states are a very general feature and, to the best of our knowledge, have been overlooked in previous studies. The states we identify here may challenge the older assignments to photoluminescent peaks. Though appealing to screen quickly through the possible stable charge states of a defect, semilocal approximations should not be trusted for that purpose.

  19. Transformational III-V Electronics

    KAUST Repository

    Nour, Maha A.


    Flexible electronics using III-V materials for nano-electronics with high electron mobility and optoelectronics with direct band gap are attractive for many applications. This thesis describes a complementary metal oxide semiconductor (CMOS) compatible process for transforming traditional III-V materials based electronics into flexible one. The thesis reports releasing 200 nm of Gallium Arsenide (GaAs) from 200 nm GaAs / 300 nm Aluminum Arsenide (AlAs) stack on GaAs substrate using diluted hydrofluoric acid (HF). This process enables releasing a single top layer compared to peeling off all layers with small sizes at the same time. This is done utilizing a network of release holes that contributes to the better transparency (45 % at 724 nm wavelengths) observed. Fabrication of metal oxide semiconductor capacitor (MOSCAPs) on GaAs is followed by releasing it to have devices on flexible 200 nm GaAs. Similarly, flexible GaSb and InP fabrication process is also reported to transform traditional electronics into large-area flexible electronics.

  20. Luminescence of Lanthanides and Actinides Implanted into Binary III-V semiconductors and AlGaAs (United States)


    16th International Symposium on Gallium Arsenide and Related Compounds, 25-29 Sep1 1989, 1ruiz~a, agano, Japan. Refereed paper to appear in ~Uyr...valve on the cryostat and using a Lakeshore Cryogenics Model DRC - 80C digital temperature contoller with a calibrated GaAs diode and three 3 W heaters

  1. Hybrid III-V/silicon lasers (United States)

    Kaspar, P.; Jany, C.; Le Liepvre, A.; Accard, A.; Lamponi, M.; Make, D.; Levaufre, G.; Girard, N.; Lelarge, F.; Shen, A.; Charbonnier, P.; Mallecot, F.; Duan, G.-H.; Gentner, J.-.; Fedeli, J.-M.; Olivier, S.; Descos, A.; Ben Bakir, B.; Messaoudene, S.; Bordel, D.; Malhouitre, S.; Kopp, C.; Menezo, S.


    The lack of potent integrated light emitters is one of the bottlenecks that have so far hindered the silicon photonics platform from revolutionizing the communication market. Photonic circuits with integrated light sources have the potential to address a wide range of applications from short-distance data communication to long-haul optical transmission. Notably, the integration of lasers would allow saving large assembly costs and reduce the footprint of optoelectronic products by combining photonic and microelectronic functionalities on a single chip. Since silicon and germanium-based sources are still in their infancy, hybrid approaches using III-V semiconductor materials are currently pursued by several research laboratories in academia as well as in industry. In this paper we review recent developments of hybrid III-V/silicon lasers and discuss the advantages and drawbacks of several integration schemes. The integration approach followed in our laboratory makes use of wafer-bonded III-V material on structured silicon-on-insulator substrates and is based on adiabatic mode transfers between silicon and III-V waveguides. We will highlight some of the most interesting results from devices such as wavelength-tunable lasers and AWG lasers. The good performance demonstrates that an efficient mode transfer can be achieved between III-V and silicon waveguides and encourages further research efforts in this direction.

  2. A comprehensive study of the magnetic, structural, and transport properties of the III-V ferromagnetic semiconductor InMnP

    Energy Technology Data Exchange (ETDEWEB)

    Khalid, M.; Hübner, R.; Baehtz, C.; Skorupa, W.; Zhou, Shengqiang, E-mail: [Helmholtz-Zentrum Dresden Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, D-01328 Dresden (Germany); Gao, Kun; Helm, M. [Helmholtz-Zentrum Dresden Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, D-01328 Dresden (Germany); Technische Universität Dresden, 01062 Dresden (Germany); Weschke, E. [Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen-Campus BESSY II, D-12489 Berlin (Germany); Gordan, O.; Salvan, G.; Zahn, D. R. T. [Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz (Germany)


    The manganese induced magnetic, electrical, and structural modification in InMnP epilayers, prepared by Mn ion implantation and pulsed laser annealing, are investigated in the following work. All samples exhibit clear hysteresis loops and strong spin polarization at the Fermi level. The degree of magnetization, the Curie temperature, and the spin polarization depend on the Mn concentration. The bright-field transmission electron micrographs show that InP samples become almost amorphous after Mn implantation but recrystallize after pulsed laser annealing. We did not observe an insulator-metal transition in InMnP up to a Mn concentration of 5 at. %. Instead all InMnP samples show insulating characteristics up to the lowest measured temperature. Magnetoresistance results obtained at low temperatures support the hopping conduction mechanism in InMnP. We find that the Mn impurity band remains detached from the valence band in InMnP up to 5 at. % Mn doping. Our findings indicate that the local environment of Mn ions in InP is similar to GaMnAs, GaMnP, and InMnAs; however, the electrical properties of these Mn implanted III-V compounds are different. This is one of the consequences of the different Mn binding energy in these compounds.

  3. Thermal expansion coefficient of binary semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, V.; Sastry, B.S.R. [Indian School of Mines, Dhanbad (India). Dept. of Electronics and Instrumentation


    The linear thermal expansion coefficient of tetrahedrally coordinated A{sup II}B{sup VI} and A{sup III}B{sup V} semiconductors has been calculated using plasmon energy data. A simple relation between the bond length and plasmon energy has been derived. The calculated values of thermal expansion coefficient and bond length have been compared with the experimental values and the values reported by different workers. An excellent experiment has been obtained between them. (orig.)

  4. III-V compound SC for optoelectronic devices

    Directory of Open Access Journals (Sweden)

    Sudha Mokkapati


    Full Text Available III-V compound semiconductors (SC have played a crucial role in the development of optoelectronic devices for a broad range of applications. Major applications of InP or GaAs based III-V compound SC are devices for optical fiber communications, infrared and visible LEDs/LDs and high efficiency solar cells. GaN based compounds are extremely important for short wavelength light emitters used in solid state lighting systems. We review the important device applications of various III-V compound SC materials.

  5. Optical properties of InAsBi and optimal designs of lattice-matched and strain-balanced III-V semiconductor superlattices (United States)

    Webster, P. T.; Shalindar, A. J.; Riordan, N. A.; Gogineni, C.; Liang, H.; Sharma, A. R.; Johnson, S. R.


    The optical properties of bulk InAs0.936Bi0.064 grown by molecular beam epitaxy on a (100)-oriented GaSb substrate are measured using spectroscopic ellipsometry. The index of refraction and absorption coefficient are measured over photon energies ranging from 44 meV to 4.4 eV and are used to identify the room temperature bandgap energy of bulk InAs0.936Bi0.064 as 60.6 meV. The bandgap of InAsBi is expressed as a function of Bi mole fraction using the band anticrossing model and a characteristic coupling strength of 1.529 eV between the Bi impurity state and the InAs valence band. These results are programmed into a software tool that calculates the miniband structure of semiconductor superlattices and identifies optimal designs in terms of maximizing the electron-hole wavefunction overlap as a function of transition energy. These functionalities are demonstrated by mapping the design spaces of lattice-matched GaSb/InAs0.911Sb0.089 and GaSb/InAs0.932Bi0.068 and strain-balanced InAs/InAsSb, InAs/GaInSb, and InAs/InAsBi superlattices on GaSb. The absorption properties of each of these material systems are directly compared by relating the wavefunction overlap square to the absorption coefficient of each optimized design. Optimal design criteria are provided for key detector wavelengths for each superlattice system. The optimal design mid-wave infrared InAs/InAsSb superlattice is grown using molecular beam epitaxy, and its optical properties are evaluated using spectroscopic ellipsometry and photoluminescence spectroscopy.

  6. Practical routes to (SiH₃)₃P: applications in group IV semiconductor activation and in group III-V molecular synthesis. (United States)

    Tice, Jesse B; Chizmeshya, A V G; Tolle, J; D' Costa, V R; Menendez, J; Kouvetakis, J


    The (SiH₃)₃P hydride is introduced as a practical source for n-doping of group IV semiconductors and as a highly-reactive delivery agent of -(SiH₃)₂P functionalities in exploratory synthesis. In contrast to earlier methods, the compound is produced here in high purity quantitative yields via a new single-step method based on reactions of SiH₃Br and (Me₃Sn)₃P, circumventing the need for toxic and unstable starting materials. As an initial demonstration of its utility we synthesized monosubstituted Me₂M-P(SiH₃)₂ (M = Al, Ga, In) derivatives of Me₃M containing the (SiH₃)₂P ligand for the first time, in analogy to the known Me₂M-P(SiMe₃)₂ counterparts. A dimeric structure of Me₂M-P(SiH₃)₂ is proposed on the basis of spectroscopic characterizations and quantum chemical simulations. Next, in the context of materials synthesis, the (SiH₃)₃P compound was used to dope germanium for the first time by building a prototype p(++)Si(100)/i-Ge/n-Ge photodiode structure. The resultant n-type Ge layers contained active carrier concentrations of 3-4 × 10¹⁹ atoms cm⁻³ as determined by spectroscopic ellipsometry and confirmed by SIMS. Strain analysis using high resolution XRD yielded a Si content of 4 × 10²⁰ atoms cm⁻³ in agreement with SIMS and within the range expected for incorporating Si₃P type units into the diamond cubic Ge matrix. Extensive characterizations for structure, morphology and crystallinity indicate that the Si co-dopant plays essentially a passive role and does not compromise the device quality of the host material nor does it fundamentally alter its optical properties.

  7. Electronic Properties of III-V Semiconductors under [111] Uniaxial Strain; a Tight-Binding Approach: I. Arsenides and Gallium Phosphide

    Directory of Open Access Journals (Sweden)

    Miguel E. Mora-Ramos


    Full Text Available Empleando un esquema de cálculo tight-binding que usa una base de orbitales sp3s*d5, se estudian propiedades de la estructura electrónica de un grupo de materiales semiconductores IIIV los cuales son de notable interés para la tecnología de dispositivos electrónicos y optoelectrónicos. En específico, se analiza la influencia sobre estas propiedades de una tensión aplicada según la dirección cristalográfica [111], haciendo uso de una formulación basada en la teoría de la elasticidad para establecer las posiciones relativas de los iones vecinos más próximos. Especial atención se presta a la inclusión del efecto de deformación interna de la red cristalina. Para cada material de los estudiados presentamos las dependencias de las brechas energéticas asociadas a los puntos L, X y L de la zona de Brillouin como funciones de la tensión uniaxial en AlAs, GaAs, InAs y GaP. Asimismo, reportamos expresiones de ajuste para los valores de las masas efectivas de conducción en esos cuatro materiales. La comparación de la variación de la brecha de energía en X para el GaP, calculada con nuestro modelo, y recientes resultados experimentales para la transición indirecta entre la banda de huecos pesados y la banda X de conducción arroja una muy buena concordancia.

  8. Structural and Thermal Properties of Elementary and Binary Tetrahedral Semiconductor Nanoparticles (United States)

    Omar, M. S.


    We report an equation free from fitting parameters as a direct calculation of size-dependent mean bond length for group IV and compounds from the III-V and II-VI binary groups. Size-dependent melting temperature and thermal expansion are also investigated for some materials forming the groups mentioned above. The empirical relation, which is obtained from fitting experimental data of melting enthalpy, is used to recalculate their values as well as entropy. The nanosize dependence of lattice thermal expansion for elements forming group IV is analyzed according to the hard sphere model, while mean ionicity is used for groups III-V and II-VI.

  9. Studies on II-VI and III-V semiconductor nanostructures. Introduction of the core/shell/shell structure and development of CdSe nanocrystals in an automatized procedure; Untersuchungen an II-VI und III-V Halbleiternanostrukturen. Einfuehrung der Core/shell/shell-Struktur und Darstellung von CdSe-Nanokristallen in einem automatisierten Verfahren

    Energy Technology Data Exchange (ETDEWEB)

    Mekis, I.


    The work in this dissertation is focused on the development and characterization of fluorescent II-VI and III-V-Nanomaterials. Highly luminescent and photostable Nanocrystals with narrow size distributions were prepared. It was shown that nearly monodisperse CdSe-Nanocrystals could be prepared from Cd(Ac){sub 2} and TOPSe in a mixture of TOPO/TOP/HDA/TDPA. Nearly monodisperse CdSe/CdS-Core/shell-Nanocrystals have been prepared in a one-pot-synthesis by injection of H{sub 2}S-Gas into a freshly prepared crude solution of CdSe. The passivation of the CdSe-core with an inorganic shell of CdS resulted in the drastic improvement of the photoluminescence-efficiency of the colloidal solution. Reproducible room-temperature quantum yields reached up to a value of 85%. Photostability investigations have proved the enhanced stability of CdSe/CdS-Nanocrystals compared to CdSe-Nanocrystals under illumination with UV-Light. A novel type of luminescent semiconductor nanocrystal structure has been developed, consisting of a CdSe core and two anorganic shells. Highly fluorescent and nearly monodisperse CdSe/CdS/ZnS- and CdSe/ZnSe/ZnS-Core/shell/shell-nanocrystals have been prepared via organometallic- and acetate-precursors. The Core/she ll/shell particles reached reproducible room-temperature quantum yields up to 85%. Photostability investigations among CdSe-core, CdSe/CdS-Core/shell- and CdSe/CdS/ZnS- Core/shell/-shell-nanocrystals under illumination with UV-light have proved the highest photostability of the Core/shell/shell-particles. The photostabilities of CdSe/ZnSe/ZnS-and CdSe/ZnS-nanocrystals were compared under illumination with intense laser-beam in air. Another part of this work focused on the development of an automated synthesis procedure of CdSe-nanocrystals by constructing and implementing a flow-reactor system. The size and structure of prepared nanocrystals depended considerably on the Cd:Se-precursorratio and the flow-rate. The preparation of CdSe using Cd(Ac)2

  10. Analysis and evaluation for practical application of photovoltaic power generation system. Analysis and evaluation for development of extra-high efficiency solar cells (fundamental research on extra-high efficiency III-V compound semiconductor tandem solar cells); Taiyoko hatsuden system jitsuyoka no tame no kaiseki hyoka. Chokokoritsu taiyo denchi no gijutsu kaihatsu no tame no kaiseki hyoka (chokokoritsu III-V zoku kagobutsu taiyo denchi gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    Sekikawa, T.; Kawanami, H.; Sakata, I.; Nagai, K.; Matsumoto, K.; Miki, K. [Electrotechnical Laboratory, Tsukuba (Japan)


    Described herein are the results of the FY1994 research program for development of extra-high efficiency III-V compound semiconductor tandem solar cells. Heteroepitaxial structures of compound semiconductors, such as GaAs, on silicon substrates are analyzed and evaluated by EXAFS, Raman and RHEED for the initial stage of the film growth and heterointerfaces. The device capable of in-situ observation of the growing surface structures during the period of heteroepitaxial film growth is introduced, to investigate the effects of rise-up and initial growth conditions on defects. The effects of atomic hydrogen on growth of a GaAs film on a silicon substrate are investigated from photoluminescence and solar cell characteristics, to confirm the effects of reducing defects. Heteroepitaxial growth of InGaP, which has the optimum band width for forming multi-junction silicon solar cells, on a silicon substrate is investigated, to find that an interfacial buffer layer is necessary to form a good film. 2 figs.

  11. Integration of III-V materials and Si-CMOS through double layer transfer process (United States)

    Lee, Kwang Hong; Bao, Shuyu; Fitzgerald, Eugene; Tan, Chuan Seng


    A method to integrate III-V compound semiconductor and SOI-CMOS on a common Si substrate is demonstrated. The SOI-CMOS layer is temporarily bonded on a Si handle wafer. Another III-V/Si substrate is then bonded to the SOI-CMOS containing handle wafer. Finally, the handle wafer is released to realize the SOI-CMOS on III-V/Si hybrid structure on a common substrate. Through this method, high temperature III-V materials growth can be completed without the presence of the temperature sensitive CMOS layer, hence damage to the CMOS layer is avoided.

  12. Discontinuities and bands alignments of strain-balanced III-V-N/III-V-Bi heterojunctions for mid-infrared photodetectors (United States)

    Chakir, K.; Bilel, C.; Habchi, M. M.; Rebey, A.


    We have developed a 10- and 14-band anticrossing (BAC) models to investigate the band structures of dilute nitrides and dilute bismides alloys. In fact, the addition of Bi or N to III-V semiconductors causes a significant reduction in the band gap energy and an enhancement of the spin-orbit splitting energy. Further, the conduction and valence offsets between III-V-N/III-V-Bi were also investigated for different nitrogen and bismuth concentrations. For III-V-N/III-V-Bi heterojunctions, the strain-balanced criteria were undertaken by the zero stress analysis. The band alignment of strain-balanced GaAsN/GaAsBi, InPN/InPBi and InAsN/InAsBi is a type II. For InSbN/InSbBi heterostructure, the band lineup can be type I or II.

  13. Subnanometer scale characterization of III-V-heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Lakner, H. [Gerhard-Mercator-Univ. Duisburg (Germany). Werkstoffe der Elektrotechnik


    Heterostructures based on III-V semiconductors play a dominant role for the production of optoelectronic /1/ and electronic high-speed or high-frequency /2/ devices. The necessary band-gap engineering is achieved by optimized growth procedures which allow to change the chemical composition and the crystal structure (e.g., strain or ordering) on the subnanometer scale. The evaluation of individual heterointerfaces with respect to chemical composition and crystal structure requires characterization techniques which offer the necessary high spatial resolution. Scanning transmission electron microscopy (STEM) offers several of such quantitative techniques. It is the intention of this paper to demonstrate the capabilities of STEM in the subnanometer characterization of III-V-heterostructures based on InP-substrates. Additionally, the data obtained from nanocharacterization can be correlated to device performance.

  14. Physics, fabrication and characterization of III-V multi-gate FETs for low power electronics (United States)

    Thathachary, Arun V.

    With transistor technology close to its limits for power constrained scaling and the simultaneous emergence of mobile devices as the dominant driver for new scaling, a pathway to significant reduction in transistor operating voltage to 0.5V or lower is urgently sought. This however implies a fundamental paradigm shift away from mature Silicon technology. III-V compound semiconductors hold great promise in this regard due to their vastly superior electron transport properties making them prime candidates to replace Silicon in the n-channel transistor. Among the plethora of binary and ternary compounds available in the III-V space, InxGa1-xAs alloys have attracted significant interest due to their excellent electron mobility, ideally placed bandgap and mature growth technology. Simultaneously, electrostatic control mandates multigate transistor designs such as the FinFET at extremely scaled nodes. This dissertation describes the experimental realization of III-V FinFETs incorporating InXGa1-XAs heterostructure channels for high performance, low power logic applications. The chapters that follow present experimental demonstrations, simulations and analysis on the following aspects (a) motivation and key figures of merit driving material selection and design; (b) dielectric integration schemes for high-k metal-gate stack (HKMG) realization on InXGa 1-XAs, including surface clean and passivation techniques developed for high quality interfaces; (c) novel techniques for transport (mobility) characterization in nanoscale multi-gate FET architectures with experimental demonstration on In0.7Ga0.3As nanowires; (d) Indium composition and quantum confined channel design for InXGa 1-XAs FinFETs and (e) InAs heterostructure designs for high performance FinFETs. Each chapter also contains detailed benchmarking of results against state of the art demonstrations in Silicon and III-V material systems. The dissertation concludes by assessing the feasibility of InXGa 1-XAs Fin

  15. Antimony Based III-V Thermophotovoltaic Devices

    Energy Technology Data Exchange (ETDEWEB)

    CA Wang


    Antimony-based III-V thermophotovoltaic (TPV) cells are attractive converters for systems with low radiator temperature around 1100 to 1700 K, since these cells potentially can be spectrally matched to the thermal source. Cells under development include GaSb and the lattice-matched GaInAsSb/GaSb and InPAsSb/InAs quaternary systems. GaSb cell technology is the most mature, owing in part to the relative ease in preparation of the binary alloy compared to quaternary GaInAsSb and InPAsSb alloys. Device performance of 0.7-eV GaSb cells exceeds 90% of the practical limit. GaInAsSb TPV cells have been the primary focus of recent research, and cells with energy gap E{sub g} ranging from {approx}0.6 to 0.49 eV have been demonstrated. Quantum efficiency and fill factor approach theoretical limits. Open-circuit voltage factor is as high as 87% of the practical limit for the higher-E{sub g} cells, but degrades to below 80% with decreasing E{sub g} of the alloy, which might be due to Auger recombination. InPAsSb cells are the least studied, and a cell with E{sub g} = 0.45-eV has extended spectral response out to 4.3 {micro}m. This paper briefly reviews the main contributions that have been made for antimonide-based TPV cells, and suggests additional studies for further performance enhancements.

  16. Ultra-high-throughput Production of III-V/Si Wafer for Electronic and Photonic Applications. (United States)

    Geum, Dae-Myeong; Park, Min-Su; Lim, Ju Young; Yang, Hyun-Duk; Song, Jin Dong; Kim, Chang Zoo; Yoon, Euijoon; Kim, SangHyeon; Choi, Won Jun


    Si-based integrated circuits have been intensively developed over the past several decades through ultimate device scaling. However, the Si technology has reached the physical limitations of the scaling. These limitations have fuelled the search for alternative active materials (for transistors) and the introduction of optical interconnects (called "Si photonics"). A series of attempts to circumvent the Si technology limits are based on the use of III-V compound semiconductor due to their superior benefits, such as high electron mobility and direct bandgap. To use their physical properties on a Si platform, the formation of high-quality III-V films on the Si (III-V/Si) is the basic technology ; however, implementing this technology using a high-throughput process is not easy. Here, we report new concepts for an ultra-high-throughput heterogeneous integration of high-quality III-V films on the Si using the wafer bonding and epitaxial lift off (ELO) technique. We describe the ultra-fast ELO and also the re-use of the III-V donor wafer after III-V/Si formation. These approaches provide an ultra-high-throughput fabrication of III-V/Si substrates with a high-quality film, which leads to a dramatic cost reduction. As proof-of-concept devices, this paper demonstrates GaAs-based high electron mobility transistors (HEMTs), solar cells, and hetero-junction phototransistors on Si substrates.

  17. Semiconductor lasers and herterojunction leds

    CERN Document Server

    Kressel, Henry


    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

  18. Quantum transport in III-V-semiconductor nanocolumns; Quantentransport in III-V-Halbleiternanosaeulen

    Energy Technology Data Exchange (ETDEWEB)

    Wensorra, Jakob


    The goal of this work has been to investigate und understand the electronic transport properties of vertical GaAs/AlAs nanocolumn resonant tunneling diodes (RTDs) and field effect transistors (RTTs) as well as of vertical InAs nanocolumn phase interference diodes. Besides the fabrication and electrical characterization of the devices, numerical calculations, simulations and quantum transport models represent the second important part of the work. GaAs/AlAs and InAs nanocolumns with lateral dimensions down to 30 nm have been processed by top-down approach. Room temperature DC electrical measurements on the nano-RTDs show a distinct negative differential resistance in the I-V characteristics for devices down to 30 nm lateral dimension. The miniaturization of the RTDs leads to the degradation of the transport properties, especially of the peak to valley current ratio (PVR), due to the increased surface scattering. Apart from the main current peak, new substructures can be observed in the I-V characteristics. These are shoulder like features for columns with diameters between 80 nm and 100 nm but become clear peaks when the column diameters are in the 55-75 nm range. For sub-65 nm column lateral dimensions, a strong increase of the PVR and a sharp single peak is observed. A local maximum of the PVR of 3 is reached for columns with 50 nm diameter. The sub-40 nm devices show only space charge limited currents in the I-V characteristics. This behavior can be shifted to smaller or larger diameters by increasing or reduction of the channel doping. For the smallest nanocolumns the lateral quantum confinement, caused by the low dimensionality of the system, leads to the formation of a 3D quantum-point-contact (QPC) in front of the DBQW structure. The quantization in this QPC depends on the column diameter and for a 50 nm column it exceeds the room temperature thermal broadening of the Fermi distribution function of about 25 meV. The measurements of the nano-RTTs indicate a good control of the device current by the gate voltage, without gate leakage. The peak current swing factor (the ratio between peak currents corresponding to the limits of a certain interval of the gate voltage) is about 3 for 150 nm diameter nano-RTTs but reach 6 for 60 nm diameter nano-RTTs (functionality based on the quantum collimation effect). Apart from GaAs/AlAs nanocolumns, InAs nanocolumns have been investigated as well. Nano-diodes were characterized by DC room temperature measurements and low temperature magneto-transport measurements. At room temperature, a linear behavior is observed in the I-V characteristics. Periodic oscillations of the resistance were measured by varying magnetic field at low temperatures. (orig.)

  19. Ⅲ-V族三元化合物半导体材料分子束外延的生长热力学%Thermodynamic analysis of growth of ternary III-V semiconductor materials by molecular-beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    叶志成; 舒永春; 曹雪; 龚亮; 皮彪; 姚江宏; 邢晓东; 许京军


    Thermodynamic models for molecular-beam epitaxy (MBE) growth of ternary Ⅲ-V semiconductor materials are proposed. These models are in agreement with our experimental materials InGaP/GaAs and InGaAs/InP, and reported GaAsP/GaAs and InAsP/InP in thermodynamic growth. The lattice strain energy ΔG and thermal decomposition sensitive to growth temperature are demonstrated in the models simultaneously. ΔG is the function of the alloy composition, which is affected by flux ratio and growth temperature directly. The calculation results reveal that flux ratio and growth temperature mainly influence the growth process. Thermodynamic model of quaternary InGaAsP/GaAs semiconductor material is discussed also.%建立Ⅲ-V族三元化合物半导体材料的分子束外延生长热力学模型.该模型与实验材料InGaP/GaAs, InGaAs/InP 及已发表的GaAsP/GaAs, InAsP/InP 的数据吻合得很好.将晶格应变能ΔG及脱附对温度敏感这两个因素同时纳入热力学模型中,束流和生长温度直接影响合金组分,晶格应变能是合金组分的函数.热力学模型计算结果反映了束流和生长温度是生长过程中最主要的影响因素.讨论和分析了四元半导体材料InGaAsP/GaAs的热力学生长模型.

  20. Fabrication of LEDs based on III-V nitrides and their applications

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, N. [Optoelectronics Technical Division, Toyoda Gosei Co., Ltd., 710 Origuchi, Shimomiyake heiwa-cho, Nakashima-gun, Aichi 490-1312 (Japan)


    III-V nitride semiconductors are useful for LEDs with colors ranging from ultraviolet, blue to green. The luminescence of these LEDs shows a high luminosity and a high purity of color, and, therefore, many applications have been realized using these LEDs. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  1. Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke


    Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

  2. Sulfur passivation techniques for III-V wafer bonding (United States)

    Jackson, Michael James

    The use of direct wafer bonding in a multijunction III-V solar cell structure requires the formation of a low resistance bonded interface with minimal thermal treatment. A wafer bonded interface behaves as two independent surfaces in close proximity, hence a major source of resistance is Fermi level pinning common in III-V surfaces. This study demonstrates the use of sulfur passivation in III-V wafer bonding to reduce the energy barrier at the interface. Two different sulfur passivation processes are addressed. A dry sulfur passivation method that utilizes elemental sulfur vapor activated by ultraviolet light in vacuum is compared with aqueous sulfide and native oxide etch treatments. Through the addition of a sulfur desorption step in vacuum, the UV-S treatment achieves bondable surfaces free of particles contamination or surface roughening. X-ray photoelectron spectroscopy measurements of the sulfur treated GaAs surfaces find lower levels of oxide and the appearance of sulfide species. After 4 hrs of air exposure, the UV-S treated GaAs actually showed an increase in the amount of sulfide bonded to the semiconductor, resulting in less oxidation compared to the aqueous sulfide treatment. Large area bonding is achieved for sulfur treated GaAs / GaAs and InP / InP with bulk fracture strength achieved after annealing at 400 °C and 300 °C respectively, without large compressive forces. The electrical conductivity across a sulfur treated 400 °C bonded n-GaAs/n-GaAs interface significantly increased with a short anneal (1-2 minutes) at elevated temperatures (50--600 °C). Interfaces treated with the NH4OH oxide etch, on the other hand, exhibited only mild improvement in accordance with previously published studies in this area. TEM and STEM images revealed similar interfacial microstructure changes with annealing for both sulfur treated and NH4OH interfaces, whereby some areas have direct semiconductor-semiconductor contact without any interfacial layer. Fitting the

  3. Integration, gap formation, and sharpening of III-V heterostructure nanowires by selective etching

    DEFF Research Database (Denmark)

    Kallesoe, C.; Mølhave, Kristian; Larsen, K. F.;


    Epitaxial growth of heterostructure nanowires allows for the definition of narrow sections with specific semiconductor composition. The authors demonstrate how postgrowth engineering of III-V heterostructure nanowires using selective etching can form gaps, sharpening of tips, and thin sections...... lithography is used for deposition of catalyst particles on trench sidewalls and the lateral growth of III-V nanowires is achieved from such catalysts. The selectivity of a bromine-based etch on gallium arsenide segments in gallium phosphide nanowires is examined, using a hydrochloride etch to remove the III...

  4. Fast optical in situ spectroscopy in III-V MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Kaspari, C.


    This work describes the application of optical in situ measurement techniques (reflectance anisotropy spectroscopy, RAS, and spectroscopic ellipsometry, SE) to processes that are important for the growth of III-V semiconductors like GaAs, InP, InAs and GaP in metal-organic vapour phase epitaxy (MOVPE). Special emphasis is placed on the determination of the free carrier concentration (doping level) and the study of the thermal desorption properties of III-V oxides. A large part of this work is concerned with the development and the construction of a multichannel RAS setup that allows the recording of RAS spectra within fractions of a second. On the basis of benchmark measurements it was shown that the spectral resolution is sufficiently accurate for application in epitaxy. To demonstrate the recording of spectra with high temporal resolution, RAS monolayer oscillations during growth of GaAs were studied and it was shown that the surface changes periodically between a relatively smooth morphology with adsorbed methyl groups (type III) and a stepped, gallium-rich surface (type II). Furthermore the non-reversible process of growing InAs quantum dots on GaAs was studied. It was shown that the multichannel RAS is capable of detecting the 2D-3D transition as well as the following morphological change of the surface at high temporal resolution. For the measurement of the doping level, the relationship between the doping-induced internal electric field and the anisotropy of the sample was studied. To understand the effect of the so-called doping oscillations, a theoretical model was developed. For the investigation of the thermal desorption of the III-V oxides in MOVPE, a number of test series were realised. It was also found that the formation of the reconstructed surface is finished a considerable time after the SE transient indicates stable conditions (no further reduction of the oxide layer). The activation energy for oxide desorption from InAs, GaAs and InP was

  5. Heterointegration of III-V on silicon using a crystalline oxide buffer layer (United States)

    Bhatnagar, K.; Rojas-Ramirez, J. S.; Contreras-Guerrero, R.; Caro, M.; Droopad, R.


    The integration of III-V compound semiconductors with Si can combine the cost advantage and maturity of Si technology with the superior performance of III-V materials. We have achieved the heteroepitaxial growth of III-V compound semiconductors on a crystalline SrTiO3 buffer layer grown on Si(0 0 1) substrates. A two-step growth process utilizing a high temperature nucleation layer of GaAs, followed by a low-temperature GaAs layer at a higher growth rate was employed to achieve highly crystalline thick GaAs layers on the SrTiO3/Si substrates with low surface roughness as seen by AFM. The effect of the GaAs nucleation layer on different surface terminations for the SrTiO3 layer was studied for both on axis and miscut wafers, which led to the conclusion that the Sr terminated surface on miscut substrates provides the best GaAs films. Using GaAs/STO/Si as virtual substrates, we have optimized the growth of high quality GaSb using the interfacial misfit (IMF) dislocation array technique. This work can lead to the possibility of realizing infrared detectors and next-generation high mobility III-V CMOS within the existing Si substrate infrastructure.

  6. Ion Implantation in III-V Compound Semiconductors (United States)


    340 keV H + -0 Ga P  O UES-723-292 !:• (H o>ray *P-K X - rayO Ga-K X -ray iii! RBS * ..I -iO.. 0 10I to1. 01 • .0 -. I0 1 LI =i, O I 0 01 0.J 10...Identity by blo ," pume) Ion Implantation, GaAs, Hall effect, electrical resistivity, Rutherford Backscattering (RBS), channeling, Proton induced x -ray...Mebility (jH) upon Aiinealing Temperature (TA) for 1 X 101 /cm• Dose Samples of GaAs:Mg with Three Different Capping Methods 33 p 14 Dependence of Surface

  7. Nonlinear Frequency Conversion in III-V Semiconductor Photonic Crystals (United States)


    Gonokami, R. H. Jordan, A. Dodabalapur, H. E. Katz , M. L. Schilling, R. E. Slusher, and S. Ozawa, “Polymer microdisk and microring lasers,” Opt. Lett...cavity,” Opt. Express, vol. 17, no. 25, pp. 22 689–22 703, 2009. [104] M. W. McCutcheon, G. W. Rieger, I. W. Cheung, J. F. Young, D. Dalacu, S. Frederick

  8. Growth far from equilibrium: Examples from III-V semiconductors (United States)

    Kuech, Thomas F.; Babcock, Susan E.; Mawst, Luke


    The development of new applications has driven the field of materials design and synthesis to investigate materials that are not thermodynamically stable phases. Materials which are not thermodynamically stable can be synthesized and used in many applications. These materials are kinetically stabilized during use. The formation of such metastable materials requires both an understanding of the associated thermochemistry and the key surface transport processes present during growth. Phase separation is most easily accomplished at the growth surface during synthesis where mass transport is most rapid. These surface transport processes are sensitive to the surface stoichiometry, reconstruction, and chemistry as well as the growth temperature. The formation of new metastable semiconducting alloys with compositions deep within a compositional miscibility gap serves as model systems for the understanding of the surface chemical and physical processes controlling their formation. The GaAs1-yBiy system is used here to elucidate the role of surface chemistry in the formation of a homogeneous metastable composition during the chemical vapor deposition of the alloy system.

  9. Asiago eclipsing binaries program. III. V570 Per

    CERN Document Server

    Tomasella, L; Cassisi, S; Siviero, A; Dallaporta, S; Sordo, R; Zwitter, T


    The orbit and physical parameters of the previously unsolved SB2 EB V570 Per are derived using high resolution Asiago Echelle spectroscopy and B, V photo-electric photometry. The metallicity from chi^2 analysis is [M/H]=+0.02 +/- 0.03, and reddening from interstellar NaI and KI absorption lines is E(B-V) =0.023 +/- 0.007. The two components have masses of 1.449 +/- 0.006 and 1.350 +/- 0.006 Msun and spectral types F3 and F5, respectively. They are both still within the Main Sequence band (T_1 =6842 +/- 25 K, T_2 =6562 +/- 25 K from chi^2 analysis, R_1 =1.523 +/- 0.030, R_2 =1.388 +/- 0.019 Rsun) and are dynamically relaxed to co-rotation with the orbital motion (Vrot sin i_{1,2} =40 and 36 (+/-1) km/sec). The distance to V570 Per obtained from the orbital solution is 123 +/- 2 pc, in excellent agreement with the revised Hipparcos distance of 123 +/- 11 pc. The observed properties of V570 Per components are compared to BaSTI models computed on purpose for exactly the observed masses and varied chemical composi...

  10. Dopant Profiling of III-V Nanostructures for Electronic Applications (United States)

    Ford, Alexandra Caroline


    High electron mobility III-V compound semiconductors such as indium arsenide (InAs) are promising candidates for future active channel materials of electron devices to further enhance device performance. In particular, compound semiconductors heterogeneously integrated on Si substrates have been studied, combining the high mobility of III-V semiconductors and the well-established, low cost processing of Si technology. However, one of the primary challenges of III-V device fabrication is controllable, post-growth dopant profiling. Here InAs nanowires and ultrathin layers (nanoribbons) on SiO2/Si are investigated as the channel material for high performance field-effect transistors (FETs) and post-growth, patterned doping techniques are demonstrated. First, the synthesis of crystalline InAs nanowires with high yield and tunable diameters by using Ni nanoparticles as the catalyst material on SiO 2/Si substrates is demonstrated. The back-gated InAs nanowire FETs have electron field-effect mobilities of ˜4,000 cm2/Vs and ION/IOFF ˜104. The uniformity of the InAs nanowires is demonstrated by large-scale assembly of parallel arrays of nanowires (˜400 nanowires) on SiO2/Si substrates by a contact printing process. This enables high performance, "printable" transistors with 5--10 mA ON currents. Second, an epitaxial transfer method for the integration of ultrathin layers of single-crystalline InAs on SiO2/Si substrates is demonstrated. As a parallel to silicon-on-insulator (SOI) technology, the abbreviation "XOI" is used to represent this compound semiconductor-on-insulator platform. A high quality InAs/dielectric interface is obtained by the use of a thermally grown interfacial InAsOx layer (˜1 nm thick). Top-gated FETs exhibit a peak transconductance of ˜1.6 mS/microm at V DS=0.5V with ION/I OFF >104 and subthreshold swings of 107--150 mV/decade for a channel length of ˜0.5 microm. Next, temperature-dependent I-V and C-V studies of single InAs nanowire FETs are

  11. Top-down Fabrication Technologies for High Quality III-V Nanostructures



    III-V nanostructures have attracted substantial research effort due to their interesting physical properties and their applications in new generation of ultrafast and high efficiency nanoscale electronic and photonic components. The advances in nanofabrication methods including growth/synthesis have opened up new possibilities of realizing one dimensional (1D) nanostructures as building blocks of future nanoscale devices. For processing of semiconductor nanostructure devices, simplicity, cost...

  12. Power-efficient III-V/silicon external cavity DBR lasers. (United States)

    Zilkie, A J; Seddighian, P; Bijlani, B J; Qian, W; Lee, D C; Fathololoumi, S; Fong, J; Shafiiha, R; Feng, D; Luff, B J; Zheng, X; Cunningham, J E; Krishnamoorthy, A V; Asghari, M


    We report the design and characterization of external-cavity DBR lasers built with a III-V-semiconductor reflective-SOA with spot-size converter edge-coupled to SOI waveguides containing Bragg grating mirrors. The un-cooled lasers have wall-plug-efficiencies of up to 9.5% at powers of 6 mW. The lasers are suitable for making power efficient, hybrid WDM transmitters in a CMOS-compatible SOI optical platform.

  13. High frequency III-V nanowire MOSFETs (United States)

    Lind, Erik


    III-V nanowire transistors are promising candidates for very high frequency electronics applications. The improved electrostatics originating from the gate-all-around geometry allow for more aggressive scaling as compared with planar field-effect transistors, and this can lead to device operation at very high frequencies. The very high mobility possible with In-rich devices can allow very high device performance at low operating voltages. GaN nanowires can take advantage of the large band gap for high voltage operation. In this paper, we review the basic physics and device performance of nanowire field- effect transistors relevant for high frequency performance. First, the geometry of lateral and vertical nanowire field-effect transistors is introduced, with special emphasis on the parasitic capacitances important for nanowire geometries. The basic important high frequency transistor metrics are introduced. Secondly, the scaling properties of gate-all-around nanowire transistors are introduced, based on geometric length scales, demonstrating the scaling possibilities of nanowire transistors. Thirdly, to model nanowire transistor performance, a two-band non-parabolic ballistic transistor model is used to efficiently calculate the current and transconductance as a function of band gap and nanowire size. The intrinsic RF metrics are also estimated. Finally, experimental state-of-the-art nanowire field-effect transistors are reviewed and benchmarked, lateral and vertical transistor geometries are explored, and different fabrication routes are highlighted. Lateral devices have demonstrated operation up to 350 GHz, and vertical devices up to 155 GHz.

  14. Surface Leakage Mechanisms in III-V Infrared Barrier Detectors (United States)

    Sidor, D. E.; Savich, G. R.; Wicks, G. W.


    Infrared detector epitaxial structures employing unipolar barriers exhibit greatly reduced dark currents compared to simple pn-based structures. When correctly positioned within the structure, unipolar barriers are highly effective at blocking bulk dark current mechanisms. Unipolar barriers are also effective at suppressing surface leakage current in infrared detector structures employing absorbing layers that possess the same conductivity type in their bulk and at their surface. When an absorbing layer possesses opposite conductivity types in its bulk and at its surface, unipolar barriers are not solutions to surface leakage. This work reviews empirically determined surface band alignments of III-V semiconductor compounds and modeled surface band alignments of both gallium-free and gallium-containing type-II strained layer superlattice material systems. Surface band alignments are used to predict surface conductivity types in several detector structures, and the relationship between surface and bulk conductivity types in the absorbing layers of these structures is used as the basis for explaining observed surface leakage characteristics.

  15. Valence band structure of binary chalcogenide vitreous semiconductors by high-resolution XPS

    Energy Technology Data Exchange (ETDEWEB)

    Kozyukhin, S., E-mail: [Russian Academy of Science, Institute of General and Inorganic Chemistry (Russian Federation); Golovchak, R. [Lviv Scientific Research Institute of Materials of SRC ' Carat' (Ukraine); Kovalskiy, A. [Lehigh University, Department of Materials Science and Engineering (United States); Shpotyuk, O. [Lviv Scientific Research Institute of Materials of SRC ' Carat' (Ukraine); Jain, H. [Lehigh University, Department of Materials Science and Engineering (United States)


    High-resolution X-ray photoelectron spectroscopy (XPS) is used to study regularities in the formation of valence band electronic structure in binary As{sub x}Se{sub 100-x}, As{sub x}S{sub 100-x}, Ge{sub x}Se{sub 100-x} and Ge{sub x}S{sub 100-x} chalcogenide vitreous semiconductors. It is shown that the highest occupied energetic states in the valence band of these materials are formed by lone pair electrons of chalcogen atoms, which play dominant role in the formation of valence band electronic structure of chalcogen-rich glasses. A well-expressed contribution from chalcogen bonding p electrons and more deep s orbitals are also recorded in the experimental valence band XPS spectra. Compositional dependences of the observed bands are qualitatively analyzed from structural and compositional points of view.

  16. Transferable tight binding model for strained group IV and III-V heterostructures (United States)

    Tan, Yaohua; Povolotskyi, Micheal; Kubis, Tillmann; Boykin, Timothy; Klimeck, Gerhard

    Modern semiconductor devices have reached critical device dimensions in the range of several nanometers. For reliable prediction of device performance, it is critical to have a numerical efficient model that are transferable to material interfaces. In this work, we present an empirical tight binding (ETB) model with transferable parameters for strained IV and III-V group semiconductors. The ETB model is numerically highly efficient as it make use of an orthogonal sp3d5s* basis set with nearest neighbor inter-atomic interactions. The ETB parameters are generated from HSE06 hybrid functional calculations. Band structures of strained group IV and III-V materials by ETB model are in good agreement with corresponding HSE06 calculations. Furthermore, the ETB model is applied to strained superlattices which consist of group IV and III-V elements. The ETB model turns out to be transferable to nano-scale hetero-structure. The ETB band structures agree with the corresponding HSE06 results in the whole Brillouin zone. The ETB band gaps of superlattices with common cations or common anions have discrepancies within 0.05eV.

  17. Surface properties and photocatalytic activity of KTaO3, CdS, MoS2 semiconductors and their binary and ternary semiconductor composites. (United States)

    Bajorowicz, Beata; Cybula, Anna; Winiarski, Michał J; Klimczuk, Tomasz; Zaleska, Adriana


    Single semiconductors such as KTaO3, CdS MoS2 or their precursor solutions were combined to form novel binary and ternary semiconductor nanocomposites by the calcination or by the hydro/solvothermal mixed solutions methods, respectively. The aim of this work was to study the influence of preparation method as well as type and amount of the composite components on the surface properties and photocatalytic activity of the new semiconducting photoactive materials. We presented different binary and ternary combinations of the above semiconductors for phenol and toluene photocatalytic degradation and characterized by X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area and porosity. The results showed that loading MoS2 onto CdS as well as loading CdS onto KTaO3 significantly enhanced absorption properties as compared with single semiconductors. The highest photocatalytic activity in phenol degradation reaction under both UV-Vis and visible light irradiation and very good stability in toluene removal was observed for ternary hybrid obtained by calcination of KTaO3, CdS, MoS2 powders at the 10:5:1 molar ratio. Enhanced photoactivity could be related to the two-photon excitation in KTaO3-CdS-MoS2 composite under UV-Vis and/or to additional presence of CdMoO4 working as co-catalyst.

  18. Cr-doped III-V nitrides: Potential candidates for spintronics

    KAUST Repository

    Amin, Bin


    Studies of Cr-doped III-V nitrides, dilute magnetic alloys in the zincblende crystal structure, are presented. The objective of the work is to investigate half-metallicity in Al 0.75Cr 0.25N, Ga 0.75Cr 0.25N, and In 0.75Cr 0.25N for their possible application in spin-based electronic devices. The calculated spin-polarized band structures, electronic properties, and magnetic properties of these compounds reveal that Al 0.75Cr 0.25N and Ga 0.75Cr 0.25N are half-metallic dilute magnetic semiconductors while In 0.75Cr 0.25N is metallic in nature. The present theoretical predictions provide evidence that some Cr-doped III-V nitrides can be used in spintronics devices. © 2011 TMS.

  19. Handbook of spintronic semiconductors

    CERN Document Server

    Chen, Weimin


    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.

  20. Progress Towards III-V Photovoltaics on Flexible Substrates (United States)

    McNatt, Jeremiah S.; Pal, AnnaMaria T.; Clark, Eric B.; Sayir, Ali; Raffaelle, Ryne P.; Bailey, Christopher G.; Hubbard, Seth M.; Maurer, William F.; Fritzemeier, Les


    Presented here is the recent progress of the NASA Glenn Research Center OMVPE group's efforts in the development of high efficiency thin-film polycrystalline III-V photovoltaics on optimum substrates. By using bulk polycrystalline germanium (Ge) films, devices of high efficiency and low mass will be developed and incorporated onto low-cost flexible substrates. Our progress towards the integration of high efficiency polycrystalline III-V devices and recrystallized Ge films on thin metal foils is discussed.

  1. Heralded single-photon source in a III-V photonic crystal. (United States)

    Clark, Alex S; Husko, Chad; Collins, Matthew J; Lehoucq, Gaelle; Xavier, Stéphane; De Rossi, Alfredo; Combrié, Sylvain; Xiong, Chunle; Eggleton, Benjamin J


    In this Letter we demonstrate heralded single-photon generation in a III-V semiconductor photonic crystal platform through spontaneous four-wave mixing. We achieve a high brightness of 3.4×10(7) pairs·s(-1) nm(-1) W(-1) facilitated through dispersion engineering and the suppression of two-photon absorption in the gallium indium phosphide material. Photon pairs are generated with a coincidence-to-accidental ratio over 60 and a low g(2) (0) of 0.06 proving nonclassical operation in the single photon regime.

  2. III-V/silicon photonic integrated circuits for communication and sensing applications (United States)

    Roelkens, Gunther; Keyvaninia, Shahram; Stankovic, Stevan; De Koninck, Yannick; Tassaert, Martijn; Mechet, Pauline; Spuesens, Thijs; Hattasan, N.; Gassenq, A.; Muneeb, M.; Ryckeboer, E.; Ghosh, Samir; Van Thourhout, D.; Baets, R.


    In this paper we review our work in the field of heterogeneous integration of III-V semiconductors and non-reciprocal optical materials on a silicon waveguide circuit. We elaborate on the heterogeneous integration technology based on adhesive DVS-BCB die-to-wafer bonding and discuss several device demonstrations. The presented devices are envisioned to be used in photonic integrated circuits for communication applications (telecommunications and optical interconnects) as well as in spectroscopic sensing systems operating in the short-wave infrared wavelength range.

  3. Surface Properties and Photocatalytic Activity of KTaO3, CdS, MoS2 Semiconductors and Their Binary and Ternary Semiconductor Composites

    Directory of Open Access Journals (Sweden)

    Beata Bajorowicz


    Full Text Available Single semiconductors such as KTaO3, CdS MoS2 or their precursor solutions were combined to form novel binary and ternary semiconductor nanocomposites by the calcination or by the hydro/solvothermal mixed solutions methods, respectively. The aim of this work was to study the influence of preparation method as well as type and amount of the composite components on the surface properties and photocatalytic activity of the new semiconducting photoactive materials. We presented different binary and ternary combinations of the above semiconductors for phenol and toluene photocatalytic degradation and characterized by X-ray powder diffraction (XRD, UV-Vis diffuse reflectance spectroscopy (DRS, scanning electron microscopy (SEM, Brunauer–Emmett–Teller (BET specific surface area and porosity. The results showed that loading MoS2 onto CdS as well as loading CdS onto KTaO3 significantly enhanced absorption properties as compared with single semiconductors. The highest photocatalytic activity in phenol degradation reaction under both UV-Vis and visible light irradiation and very good stability in toluene removal was observed for ternary hybrid obtained by calcination of KTaO3, CdS, MoS2 powders at the 10:5:1 molar ratio. Enhanced photoactivity could be related to the two-photon excitation in KTaO3-CdS-MoS2 composite under UV-Vis and/or to additional presence of CdMoO4 working as co-catalyst.

  4. Research progress of III-V laser bonding to Si (United States)

    Bo, Ren; Yan, Hou; Yanan, Liang


    The vigorous development of silicon photonics makes a silicon-based light source essential for optoelectronics' integration. Bonding of III-V/Si hybrid laser has developed rapidly in the last ten years. In the tireless efforts of researchers, we are privileged to see these bonding methods, such as direct bonding, medium adhesive bonding and low temperature eutectic bonding. They have been developed and applied to the research and fabrication of III-V/Si hybrid lasers. Some research groups have made remarkable progress. Tanabe Katsuaki of Tokyo University successfully implemented a silicon-based InAs/GaAs quantum dot laser with direct bonding method in 2012. They have bonded the InAs/GaAs quantum dot laser to the silicon substrate and the silicon ridge waveguide, respectively. The threshold current of the device is as low as 200 A/cm2. Stevan Stanković and Sui Shaoshuai successfully produced a variety of hybrid III-V/Si laser with the method of BCB bonding, respectively. BCB has high light transmittance and it can provide high bonding strength. Researchers of Tokyo University and Peking University have realized III-V/Si hybrid lasers with metal bonding method. We describe the progress in the fabrication of III-V/Si hybrid lasers with bonding methods by various research groups in recent years. The advantages and disadvantages of these methods are presented. We also introduce the progress of the growth of III-V epitaxial layer on silicon substrate, which is also a promising method to realize silicon-based light source. I hope that readers can have a general understanding of this field from this article and we can attract more researchers to focus on the study in this field.

  5. Hybrid III-V/SOI Resonant Cavity Photodetector

    DEFF Research Database (Denmark)

    Learkthanakhachon, Supannee; Taghizadeh, Alireza; Park, Gyeong Cheol;


    A hybrid III-V/SOI resonant cavity photo detector has been demonstrated, which comprises an InP grating reflectorand a Si grating reflector. It can selectively detects an incident light with 1.54-µm wavelength and TM polarization....

  6. Method of passivating semiconductor surfaces (United States)

    Wanlass, Mark W.


    A method of 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.

  7. Pre-patterned silicon substrates for the growth of III-V nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Benyoucef, M.; Usman, M.; Alzoubi, T.; Reithmaier, J.P. [Institute of Nanostructure Technologies and Analytics (INA), CINSaT, University of Kassel, Heinrich-Plett-Strasse 40, 34132 Kassel (Germany)


    This paper reviews the recent progresses obtained by direct growth of III-V semiconductor quantum dots (QDs) on pre-patterned and flat silicon substrates. This combination allows us to study in detail the growth mechanisms of III-V materials on silicon substrates. For the flat surfaces, we concentrate on basic growth studies addressing mainly morphological properties of QD-like structures with a main emphasis on surface preparation and growth parameters. For the pre-patterned substrates, we report the optimization of electron beam lithography and dry etching processes to fabricate sub-100 nm holes in pre-patterned Si (100) substrates with controlled size, shape, and periodicity. The pre-patterned silicon substrates underwent thorough ex situ chemical and in situ cleaning processes before the molecular beam epitaxy (MBE) growth. Finally, the MBE growth sequence of QDs on patterned silicon surface has shown highly selective formation of localized dome like nanostructures in patterned holes with 1 {mu}m period. A 3D AFM image of a single nanohole in silicon substrate with diameter and depth of about 70 nm. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Improved adhesion of photoresist to III-V substrates using PECVD carbon films (United States)

    Mancini, David P.; Smith, Steven M.; Hooper, Andrew F.; Talin, A.; Chang, Daniel; Resnick, Douglas J.; Voight, Steven A.


    Amorphous PECVD carbon films have been investigated as a means to prepare III-V compound semiconductor substrates for improved photoresist adhesion. Results show that significant improvements in adhesive durability of patterned photoresist occurred for carbon primed GaAs and InGaAs wafers used in conjunction with both i-line and DUV lithography processes. These carbon layers, were 50-100 Angstrom in thickness, and varied in composition and morphology from a nitrogen-doped, diamond-like material (DLC), to a more hydrogen rich, polymer-like material (PLC). Adhesion durability tests performed in baths of ammonium hydroxide (NH4OH) and hydrochloric acid (HCl) in general showed superior performance compared to non-primed substrates. The sole exception was a failure of PLC priming on GaAs wafers used with a DUV anti-reflective coating. This same system, however, was shown to work extremely well when a DLC coating was substituted. Characterization of PLC and DLC films included use of AES, XPS, FTIR, AFM, and contact angle analysis. Results indicate that carbon films passivate III-V oxides, creating a stable, hydrophobic surface. This factor is proposed as a key reason for the improved resistance to aggressive aqueous environments. AFM results show that carbon films are extremely smooth and actually decrease surface roughness, indicating that mechanical adhesion is unlikely.

  9. Method of fabricating vertically aligned group III-V nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Wang, George T; Li, Qiming


    A top-down method of fabricating vertically aligned Group III-V micro- and nanowires uses a two-step etch process that adds a selective anisotropic wet etch after an initial plasma etch to remove the dry etch damage while enabling micro/nanowires with straight and smooth faceted sidewalls and controllable diameters independent of pitch. The method enables the fabrication of nanowire lasers, LEDs, and solar cells.

  10. Design High-Efficiency III-V Nanowire/Si Two-Junction Solar Cell (United States)

    Wang, Y.; Zhang, Y.; Zhang, D.; He, S.; Li, X.


    In this paper, we report the electrical simulation results of a proposed GaInP nanowire (NW)/Si two-junction solar cell. The NW physical dimensions are determined for optimized solar energy absorption and current matching between each subcell. Two key factors (minority carrier lifetime, surface recombination velocity) affecting power conversion efficiency (PCE) of the solar cell are highlighted, and a practical guideline to design high-efficiency two-junction solar cell is thus provided. Considering the practical surface and bulk defects in GaInP semiconductor, a promising PCE of 27.5 % can be obtained. The results depict the usefulness of integrating NWs to construct high-efficiency multi-junction III-V solar cells.

  11. Efficient, tunable flip-chip-integrated III-V/Si hybrid external-cavity laser array. (United States)

    Lin, Shiyun; Zheng, Xuezhe; Yao, Jin; Djordjevic, Stevan S; Cunningham, John E; Lee, Jin-Hyoung; Shubin, Ivan; Luo, Ying; Bovington, Jock; Lee, Daniel Y; Thacker, Hiren D; Raj, Kannan; Krishnamoorthy, Ashok V


    We demonstrate a surface-normal coupled tunable hybrid silicon laser array for the first time using passively-aligned, high-accuracy flip chip bonding. A 2x6 III-V reflective semiconductor optical amplifier (RSOA) array with integrated total internal reflection mirrors is bonded to a CMOS SOI chip with grating couplers and silicon ring reflectors to form a tunable hybrid external-cavity laser array. Waveguide-coupled wall plug efficiency (wcWPE) of 2% and output power of 3 mW has been achieved for all 12 lasers. We further improved the performance by reducing the thickness of metal/dielectric stacks and achieved 10mW output power and 5% wcWPE with the same integration techniques. This non-invasive, one-step back end of the line (BEOL) integration approach provides a promising solution to high density laser sources for future large-scale photonic integrated circuits.

  12. Final Report: Vapor Transport Deposition for Thin Film III-V Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Boettcher, Shannon [Univ. of Oregon, Eugene, OR (United States); Greenaway, Ann [Univ. of Oregon, Eugene, OR (United States); Boucher, Jason [Univ. of Oregon, Eugene, OR (United States); Aloni, Shaul [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)


    Silicon, the dominant photovoltaic (PV) technology, is reaching its fundamental performance limits as a single absorber/junction technology. Higher efficiency devices are needed to reduce cost further because the balance of systems account for about two-thirds of the overall cost of the solar electricity. III-V semiconductors such as GaAs are used to make the highest-efficiency photovoltaic devices, but the costs of manufacture are much too high for non-concentrated terrestrial applications. The cost of III-V’s is driven by two factors: (1) metal-organic chemical vapor deposition (MOCVD), the dominant growth technology, employs expensive, toxic and pyrophoric gas-phase precursors, and (2) the growth substrates conventionally required for high-performance devices are monocrystalline III-V wafers. The primary goal of this project was to show that close-spaced vapor transport (CSVT), using water vapor as a transport agent, is a scalable deposition technology for growing low-cost epitaxial III-V photovoltaic devices. The secondary goal was to integrate those devices on Si substrates for high-efficiency tandem applications using interface nanopatterning to address the lattice mismatch. In the first task, we developed a CSVT process that used only safe solid-source powder precursors to grow epitaxial GaAs with controlled n and p doping and mobilities/lifetimes similar to that obtainable via MOCVD. Using photoelectrochemical characterization, we showed that the best material had near unity internal quantum efficiency for carrier collection and minority carrier diffusions lengths in of ~ 8 μm, suitable for PV devices with >25% efficiency. In the second task we developed the first pn junction photovoltaics using CSVT and showed unpassivated structures with open circuit photovoltages > 915 mV and internal quantum efficiencies >0.9. We also characterized morphological and electrical defects and identified routes to reduce those defects. In task three we grew epitaxial

  13. Epitaxial growth of III-V nitrides and phase separation and ordering in indium gallium nitride alloys (United States)

    Doppalapudi, Dharanipal

    The family of III-V nitrides are wide band-gap semiconductors with a broad range of opto-electronic applications in LEDs, laser diodes, UV detectors as well as high temperature/high frequency devices. Due to the lack of good quality native substrates, GaN is grown on foreign substrates that have a lattice and thermal mismatch with GaN. This results in a material with a high density of defects, which in turn adversely affects the opto-electronic properties of the epilayer. In this study, GaN films were epitaxially grown on various substrates (C-plane sapphire, A-plane sapphire, SiC and ZnO) by molecular beam epitaxy. Additionally, GaN homoepitaxy onto laterally overgrown thick GaN substrates was investigated. It was demonstrated that the polarity of the GaN film plays a major role in determining the properties of the films. The growth parameters were optimized to eliminate inversion domain boundaries, which result in domains of opposite polarity in the GaN lattice. For growth on A-plane sapphire, it was found that substrate nitridation and low temperature buffer deposition are critical in order to obtain good epitaxial growth, in spite of the relatively small mismatch between the film and substrate. A crystallographic model was developed to explain this observation. By optimizing growth parameters, GaN films with excellent structural, transport, optical and device properties were grown. The second part of this research involves growth of ternary alloys and superlattice structures, which are essential in the fabrication of many devices. It was found that the InN-GaN pseudo-binary system is not homogeneous over the entire composition range. Due to the mismatch between the tetrahedral radii of GaN and InN, InGaN alloys exhibited phase separation and long-range atomic ordering. Investigations of InxGa1-xN films grown over a wide range of compositions by XRD and TEM showed that the predominant strain relieving mechanism was phase separation in films with x > 0.2, and

  14. III-V-on-silicon multi-frequency lasers. (United States)

    Keyvaninia, S; Verstuyft, S; Pathak, S; Lelarge, F; Duan, G-H; Bordel, D; Fedeli, J-M; De Vries, T; Smalbrugge, B; Geluk, E J; Bolk, J; Smit, M; Roelkens, G; Van Thourhout, D


    Compact multi-frequency lasers are realized by combining III-V based optical amplifiers with silicon waveguide optical demultiplexers using a heterogeneous integration process based on adhesive wafer bonding. Both devices using arrayed waveguide grating routers as well as devices using ring resonators as the demultiplexer showed lasing with threshold currents between 30 and 40 mA and output powers in the order of a few mW. Laser operation up to 60°C is demonstrated. The small bending radius allowable for the silicon waveguides results in a short cavity length, ensuring stable lasing in a single longitudinal mode, even with relaxed values for the intra-cavity filter bandwidths.

  15. Graded core/shell semiconductor nanorods and nanorod barcodes (United States)

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


    Disclosed herein is a graded core/shell semiconductor nanorod having at least a first segment of a core of a Group II-VI, Group III-V or a Group IV semiconductor, a graded shell overlying the core, wherein the graded shell comprises at least two monolayers, wherein the at least two monolayers each independently comprise a Group II-VI, Group III-V or a Group IV semiconductor.

  16. Scalable, epitaxy-free fabrication of super-absorbing sparse III-V nanowire arrays for photovoltaic applications (Conference Presentation) (United States)

    Cheng, Wen-Hui; Fountaine, Katherine T.; Bukowsky, Colton R.; Atwater, Harry A.


    III-V compound semiconductor nanowire arrays are promising candidates for photovoltaics applications due to their high volumetric absorption. Uniform nanowire arrays exhibit high absorption at certain wavelengths due to strong coupling into lossy waveguide modes. Previously, simulations predicted near-unity, broadband absorption in sparse semiconductor nanowire arrays (Polymer-embedded wires are removed from the bulk InP substrate by a mechanical method that facilitates extensive reuse of a single bulk InP wafer to synthesize many polymer-embedded nanowire array thin films. Arrays containing multiple nanowire radii and tapered nanowires were successfully fabricated. For both designs, the polymer-embedded arrays achieved 90% broadband absorption (λ=400-900 nm) in less than 100 nm planar equivalence of InP. The addition of a silver back reflector increased this broadband absorption to 95%. The repeatable process of imprinting, etching and peeling to obtain many nanowire arrays from one single wafer represents an economical manufacturing route for high efficiency III-V photovoltaics. [1] K.T. Fountaine, C.G. Kendall, Harry A. Atwater, "Near-unity broadband absorption designs for semiconducting nanowire arrays via localized radial mode excitation," Opt. Exp. (2014).

  17. Propiedades electrónicas de semiconductores III-V sometidos a tensión uniaxial en la dirección [111]; un enfoque según el método tight-binding: II. Antimoniuros y Fosfuros

    Directory of Open Access Journals (Sweden)

    J. Juan Martín Mozo


    Full Text Available Empleando un esquema de cálculo tight-binding que usa una base de orbitales sp3s*d5, se estudian propiedades de la estructura electrónica de un grupo de materiales semiconductores IIIV los cuales son de interés para la tecnología de dispositivos electrónicos y optoelectrónicos. En específico, se analiza la influencia sobre estas propiedades de una tensión aplicada según la dirección cristalográfica [111], haciendo uso de una formulación presentada en la primera parte del trabajo [Mora-Ramos 2009]. Especial atención se presta a la inclusión del efecto de deformación interna de la red cristalina. Para cada material de los estudiados presentamos las dependencias de las brechas energéticas asociadas a los puntos ¿, X y L de la zona de Brillouin como funciones de la tensión uniaxial en AlP, InP, AlSb, GaSb, InSb. Asimismo, reportamos expresiones de ajuste para los valores de las principales brechas energéticas en esos cinco materiales. Se detecta una fuerte dependencia no lineal de estas magnitudes, así como de las masas efectivas de conducción, con la tensión.

  18. Methods for fabricating thin film III-V compound solar cell (United States)

    Pan, Noren; Hillier, Glen; Vu, Duy Phach; Tatavarti, Rao; Youtsey, Christopher; McCallum, David; Martin, Genevieve


    The present invention utilizes epitaxial lift-off in which a sacrificial layer is included in the epitaxial growth between the substrate and a thin film III-V compound solar cell. To provide support for the thin film III-V compound solar cell in absence of the substrate, a backing layer is applied to a surface of the thin film III-V compound solar cell before it is separated from the substrate. To separate the thin film III-V compound solar cell from the substrate, the sacrificial layer is removed as part of the epitaxial lift-off. Once the substrate is separated from the thin film III-V compound solar cell, the substrate may then be reused in the formation of another thin film III-V compound solar cell.

  19. Fullerene Molecules and Other Clusters of III-V Compounds (United States)

    Hira, Ajit; Auxier, John, II; Lucero, Melinda


    The goal of the our work is to derive geometries of fullerene-like cages and other clusters of atoms from groups III and V of the periodic table. Our previous research focused on Carbon Fullerenes and on GanAsn clusters (n = 1 thru 12). Our research group has made an original discovery about GanAsn clusters. In our work on nanotechnology to date, we used the hybrid ab initio methods of quantum chemistry to derive the different geometries for the clusters of interest. We also calculated binding energies, bond-lengths, ionization potentials, electron affinities and HOMO-LUMO gaps, and IR spectra for these geometries. Of particular significance was the magic number for GaAs cluster stability that we found at n = 8. This is important because materials containing controlled III-V nanostructures provide the capability of preparing new classes of materials with enhanced optical, magnetic, chemical sensor and photo-catalytic properties. The second phase of the investigation will examine the effects of confinement on the optical properties the clusters. It will be interesting to observe novel linear as well as nonlinear optical processes in them. The third phase of the investigation will focus on the improved design of solar cells based on the optical properties of the clusters.

  20. Epitaxial growth of three dimensionally structured III-V photonic crystal via hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Qiye; Kim, Honggyu; Zhang, Runyu; Zuo, Jianmin; Braun, Paul V., E-mail: [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Sardela, Mauro [Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Balaji, Manavaimaran; Lourdudoss, Sebastian; Sun, Yan-Ting [Laboratory of Semiconductor Materials, Department of Materials and Nano Physics, Royal Institute of Technology (KTH), Electrum 229, 164 40 Kista (Sweden)


    Three-dimensional (3D) photonic crystals are one class of materials where epitaxy, and the resultant attractive electronic properties, would enable new functionalities for optoelectronic devices. Here we utilize self-assembled colloidal templates to fabricate epitaxially grown single crystal 3D mesostructured Ga{sub x}In{sub 1−x}P (GaInP) semiconductor photonic crystals using hydride vapor phase epitaxy (HVPE). The epitaxial relationship between the 3D GaInP and the substrate is preserved during the growth through the complex geometry of the template as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy. XRD reciprocal space mapping of the 3D epitaxial layer further demonstrates the film to be nearly fully relaxed with a negligible strain gradient. Fourier transform infrared spectroscopy reflection measurement indicates the optical properties of the photonic crystal which agree with finite difference time domain simulations. This work extends the scope of the very few known methods for the fabrication of epitaxial III-V 3D mesostructured materials to the well-developed HVPE technique.

  1. Garnet-free optical circulators monolithically integrated on spatially modified III-V quantum wells

    CERN Document Server

    Aleahmad, Parinaz; Christodoulides, Demetrios; LiKamWa, Patrick


    Optical circulators are indispensable components in photonic networks that are aimed to route information in a unidirectional way among their N-ports1,2. In general, these devices rely on magneto-optical garnets3 with appreciable Verdet constants that are utilized in conjunction with other elements like permanent magnets, wave-plates, birefringent crystals and/or beam splitters. Consequently, these arrangements are typically bulky and hence not conducive to on-chip photonic integration4-6. Of interest would be to devise strategies through which miniaturized optical circulators can be monolithically fabricated on light-emitting semiconductor platforms by solely relying on physical properties that are indigenous to the material itself. By exploiting the interplay between non-Hermiticity and nonlinearity, here we demonstrate a new class of chip-scale circulators on spatially modified III-V quantum well systems. These garnet-free unidirectional structures are broadband (over 2.5 THz) at 1550 nm, effectively loss-...

  2. Micro-Hall magnetic sensors with high magnetic sensitivity based on III-V heterostructures (United States)

    Del Medico, S.; Benyattou, Taha; Guillot, Gerard; Venet, T.; Gendry, Michel; Tardy, Jacques; Chovet, Alain


    In this work, we propose solutions based on engineering of III-V heterostructures to develop new types of semiconductor magnetic sensors. These micro-Hall sensors use the properties of a 2D electron gas and the benefit of pseudomorphic material, in which both the alloy composition and the built-in strain offer additional degrees of freedom for band structure tailoring, to exhibit high magnetic sensitivity, good linearity, low temperature coefficient and high resolution. With the growth optimization which is described, two pseudomorphic In0.75Ga0.25As/In0.52Al0.48As heterostructures were grown on a semi- insulating InP substrate by molecular beam epitaxy. To understand better the influence of the heterostructure design on its electronic properties, a model involving the self-consistent solution of the Poisson and Schrodinger equations using the Fermi-Dirac statistics has been developed. These results have been used to optimize the structure design. A magnetic sensitivity of 346 V/AT with a temperature coefficient of -230 ppm/ degree(s)C between -80 degree(s)C and 85 degree(s)C has been obtained. The device show good linearity against magnetic field and also against the supply current. High signal-to-noise ratios corresponding to minimal magnetic field of 350 nT/Hz1/2 at 100 Hz and 120 nT/Hz1/2 at 1 kHz have been measured.

  3. Vertical III-V nanowire device integration on Si(100). (United States)

    Borg, Mattias; Schmid, Heinz; Moselund, Kirsten E; Signorello, Giorgio; Gignac, Lynne; Bruley, John; Breslin, Chris; Das Kanungo, Pratyush; Werner, Peter; Riel, Heike


    We report complementary metal-oxide-semiconductor (CMOS)-compatible integration of compound semiconductors on Si substrates. InAs and GaAs nanowires are selectively grown in vertical SiO2 nanotube templates fabricated on Si substrates of varying crystallographic orientations, including nanocrystalline Si. The nanowires investigated are epitaxially grown, single-crystalline, free from threading dislocations, and with an orientation and dimension directly given by the shape of the template. GaAs nanowires exhibit stable photoluminescence at room temperature, with a higher measured intensity when still surrounded by the template. Si-InAs heterojunction nanowire tunnel diodes were fabricated on Si(100) and are electrically characterized. The results indicate a high uniformity and scalability in the fabrication process.

  4. Analysis of novel silicon and III-V solar cells by simulation and experiment; Analyse neuartiger Silizium- und III-V-Solarzellen mittels Simulation und Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Hermle, Martin


    This work presents various simulation studies of silicon and III-V solar cells. For standard silicon solar cells, one of the critical parameters to obtain good performance, is the rear side recombination velocity. The optical and electrical differences of the different cell structures were determined. The optical differences and the effective recombination velocity Sback of the different rear side structures for 1 Ohmcm material were extracted. Beside standard silicon solar cells, back junction silicon solar cells were investigated. Especially the influence of the front surface field and the electrical shading due to the rear side, was investigated. In the last two chapters, III-V solar cells were analysed. For the simulation of III-V multi-junction solar cells, the simulation of the tunneldiode is the basic prerequisite. In this work, the numerical calibration of an GaAs tunneldiode was achieved by using an non-local tunnel model. Using this model, it was possible to successfully simulate a III-V tandem solar cell. The last chapter deals with an optimization of the III-V 3-junction cell for space applications. Especially the influence of the GaAs middle cell was investigated. Due to structural changes, the end-of-life efficiency was drastically increased.

  5. Genetic Algorithm for Innovative Device Designs in High-Efficiency III-V Nitride Light-Emitting Diodes (United States)

    Zhu, Di; Schubert, Martin F.; Cho, Jaehee; Schubert, E. Fred; Crawford, Mary H.; Koleske, Daniel D.; Shim, Hyunwook; Sone, Cheolsoo


    Light-emitting diodes are becoming the next-generation light source because of their prominent benefits in energy efficiency, versatility, and benign environmental impact. However, because of the unique polarization effects in III-V nitrides and the high complexity of light-emitting diodes, further breakthroughs towards truly optimized devices are required. Here we introduce the concept of artificial evolution into the device optimization process. Reproduction and selection are accomplished by means of an advanced genetic algorithm and device simulator, respectively. We demonstrate that this approach can lead to new device structures that go beyond conventional approaches. The innovative designs originating from the genetic algorithm and the demonstration of the predicted results by implementing structures suggested by the algorithm establish a new avenue for complex semiconductor device design and optimization.

  6. Thermodynamics of solid and liquid group III-V alloys

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, T.J.


    Solid-state electrochemical techniques are applied to the Ga-In-Sb-O system to measure some thermodynamic properties important for the analysis of solid-liquid phase equilibria in these important semiconductor materials. The standard Gibbs energies of formation of the most stable oxides of gallium and of indium are determined with a high-temperature solid-state electrochemical cell utilizing calcia-stabilized zirconia as the solid electrolyte and a (CO + CO/sub 2/) gaseous mixture as the reference electrode.

  7. Time Resolved Studies of Carrier Dynamics in III -v Heterojunction Semiconductors. (United States)

    Westland, Duncan James

    Available from UMI in association with The British Library. Requires signed TDF. Picosecond time-resolution photoluminescence spectroscopy has been used to study transient processes in Ga _{.47}In_{.53 }As/InP multiple quantum wells (MQWs), and in bulk Ga_{.47}In _{.53}As and GaSb. To facilitate the experimental studies, apparatus was constructed to allow the detection of transient luminescence with 3ps time resolution. A frequency upconversion technique was employed. Relaxation of energetic carriers in bulk Ga _{.47}In_{.53 }As by optic phonons has been investigated, and, at carrier densities ~3 times 10^{18}cm ^{-3} is found to be a considerably slower process than simple theory predicts. The discrepancy is resolved by the inclusion of a non-equilibrium population of longitudinal optic phonons in the theoretical description. Slow energy loss is also observed in a 154A MQW under similar conditions, but carriers are found to relax more quickly in a 14A MQW with a comparable repeat period. The theory of non-equilibrium mode occupation is modified to describe the case of a MQW and is found to agree with experiment. Carrier relaxation in GaSb is studied and the importance of occupation of the L _6 conduction band valley in this material is demonstrated. The ambipolar diffusion of a photoexcited carrier plasma through an InP capping layer was investigated using an optical time-of-flight technique. This experiment also enables the efficiency of carrier capture by a Ga _{.47}In_{.53 }As quantum well to be determined. A capture time of 4ps was found.

  8. Stable vapor transportation of solid sources in MOVPE of III V compound semiconductors (United States)

    Shenai-Khatkhate, Deodatta V.; DiCarlo, Ronald L.; Marsman, Charles J.; Polcari, Robert F.; Ware, Robert A.; Woelk, Egbert


    Trimethylindium (TMI), in spite of being a solid, has remained the precursor of choice for the deposition of indium containing layers by MOVPE. However, maintaining stable TMI flows and constant concentrations in gas phase during the growth still continue to be a major concern in MOVPE. This issue is further compounded by lower TMI consumptions achieved as the MOVPE growth conditions become increasingly more aggressive to meet the industry demand of higher throughputs, e.g. at higher flow rates, or at reduced pressures or when TMI source is maintained at higher temperatures. In this paper, we report our new findings of improved TMI delivery (>90, and in some cases >95%) with excellent stability of TMI concentration throughout the cylinder lifetime. These results are achieved using standard fill capacity and under intentionally set aggressive conditions of pressure, temperature and flow. We report a novel delivery technology (Uni-Flo™ II cylinder) that is customer proven and comprises innovative improvements to our dip-tube-less cylinder design, Uni-Flo™ cylinder, and advancements in TMI packaging. In this report, TMI depletion rates are examined over an extensive range of operating parameters currently employed in MOVPE, viz. flow rates ranging from 100 to 1000 sccm, source temperatures between 17 and 30 °C, and reactor pressures in the range 300-1000 mbar. We report, significant improvements in TMI delivery (>95% depletion) at higher molar flux of TMI (>3 g/h) and an excellent reproducible dosimetry of TMI with no batch-to-batch variation, by using Uni-Flo™ II cylinder as the enabling solution to TMI delivery problems.

  9. Low Temperature Photoluminescence Study of Holmium and Thulium Implanted into III-V Semiconductors and Silicon. (United States)


    Iwhere m* is the reduced mass formed from the nuclear mass and the electron or hole effective mass, and the other variables are as described for...Implanted Samples COND DOPING ANNEAL VENDOR3 TYPE TEMP/TIME/GAS n ? 750"C/15 min/N2 Wacker p B 750"C/15 min/N2 Reticon SI - 850"C/15 min/H2 MW SI

  10. III-V Semiconductor Quantum Well Lasers and Related Optoelectronic Devices (On Silicon) (United States)


    The laser fabrication begins with the patterning of for optoelectronic integrated circuits (OEICs), a planar 1 000 A of Si3N4 into rings [ grown in the center of the wave- guide in the lateral direction. guide layer. The effect of the optical waveguide is shown by the The laser ... fabrication begins with the deposition on the near-field (NF) pattern in the inset (b) of the -2-jim- crystal of - 1000 Ak Si 3N4, which is patterned with

  11. Growth and properties of low-dimensional III-V semiconductor nanowire heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Heiss, Martin


    In this work the properties of GaAs nanowire based heterostructures are investigated. The nanowires and their heterostructures are synthesized with Molecular Beam Epitaxy. The optical and structural properties are characterized by means of low temperature confocal micro-photoluminescence spectroscopy and Transmission Electron Microscopy. Molecular Beam Epitaxy is a versatile technique that allows to switch from radial to axial growth in order to cap the nanowires by an epitaxial prismatic AlGaAs/GaAs heterostructure. This can passivate surface states and improve the optical properties. The effect of such a passivation layer is studied by quantitative comparison of the diameter dependence of photoluminescence in passivated and unpassivated nanowires. The passivation is an important prerequisite for more complex axial heterostructures. Evidence for radial confinement effects is found in passivated nanowires with core diameters smaller than 70 nm. Furthermore, the polarization dependence of light absorption and emission is investigated. Two different types of axial heterostructures are studied that have the potential to further enhance the functionality of such nanowires. In a first step, the possibility of growth of axial InGaAs heterostructure in the Au-free Molecular Beam Epitaxy growth regime is investigated. Suitable growth conditions are identified and the growth temperature window for both GaAs and InGaAs nanowires is determined. At the optimum growth temperature for GaAs nanowires, the incorporation of indium in the structure is limited to a few percent. It is shown that by lowering the growth temperature the indium concentration in the structure can be increased up to 20%. The optical properties of the synthesized axial heterostructures are investigated by means of micro-photoluminescence spectroscopy and Transmission Electron Microscopy. The second type of axial nanowire heterostructure investigated in the present work is characterized by a change in crystal symmetry from cubic zinc-blende to hexagonal wurtzite structure, while the chemical composition of the material remains constant. The GaAs nanowires synthesized with the Au-free technique can be grown under conditions where a statistical wurtzite/zinc-blende polytypism occurs. A novel method for the direct correlation at the nanoscale of structural and optical properties of single GaAs nanowires is developed in order to characterize the resulting statistically distributed quantum heterostructures. Nanowires consisting of {approx}100% wurtzite and nanowires presenting zinc-blende/wurtzite polytypism are studied by photoluminescence spectroscopy and Transmission Electron Microscopy. The photoluminescence of wurtzite GaAs is found to be consistent with a bulk wurtzite band gap of 1.50 eV, slightly smaller compared to the zinc-blende GaAs band gap. In the polytypic nanowires, it is shown that the regions that are predominantly composed of either zinc-blende or wurtzite phase show photoluminescence emission close to the according bulk band gaps, while regions composed of a non periodic superlattice of wurtzite and zinc-blende phases exhibit a redshift of the photoluminescence spectra as low as 1.455 eV. The dimensions of the quantum heterostructures are correlated with the light emission, allowing us to estimate the band offsets of {delta}E{sub CB}=53{+-}20 meV and {delta}E{sub VB}=76{+-}12 meV between the two crystalline phases. These results are in excellent agreement with recent theoretical band structure calculations. (orig.)

  12. Investigation of Electrical and Optical Properties of Bulk III-V Ternary Semiconductors (United States)


    Japanese Journal of Applied Physics , vol. 33, part 1, no. 1A, pp. 28...of Hole Concentration,” Japanese Journal of Applied Physics , vol. 45, no. 8A, pp. 6373-6375, 2006. 30. Z. Fang, K. Ma, D. Jaw, R. Cohen, and G... Journal of Applied Physics , vol. 30, no. 6, pp. 1239-1242, 1991. 5. Important Issues on Film Deposition.

  13. Nanometer-Scale Compositional Structure in III-V Semiconductor Heterostructures Characterized by Scanning Tunneling Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Allerman, A.A.; Bi, W.G.; Biefeld, R.M.; Tu, C.W.; Yu, E.T.; Zuo, S.L.


    Nanometer-scale compositional structure in InAsxP1.InNYAsxPl.x-Y/InP, grown by gas-source molecular-beam epitaxy and in InAsl-xPJkAsl$b#InAs heterostructures heterostructures grown by metal-organic chemical vapor deposition has been characterized using cross-sectional scanning tunneling microscopy. InAsxP1-x alloy layers are found to contain As-rich and P-rich clusters with boundaries formed preferentially within (T 11) and (111) crystal planes. Similar compositional structure is observed within InNYAsxP1-x-Y alloy layers. Imaging of InAsl-xp@Asl#bY superlattices reveals nanometer-scale clustering within both the hAsI-.p and InAsl$bY alloy layers, with preferential alignment of compositional features in the direction. Instances are observed of compositional structure correlated across a heterojunction interface, with regions whose composition corresponds to a smaller unstrained lattice, constant relative to the surrounding alloy material appearing to propagate across the interface.

  14. Resonantly enhanced second-harmonic generation using III-V semiconductor all-dielectric metasurfaces

    CERN Document Server

    Liu, Sheng; Keeler, Gordon A; Sinclair, Michael B; Yang, Yuanmu; Reno, John; Pertsch, Thomas; Brener, Igal


    Nonlinear optical phenomena in nanostructured materials have been challenging our perceptions of nonlinear optical processes that have been explored since the invention of lasers. For example, the ability to control optical field confinement, enhancement, and scattering almost independently, allows nonlinear frequency conversion efficiencies to be enhanced by many orders of magnitude compared to bulk materials. Also, the subwavelength length scales render phase matching issues irrelevant. Compared with plasmonic nanostructures, dielectric resonator metamaterials show great promise for enhanced nonlinear optical processes due to their larger mode volumes. Here, we present, for the first time, resonantly enhanced second-harmonic generation (SHG) using Gallium Arsenide (GaAs) based dielectric metasurfaces. Using arrays of cylindrical resonators we observe SHG enhancement factors as large as 104 relative to unpatterned GaAs. At the magnetic dipole resonance we measure an absolute nonlinear conversion efficiency o...

  15. Theoretical Crystal-Field Calculations for Rare-Earth Ions in III-V semiconductor Compounds (United States)


    has recently generated a great deal of interest, motivated primarily by potential applications in optoelectronic devices. Many groups have reported...values again correspond to ionic charges larger than ±3. In general , it is more difficult to fit data measured in emission than in absorption, and it is...Washougal, WA 98671 Attn SLCHD-NW-TN, Chief Attn SLCHD-NW-TS, Chief Departmento Quimica Fundamental Attn SLCHD-PO, Chief Universidade Federal de

  16. The Surface Structure, Scattering Losses and Schottky Barrier Model of III-V Compound Semiconductors. (United States)


    CEN,CS2,CS4,CDS2,CDS4,CNi2 COMPLEX CN3 ,CN4 ,CN , CBETA, CMPLX, CATAN PRI-3. 14159625 CN1-CMPLX(3 .4700,-a .0005) CN2-1 .0 CN3-3.42 CN4-3.4 CN5-3.42 RK...CN1**2-CN5**2) *R**2...**2) CDS3-(- ) *CKX*CN3**2/CN1**2/CS3 CDS5-(-1) *CK*CN45**2/CNl**2/CS5 CFEMCKX=*A-P*PHI+ CATAN (-GUS 3) + CATAN (-GUS 5...0.002) 45 CS2-CSQRT(C(CN1**2-CGN2**2) *RJ**2...=**2) CS4-CSQRT ((CN1**2-CN4**2) *R**2-CCY**2) CDS2-(-.) *CKY/CS2 CDS4u(.)*K/CS4 CFKY-CX!*B-Q*PHI+ CATAN

  17. The Longwave Silicon Chip - Integrated Plasma-Photonics in Group IV And III-V Semiconductors (United States)


    collaboration on theory: Walter Buchwald, UMass Boston; Justin Cleary, AFRL; Joshua Hendrickson, AFRL; Jacob Khurgin, Johns Hopkins; Zoran Ikonic , Univ... Ikonic , “The direct and indirect bandgaps of SixGe1-x-ySny and their photonic device applications” Journal of Applied Physics, vol. 112, 073106

  18. Synthesis of Semiconductor Nanocrystals, Focusing on Nontoxic and Earth-Abundant Materials. (United States)

    Reiss, Peter; Carrière, Marie; Lincheneau, Christophe; Vaure, Louis; Tamang, Sudarsan


    We review the synthesis of semiconductor nanocrystals/colloidal quantum dots in organic solvents with special emphasis on earth-abundant and toxic heavy metal free compounds. Following the Introduction, section 2 defines the terms related to the toxicity of nanocrystals and gives a comprehensive overview on toxicity studies concerning all types of quantum dots. Section 3 aims at providing the reader with the basic concepts of nanocrystal synthesis. It starts with the concepts currently used to describe the nucleation and growth of monodisperse particles and next takes a closer look at the chemistry of the inorganic core and its interactions with surface ligands. Section 4 reviews in more detail the synthesis of different families of semiconductor nanocrystals, namely elemental group IV compounds (carbon nanodots, Si, Ge), III-V compounds (e.g., InP, InAs), and binary and multinary metal chalcogenides. Finally, the authors' view on the perspectives in this field is given.

  19. Growth and characterization of manganese doped III-V heterostructures; Herstellung und Charakterisierung von Mangan dotierten III-V Halbleiterheterostrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Wurstbauer, Ursula


    Subject of this thesis is the growth of III-V heterostructures doped with manganese by means of molecular beam epitaxy (MBE). The characterization was done primarily by magnetotransport measurements in the temperature range from 300 K to 20 mK and fields up to 19 T. Two different kind of Mn doped materials, ferromagnetic GaMnAs layers and Mn modulation doped magnetic two dimensional hole systems were studied. The first part focuses on the enhancement of the electric and magnetic properties of ferromagnetic properties and the integration of GaMnAs layers in more sophisticated heterostructures. Therefore, the crystal quality and the influence of the buffer layer beneath the magnetic layer are crucial. The MBE-growth of ferromagnetic GaMnAs layers on (001), (311)A and (311)A was successfully achieved with present values of the Curie-temperature (TC). Additionally, the growth of ferromagnetic GaMnAs layers on nonpolar (110) substrates and on cleaved [110] edges was established. An application of the latter was the investigation of magnetic bipolar junctions. Magnetic two dimensional hole gases (M2DHG) has been realized by the use of In0.75Al0.25As/In0.75Ga0.25As/InAs quantum well (QW) structures. It is necessary to grow a buffer layer for strain relaxation due to the lattice mismatch by gradually increasing the In mole fraction. Magnetotransport measurements were carried out on Si doped two-dimensional electron gases (2DEG) and on Mn doped M2DHGs. From magnetotransport measurements on the M2DHGs we see some interesting features, in particular in the mK region. From the 2DEGs and all non inverted doped M2DEGs weak localization and weak antilocalization effects can be observed in the low field region. Whereas all M2DHGs with an inverted doping layer show strong localization effects and a metal insulator transition dependent on the applied magnetic field perpendicular to the QW. In the high field region Shubnikov-de-Haas oscillations in the longitudinal resistance and

  20. High Efficiency Quantum Dot III-V Multijunction Solar Cell for Space Power Project (United States)

    National Aeronautics and Space Administration — We are proposing to utilize quantum dots to develop a super high-efficiency multijunction III-V solar cell for space. In metamorphic triple junction space solar...

  1. Engineering magnetism in semiconductors

    Directory of Open Access Journals (Sweden)

    Tomasz Dietl


    Full Text Available Transition metal doped III-V, II-VI, and group IV compounds offer an unprecedented opportunity to explore ferromagnetism in semiconductors. Because ferromagnetic spin-spin interactions are mediated by holes in the valence band, changing the Fermi level using co-doping, electric fields, or light can directly manipulate the magnetic ordering. Moreover, engineering the Fermi level position by co-doping makes it possible to modify solubility and self-compensation limits, affecting magnetic characteristics in a number of surprising ways. The Fermi energy can even control the aggregation of magnetic ions, providing a new route to self-organization of magnetic nanostructures in a semiconductor host.

  2. High temperature surface degradation of III-V nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Vartuli, C.B.; Pearton, S.J.; Abernathy, C.R.; MacKenzie, J.D.; Lambers, E.S. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States)


    The surface stoichiometry, surface morphology and electrical conductivity of AlN, GaN, InN, InGaN and InAlN was examined at rapid thermal annealing temperatures up to 1,150 C. The sheet resistance of the AlN dropped steadily with annealing, but the surface showed signs of roughening only above 1,000 C. Auger Electronic Spectroscopy (AES) analysis showed little change in the surface stoichiometry even at 1,150 C. GaN root mean square (RMS) surface roughness showed an overall improvement with annealing, but the surface became pitted at 1,000 C, at which point the sheet resistance also dropped by several orders of magnitude, and AES confirmed a loss of N from the surface. The InN surface had roughened considerably even at 650 C, and scanning electron microscopy (SEM) showed significant degradation. In contrast to the binary nitrides the sheet resistance of InAlN was found to increase by {approximately} 10{sup 2} from the as grown value after annealing at 800 C and then remain constant up to 1,000 C, while that of InGaN increased rapidly above 700 C. The RMS roughness increased above 800 C and 700 C respectively for InAlN and InGaN samples. In droplets began to form on the surface at 900 C for InAlN and at 800 C for InGaN, and then evaporate at 1,000 C leaving pits. AES analysis showed a decrease in the N concentration in the top 500 {angstrom} of the sample for annealing {ge} 800 C in both materials.

  3. III-V/Ge MOS device technologies for low power integrated systems (United States)

    Takagi, S.; Noguchi, M.; Kim, M.; Kim, S.-H.; Chang, C.-Y.; Yokoyama, M.; Nishi, K.; Zhang, R.; Ke, M.; Takenaka, M.


    CMOS utilizing high mobility III-V/Ge channels on Si substrates is expected to be one of the promising devices for high performance and low power integrated systems in the future technology nodes, because of the enhanced carrier transport properties. In addition, Tunneling-FETs (TFETs) using Ge/III-V materials are regarded as one of the most important steep slope devices for the ultra-low power applications. In this paper, we address the device and process technologies of Ge/III-V MOSFETs and TFETs on the Si CMOS platform. The channel formation, source/drain (S/D) formation and gate stack engineering are introduced for satisfying the device requirements. The plasma post oxidation to form GeOx interfacial layers is a key gate stack technology for Ge CMOS. Also, direct wafer bonding of ultrathin body quantum well III-V-OI channels, combined with Tri-gate structures, realizes high performance III-V n-MOSFETs on Si. We also demonstrate planar-type InGaAs and Ge/strained SOI TFETs. The defect-less p+-n source junction formation with steep impurity profiles is a key for high performance TFET operation.

  4. The Unexpected Influence of Precursor Conversion Rate in the Synthesis of III-V Quantum Dots. (United States)

    Franke, Daniel; Harris, Daniel K; Xie, Lisi; Jensen, Klavs F; Bawendi, Moungi G


    Control of quantum dot (QD) precursor chemistry has been expected to help improve the size control and uniformity of III-V QDs such as indium phosphide and indium arsenide. Indeed, experimental results for other QD systems are consistent with the theoretical prediction that the rate of precursor conversion is an important factor controlling QD size and size distribution. We synthesized and characterized the reactivity of a variety of group-V precursors in order to determine if precursor chemistry could be used to improve the quality of III-V QDs. Despite slowing down precursor conversion rate by multiple orders of magnitude, the less reactive precursors do not yield the expected increase in size and improvement in size distribution. This result disproves the widely accepted explanation for the shortcoming of current III-V QD syntheses and points to the need for a new generalizable theoretical picture for the mechanism of QD formation and growth.

  5. III-V/SOI vertical cavity laser structure for 120 Gbit/s speed

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Xue, Weiqi; Mørk, Jesper;


    Ultrashort-cavity structure for III-V/SOI vertical cavity laser with light output into a Si waveguide is proposed, enabling 17 fJ/bit efficiency or 120 Gbit/s speed. Experimentally, 27-GHz bandwidth is demonstrated at 3.5 times of threshold. © 2015 OSA.......Ultrashort-cavity structure for III-V/SOI vertical cavity laser with light output into a Si waveguide is proposed, enabling 17 fJ/bit efficiency or 120 Gbit/s speed. Experimentally, 27-GHz bandwidth is demonstrated at 3.5 times of threshold. © 2015 OSA....

  6. Design and Analysis of CMOS-Compatible III-V Compound Electron-Hole Bilayer Tunneling Field-Effect Transistor for Ultra-Low-Power Applications. (United States)

    Kim, Sung Yoon; Seo, Jae Hwa; Yoon, Young Jun; Lee, Ho-Young; Lee, Seong Min; Cho, Seongjae; Kang, In Man


    In this work, we design and analyze complementary metal-oxide-semiconductor (CMOS)-compatible III-V compound electron-hole bilayer (EHB) tunneling field-effect transistors (TFETs) by using two-dimensional (2D) technology computer-aided design (TCAD) simulations. A recently proposed EHB TFET exploits a bias-induced band-to-band tunneling (BTBT) across the electron-hole bilayer by an electric field from the top and bottom gates. This is in contrast to conventional planar p(+)-p(-)-n TFETs, which utilize BTBT across the source-to-channel junction. We applied III-V compound semiconductor materials to the EHB TFETs in order to enhance the current drivability and switching performance. Devices based on various compound semiconductor materials have been designed and analyzed in terms of their primary DC characteristics. In addition, the operational principles were validated by close examination of the electron concentrations and energy-band diagrams under various operation conditions. The simulation results of the optimally designed In0.533Ga0.47As EHB TFET show outstanding performance, with an on-state current (Ion) of 249.5 μA/μm, subthreshold swing (S) of 11.4 mV/dec, and threshold voltage (Vth) of 50 mV at VDS = 0.5 V. Based on the DC-optimized InGaAs EHB TFET, the CMOS inverter circuit was simulated in views of static and dynamic behaviors of the p-channel device with exchanges between top and bottom gates or between source and drain electrodes maintaining the device structure.

  7. Beyond CMOS: heterogeneous integration of III-V devices, RF MEMS and other dissimilar materials/devices with Si CMOS to create intelligent microsystems. (United States)

    Kazior, Thomas E


    Advances in silicon technology continue to revolutionize micro-/nano-electronics. However, Si cannot do everything, and devices/components based on other materials systems are required. What is the best way to integrate these dissimilar materials and to enhance the capabilities of Si, thereby continuing the micro-/nano-electronics revolution? In this paper, I review different approaches to heterogeneously integrate dissimilar materials with Si complementary metal oxide semiconductor (CMOS) technology. In particular, I summarize results on the successful integration of III-V electronic devices (InP heterojunction bipolar transistors (HBTs) and GaN high-electron-mobility transistors (HEMTs)) with Si CMOS on a common silicon-based wafer using an integration/fabrication process similar to a SiGe BiCMOS process (BiCMOS integrates bipolar junction and CMOS transistors). Our III-V BiCMOS process has been scaled to 200 mm diameter wafers for integration with scaled CMOS and used to fabricate radio-frequency (RF) and mixed signals circuits with on-chip digital control/calibration. I also show that RF microelectromechanical systems (MEMS) can be integrated onto this platform to create tunable or reconfigurable circuits. Thus, heterogeneous integration of III-V devices, MEMS and other dissimilar materials with Si CMOS enables a new class of high-performance integrated circuits that enhance the capabilities of existing systems, enable new circuit architectures and facilitate the continued proliferation of low-cost micro-/nano-electronics for a wide range of applications.

  8. On the Energy Momentum in Bianchi Type I-III-V-VI0 Space-Time

    CERN Document Server

    Aygun, S; Tarhan, I; Aygun, Melis; Aygun, Sezgin; Tarhan, Ismail


    In this study, using the energy momentum definitions of Einstein, Moller, Bergmann-Thomson, Landau-Lifshitz and Papapetrou we compute the total energy-momentum distribution (due to matter and fields including gravitation) of the universe based on general Bianchi type I-III-V-VI(o) space-time and its transforms type I, III, V, VI(o) metrics, respectively. The energy-momentum densities are found exactly same for Einstein and Bergmann-Thomson definitions. The total energy and momentum is found to be zero for Bianchi types I and VI(o) space-times. These results are same as a previous works of Radinschi, Banerjee-Sen, Xulu and Aydogdu-Salti. Another point is that our study agree with previous works of Cooperstock-Israelit, Rosen, Johri et al.

  9. MBE growth technology for high quality strained III-V layers (United States)

    Grunthaner, Frank J. (Inventor); Liu, John K. (Inventor); Hancock, Bruce R. (Inventor)


    III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group II and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation to low temperature, and to permit the film to relax to equilibrium. The method of the invention 1) minimizes starting step density on sample surface; 2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 mono-layers at a time); 3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and 4) uses time-resolved RHEED to achieve aspects (1)-14 (3).

  10. Nucleation and initial radius of self-catalyzed III-V nanowires (United States)

    Dubrovskii, V. G.; Borie, S.; Dagnet, T.; Reynes, L.; André, Y.; Gil, E.


    We treat theoretically the initial nucleation step of self-catalyzed III-V nanowires under simultaneously deposited group III and V vapor fluxes and with surface diffusion of a group III element. Our model is capable of describing the droplet size at which the very first nanowire monolayer nucleates depending on the element fluxes and surface temperature. This size determines the initial nanowire radius in growth techniques without pre-deposition of gallium. We show that useful self-catalyzed III-V nanowires can form only under the appropriately balanced V/III flux ratios and temperatures. Such balance is required to obtain nucleation from reasonably sized droplets that are neither too small under excessive arsenic flux nor too large in the arsenic-poor conditions.

  11. Low Thermal Budget Fabrication of III-V Quantum Nanostructures on Si Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bietti, S; Somaschini, C; Sanguinetti, S; Koguchi, N [L-NESS and Dipartimento di Scienza dei Materiali, via Cozzi 53, I-20125 Milano (Italy); Isella, G; Chrastina, D; Fedorov, A, E-mail: stefano.sanguinetti@mater.unimib.i [CNISM, L-NESS and Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, I-22100 Como (Italy)


    We show the possibility to integrate high quality III-V quantum nanostructures tunable in shape and emission energy on Si-Ge Virtual Substrate. Strong photoemission is observed, also at room temperature, from two different kind of GaAs quantum nanostructures fabricated on Silicon substrate. Due to the low thermal budget of the procedure used for the fabrication of the active layer, Droplet Epitaxy is to be considered an excellent candidate for implementation of optoelectronic devices on CMOS circuits.

  12. Graded core/shell semiconductor nanorods and nanorod barcodes (United States)

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


    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.

  13. Broadband and omnidirectional anti-reflection layer for III/V multi-junction solar cells

    CERN Document Server

    Diedenhofen, Silke L; Haverkamp, Erik; Bauhuis, Gerard; Schermer, John; Rivas, Jaime Gómez; 10.1016/j.solmat.2012.02.022


    We report a novel graded refractive index antireflection coating for III/V quadruple solar cells based on bottom-up grown tapered GaP nanowires. We have calculated the photocurrent density of an InGaP-GaAs-InGaAsP-InGaAs solar cell with a MgF2/ZnS double layer antireflection coating and with a graded refractive index coating. The photocurrent density can be increased by 5.9 % when the solar cell is coated with a graded refractive index layer with a thickness of 1\\mu m. We propose to realize such a graded refractive index layer by growing tapered GaP nanowires on III/V solar cells. For a first demonstration of the feasibility of the growth of tapered nanowires on III/V solar cells, we have grown tapered GaP nanowires on AlInP/GaAs substrates. We show experimentally that the reflection from the nanowire coated substrate is reduced and that the transmission into the substrate is increased for a broad spectral and angular range.

  14. III/V nano ridge structures for optical applications on patterned 300 mm silicon substrate (United States)

    Kunert, B.; Guo, W.; Mols, Y.; Tian, B.; Wang, Z.; Shi, Y.; Van Thourhout, D.; Pantouvaki, M.; Van Campenhout, J.; Langer, R.; Barla, K.


    We report on an integration approach of III/V nano ridges on patterned silicon (Si) wafers by metal organic vapor phase epitaxy (MOVPE). Trenches of different widths (≤500 nm) were processed in a silicon oxide (SiO2) layer on top of a 300 mm (001) Si substrate. The MOVPE growth conditions were chosen in a way to guarantee an efficient defect trapping within narrow trenches and to form a box shaped ridge with increased III/V volume when growing out of the trench. Compressively strained InGaAs/GaAs multi-quantum wells with 19% indium were deposited on top of the fully relaxed GaAs ridges as an active material for optical applications. Transmission electron microcopy investigation shows that very flat quantum well (QW) interfaces were realized. A clear defect trapping inside the trenches is observed whereas the ridge material is free of threading dislocations with only a very low density of planar defects. Pronounced QW photoluminescence (PL) is detected from different ridge sizes at room temperature. The potential of these III/V nano ridges for laser integration on Si substrates is emphasized by the achieved ridge volume which could enable wave guidance and by the high crystal quality in line with the distinct PL.

  15. Semimetal/Semiconductor Nanocomposites for Thermoelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Hong [Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Burke, Peter G. [Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Gossard, Arthur C. [Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Zeng, Gehong [Univ. of California, Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering; Ramu, Ashok T. [Univ. of California, Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering; Bahk, Je-Hyeong [Univ. of California, Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering; Bowers, John E. [Univ. of California, Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering


    In this work, we present research on semimetal-semiconductor nanocomposites grown by molecular beam epitaxy (MBE) for thermoelectric applications. We study several different III-V semiconductors embedded with semimetallic rare earth-group V (RE-V) compounds, but focus is given here to ErSb:InxGa1-xSb as a promising p-type thermoelectric material. Nano­structures of RE-V compounds are formed and embedded within the III-V semiconductor matrix. By codoping the nanocomposites with the appropriate dopants, both n-type and p-type materials have been made for thermoelectric applications. The thermoelectric properties have been engineered for enhanced thermoelectric device performance. Segmented thermoelectric power generator modules using 50 μm thick Er-containing nanocomposites have been fabricated and measured. Research on different rare earth elements for thermoelectrics is discussed.

  16. Metal-Insulator-Semiconductor Photodetectors

    Directory of Open Access Journals (Sweden)

    Chu-Hsuan Lin


    Full Text Available The major radiation of the Sun can be roughly divided into three regions: ultraviolet, visible, and infrared light. Detection in these three regions is important to human beings. The metal-insulator-semiconductor photodetector, with a simpler process than the pn-junction photodetector and a lower dark current than the MSM photodetector, has been developed for light detection in these three regions. Ideal UV photodetectors with high UV-to-visible rejection ratio could be demonstrated with III-V metal-insulator-semiconductor UV photodetectors. The visible-light detection and near-infrared optical communications have been implemented with Si and Ge metal-insulator-semiconductor photodetectors. For mid- and long-wavelength infrared detection, metal-insulator-semiconductor SiGe/Si quantum dot infrared photodetectors have been developed, and the detection spectrum covers atmospheric transmission windows.

  17. Integration of photodetectors with lasers for optical interconnects using 200 mm waferscale III-V/SOI technology

    DEFF Research Database (Denmark)

    Spuesens, Thijs; Liu, Liu; Vermeulen, Diedrik;


    We demonstrate efficient photodetectors on top of a laser epitaxial structure completely fabricated using 200 mm wafer scale III-V/SOI technology enabling very dense integration of lasers and detectors for optical interconnect circuits....

  18. Integrated Optical Pumping of Cr & Ti-Doped Sapphire Substrates With III-V Nitride Materials (United States)


    the Cr in sapphire could also permit the construction of white light LEDs . Ultimately, an integrated III-V Nitride optical pump for Ti:Sapphire could...substrates by MOCVD. 2. Characterization of doped sapphire/ InGaN structures byPL to simulate electrical injection by laser or LED device structures Part 2 1...Cr:sapphire substrate. Solid line is the spectrum of blue and red light emitted by InGaN LED epitaxially grown on Cr:sapphire substrate. The light was collected

  19. Silicon grating structures for optical fiber interfacing and III-V/silicon opto-electronic components (United States)

    Roelkens, Gunther; Vermeulen, Diedrik; Li, Yanlu; Muneeb, Muhammad; Hattasan, Nannicha; Ryckeboer, Eva; Deconinck, Yannick; Van Thourhout, Dries; Baets, Roel


    In this paper, we review our work on efficient, broadband and polarization independent interfaces between a silicon-on-insulator photonic IC and a single-mode optical fiber based on grating structures. The high alignment tolerance and the fact that the optical fiber interface is out-of-plane provide opportunities for easy packaging and wafer-scale testing of the photonic IC. Next to fiber-chip interfaces we will discuss the use of silicon grating structures in III-V on silicon optoelectronic components such as integrated photodetectors and microlasers.

  20. Morphology of interior interfaces in dilute nitride III/V material systems; Morphologie innerer Grenzflaechen in verduennt stickstoffhaltigen III/V-Materialsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Oberhoff, S.


    This study aims to clarify structure formation processes in dilute N-containing III/V-based material systems, using highly selective etching methods and subsequent atomic force microscopy (AFM) to expose and analyse interior interfaces. In the first part of this study it was directly proved for the first time that adding Sb during growth interruption inhibits the GI-induced structural phase transition and reduces the diffusivity on GaAs and (GaIn)(NAs) surfaces. However, applying Sb during GI does not affect the driving force of the structural phase transition. Therefore a fundamental analysis about the incorporation of Sb into GaAs, Ga(NAs) and (GaIn)(NAs) was carried out in the second part of the study. Using a combination of high resolution X-ray diffraction, transmission electron microscopy and SIMS measurements, it was verified that incorporating Sb into (GaIn)(NAs) causes an increase of the In content and a decrease of the N content. In the third part of the study, novel etching methods for the GaP-based material system Ga(NAsP) are introduced which provide the opportunity to analyse structure formation processes on interior interfaces in this material system by AFM. (orig.)

  1. III-V Semiconductor Quantum Well Lasers and Related Optoelectronic Devices (On Silicon). Oxide-Defined Semiconductor Quantum Well Lasers and Optoelectrnic Devices: A1-Based III-V Native Oxides (United States)


    lateral direction. guide layer. The effect of the optical waveguide is shown by the The laser fabrication begins with the deposition on the manipulate photons around a "chip," e.g., The laser fabrication begins with the patterning of for optoelectronic integrated circuits (OEICs), a

  2. Energy Momentum Localization for Bianchi I-III-V-VI0 Universe in Teleparallel Gravity

    CERN Document Server

    Aygun, S; Tarhan, I; Aygun, Melis; Aygun, Sezgin; Tarhan, Ismail


    In this paper, considering the tele-parallel gravity versions of the Einstein, Bergmann-Thomson and Landau-Lifshitz energy-momentum prescriptions energy and momentum distribution of the universe based on the general Bianchi type I-III-V-VI0 universe and its transforms type I, III, V, VI0 metrics, respectively which includes both the matter and gravitational fields are found. We obtain that Einstein and Bergmann-Thomson definitions of the energy-momentum complexes give the same results, while Landau-Lifshitz's energy-momentum definition does not provide same results for these type of metrics. This results are the same as a previous works of Aygun et al., the Authors investigate the same problem in general relativity by using the Einstein, Moller, Bergmann-Thomson, Landau-Lifshitz (LL) and Papapetrou's definitions. Furthermore, we show that for the Bianci type-I and type-VIo all the formulations give the same result. These results supports the viewpoints of Banerjee-Sen, Xulu and Aydogdu-Salti. Another point is...

  3. Cycloadditions to Epoxides Catalyzed by GroupIII-V Transition-Metal Complexes

    KAUST Repository

    D'Elia, Valerio


    Complexes of groupIII-V transition metals are gaining increasing importance as Lewis acid catalysts for the cycloaddition of dipolarophiles to epoxides. This review examines the latest reports, including homogeneous and heterogeneous applications. The pivotal step for the cycloaddition reactions is the ring opening of the epoxide following activation by the Lewis acid. Two modes of cleavage (C-C versus C-O) have been identified depending primarily on the substitution pattern of the epoxide, with lesser influence observed from the Lewis acid employed. The widely studied cycloaddition of CO2 to epoxides to afford cyclic carbonates (C-O bond cleavage) has been scrutinized in terms of catalytic efficiency and reaction mechanism, showing that unsophisticated complexes of groupIII-V transition metals are excellent molecular catalysts. These metals have been incorporated, as well, in highly performing, recyclable heterogeneous catalysts. Cycloadditions to epoxides with other dipolarophiles (alkynes, imines, indoles) have been conducted with scandium triflate with remarkable performances (C-C bond cleavage). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Study of the vertical transport in p-doped superlattices based on group III-V semiconductors

    Directory of Open Access Journals (Sweden)

    Sipahi Guilherme


    Full Text Available Abstract The electrical conductivity σ has been calculated for p-doped GaAs/Al0.3Ga0.7As and cubic GaN/Al0.3Ga0.7N thin superlattices (SLs. The calculations are done within a self-consistent approach to the k → ⋅ p → theory by means of a full six-band Luttinger-Kohn Hamiltonian, together with the Poisson equation in a plane wave representation, including exchange correlation effects within the local density approximation. It was also assumed that transport in the SL occurs through extended minibands states for each carrier, and the conductivity is calculated at zero temperature and in low-field ohmic limits by the quasi-chemical Boltzmann kinetic equation. It was shown that the particular minibands structure of the p-doped SLs leads to a plateau-like behavior in the conductivity as a function of the donor concentration and/or the Fermi level energy. In addition, it is shown that the Coulomb and exchange-correlation effects play an important role in these systems, since they determine the bending potential.

  5. Nucleation, propagation, electronic levels and elimination of misfit dislocations in III-V semiconductor interfaces. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Watson, G.P.; Matragrano, M.


    This report discusses the following topics: strained layer defects; the structural and electronic characteristics of misfit dislocations; requirements for the growth of high quality, low defect density InGaAs strained epitaxial layers; the isolation and nucleation of misfit dislocations in strained epitaxial layers grown on patterned, ion-damaged GaAs; the effect of pattern substrate trench depth on misfit dislocation density; the thermal stability of lattice mismatched InGaAs grown on patterned GaAs; misfit dislocations in ZnSe strained epitaxial layers grown on patterned GaAs; and the measurement of deep level states caused by misfit dislocations in InGaAs/GaAs grown on patterned GaAs substrates.

  6. Quasiparticle self-consistent GW theory of III-V nitride semiconductors: Bands, gap bowing, and effective masses

    DEFF Research Database (Denmark)

    Svane, Axel; Christensen, Niels Egede; Gorczyca, I.


    on the basis of the local approximation to density functional theory, although generally overestimated by 0.2–0.3 eV in comparison with experimental gap values. Details of the electronic energies and the effective masses including their pressure dependence are compared with available experimental information....... The band gap of InGaN2 is considerably smaller than what would be expected by linear interpolation implying a significant band gap bowing in InGaN alloys....

  7. [Structure and electronic properties of defects at nonlattice matched III-V semiconductor interfaces]. Progress report, 1989--90

    Energy Technology Data Exchange (ETDEWEB)

    Ast, D.G.


    Research focused on control of misfit dislocations in strained epitaxial layers of GaAs through prepatterning of the substrate. Patterning and etching trenches into GaAs substrates before epitaxial growth results in nonplanar wafer surface, which makes device fabrication more difficult. Selective ion damaging the substrate prior to growth was investigated. The question of whether the overlayer must or must not be discontinuous was addressed. The third research direction was to extend results from molecular beam epitaxially grown material to organometallic chemical vapor deposition. Effort was increased to study the patterning processes and the damage it introduces into the substrate. The research program was initiated after the discovery that 500-eV dry etching in GaAs damages the substrate much deeper than the ion range.

  8. Effect of low temperature anneals and nonthermal treatments on the properties of gap fill oxides used in SiGe and III-V devices (United States)

    Ryan, E. Todd; Morin, Pierre; Madan, Anita; Mehta, Sanjay


    Silicon dioxide is used to electrically isolate CMOS devices such as fin field effect transistors by filling gaps between the devices (also known as shallow trench isolation). The gap fill oxide typically requires a high temperature anneal in excess of 1000 °C to achieve adequate electrical properties and oxide densification to make the oxide compatible with subsequent fabrication steps such as fin reveal etch. However, the transition from Si-based devices to high mobility channel materials such as SiGe and III-V semiconductors imposes more severe thermal limitations on the processes used for device fabrication, including gap fill oxide annealing. This study provides a framework to quantify and model the effect of anneal temperature and time on the densification of a flowable silicon dioxide as measured by wet etch rate. The experimental wet etch rates allowed the determination of the activation energy and anneal time dependence for oxide densification. Dopant and self-diffusion can degrade the channel material above a critical temperature. We present a model of self-diffusion of Ge and Si in SiGe materials. Together these data allowed us to map the thermal process space for acceptable oxide wet etch rate and self-diffusion. The methodology is also applicable to III-V devices, which require even lower thermal budget. The results highlight the need for nonthermal oxide densification methods such as ultraviolet (UV) and plasma treatments. We demonstrate that several plasma treatments, in place of high temperature annealing, improved the properties of flowable oxide. In addition, UV curing prior to thermal annealing enables acceptable densification with dramatically reduced anneal temperature.

  9. Use of 3-aminopropyltriethoxysilane deposited from aqueous solution for surface modification of III-V materials

    Energy Technology Data Exchange (ETDEWEB)

    Knorr Jr, Daniel B., E-mail: [U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005, United States of America (United States); Williams, Kristen S. [U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005, United States of America (United States); Baril, Neil F. [U.S. Army, RDECOM, CERDEC, NVSED, Ft. Belvoir, VA 22060, United States of America (United States); Weiland, Conan [National Institute of Standards and Technology, Gaithersburg, MD 20899, United States of America (United States); Andzelm, Jan W. [U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005, United States of America (United States); Lenhart, Joseph L., E-mail: [U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005, United States of America (United States); Woicik, Joseph C.; Fischer, Daniel A. [National Institute of Standards and Technology, Gaithersburg, MD 20899, United States of America (United States); Tidrow, Meimei Z.; Bandara, Sumith V. [U.S. Army, RDECOM, CERDEC, NVSED, Ft. Belvoir, VA 22060, United States of America (United States); Henry, Nathan C. [U.S. Army, RDECOM, CERDEC, NVSED, Ft. Belvoir, VA 22060, United States of America (United States); Corbin Company, Alexandria, VA 22314, United States of America (United States)


    Graphical abstract: - Highlights: • HCl and citric acid showed excellent oxide removal on III/V surfaces. • Aminosilane (APTES) passivation coatings were deposited at 1–20 nm on InAs and GaSb. • These coatings showed high ionic nitrogen levels near the interface via XPS. • DFT was used to find adsorption energies of APTES with and without -OH groups. • DFT modeling showed APTES–NH{sub 3}{sup +} hydrogen abstraction to form surface -OH groups. - Abstract: Focal plane arrays of strained layer superlattices (SLSs) composed of InAs/GaSb are excellent candidates for infrared imaging, but one key factor limiting their utility is the lack of a surface passivation technique capable of protecting the mesa sidewall from degradation. Along these lines, we demonstrate the use of aqueous 3-aminopropyl triethoxysilane (APTES) deposited as a surface functionalizing agent for subsequent polymer passivation on InAs and GaSb surfaces following a HCl/citric acid procedure to remove the conductive oxide In{sub 2}O{sub 3}. Using atomic force microscopy, variable angle spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and modeling with density functional theory (DFT), we demonstrate that APTES films can successfully be deposited on III-V substrates by spin coating and directly compare these films to those deposited on silicon substrates. The HCl/citric acid surface preparation treatment is particularly effective at removing In{sub 2}O{sub 3} without the surface segregation of In oxides observed from use of HCl alone. However, HCl/citric acid surface treatment method does result in heavy oxidation of both Ga and Sb, accompanied by segregation of Ga oxide to the surface. Deposited APTES layer thickness did not depend on the substrate choice, and thicknesses between 1 and 20 nm were obtained for APTES solution concentrations ranging from 0.1 to 2.5 vol %. XPS results for the N1s band of APTES showed that

  10. Effective electron mass in quantum wires of III-V, ternary and quaternary materials. (United States)

    Paitya, N; Ghatak, K P


    In this paper, an attempt is made to study the effective electron mass (EEM) in Quantum wires (QWs) of III-V, ternary and quaternary materials on the basis of three and two band models of Kane within the framework of k x p formalism. It has been found, taking QWs of InAs, InSb, GaAs, Hg(1-x)Cd(x)Te and In(1-x)Ga(x)As(1-y)P(t) that the 1D EEM increases with electron concentration per unit length and decreases with increasing film thickness respectively. For ternary and quaternary materials the EEM increases with increase in alloy composition. Under certain special conditions all the results for all the 1-D materials get simplified into the well known parabolic energy bands and thus confirming the compatibility test. The results of this paper find two applications in the fields of nanoscience and technology.

  11. The MOCVD challenge a survey of GaInAsp-InP and GaInAsp-GaAs for photonic and electronic device applications

    CERN Document Server

    Razeghi, Manijeh


    Introduction to Semiconductor Compounds III-V semiconductor alloys III-V semiconductor devices Technology of multilayer growth Growth Technology Metalorganic chemical vapor deposition New non-equilibrium growth techniques In situ Characterization during MOCVD Reflectance anisotropy and ellipsometry Optimization of the growth of III-V binaries by RDS RDS investigation of III-V lattice-matched heterojunctions RDS investigation of III-V lattice-mismatched structures Insights on the growt

  12. Realization of back-side heterogeneous hybrid III-V/Si DBR lasers for silicon photonics (United States)

    Durel, Jocelyn; Ferrotti, Thomas; Chantre, Alain; Cremer, Sébastien; Harduin, Julie; Bernabé, Stéphane; Kopp, Christophe; Boeuf, Frédéric; Ben Bakir, Badhise; Broquin, Jean-Emmanuel


    In this paper, the simulation, design and fabrication of a back-side coupling (BSC) concept for silicon photonics, which targets heterogeneous hybrid III-V/Si laser integration is presented. Though various demonstrations of a complete SOI integration of passive and active photonic devices have been made, they all feature multi-level planar metal interconnects, and a lack of integrated light sources. This is mainly due to the conflict between the need of planar surfaces for III-V/Si bonding and multiple levels of metallization. The proposed BSC solution to this topographical problem consists in fabricating lasers on the back-side of the Si waveguides using a new process sequence. The devices are based on a hybrid structure composed of an InGaAsP MQW active area and a Si-based DBR cavity. The emitted light wavelength is accordable within a range of 20 nm around 1.31μm thanks to thermal heaters and the laser output is fiber coupled through a Grating Coupler (GC). From a manufacturing point of view, the BSC approach provides not only the advantages of allowing the use of a thin-BOX SOI instead of a thick one; but it also shifts the laser processing steps and their materials unfriendly to CMOS process to the far back-end areas of fabrication lines. Moreover, aside from solving technological integration issues, the BSC concept offers several new design opportunities for active and passive devices (heat sink, Bragg gratings, grating couplers enhanced with integrated metallic mirrors, tapers…). These building boxes are explored here theoretically and experimentally.

  13. Use of 3-aminopropyltriethoxysilane deposited from aqueous solution for surface modification of III-V materials (United States)

    Knorr, Daniel B., Jr.; Williams, Kristen S.; Baril, Neil F.; Weiland, Conan; Andzelm, Jan W.; Lenhart, Joseph L.; Woicik, Joseph C.; Fischer, Daniel A.; Tidrow, Meimei Z.; Bandara, Sumith V.; Henry, Nathan C.


    Focal plane arrays of strained layer superlattices (SLSs) composed of InAs/GaSb are excellent candidates for infrared imaging, but one key factor limiting their utility is the lack of a surface passivation technique capable of protecting the mesa sidewall from degradation. Along these lines, we demonstrate the use of aqueous 3-aminopropyl triethoxysilane (APTES) deposited as a surface functionalizing agent for subsequent polymer passivation on InAs and GaSb surfaces following a HCl/citric acid procedure to remove the conductive oxide In2O3. Using atomic force microscopy, variable angle spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and modeling with density functional theory (DFT), we demonstrate that APTES films can successfully be deposited on III-V substrates by spin coating and directly compare these films to those deposited on silicon substrates. The HCl/citric acid surface preparation treatment is particularly effective at removing In2O3 without the surface segregation of In oxides observed from use of HCl alone. However, HCl/citric acid surface treatment method does result in heavy oxidation of both Ga and Sb, accompanied by segregation of Ga oxide to the surface. Deposited APTES layer thickness did not depend on the substrate choice, and thicknesses between 1 and 20 nm were obtained for APTES solution concentrations ranging from 0.1 to 2.5 vol %. XPS results for the N1s band of APTES showed that the content of ionic nitrogen was high (∼50%) for the thinnest films (∼1 nm), and decreased with increasing film thickness. These results indicate that APTES can indeed be used to form a silane surface layer to cover III-V materials substrates. Such APTES silane layers may prove useful in surface passivation of these materials alone, or as surface functionalizing agents for subsequent covalent binding with polymer overlayers like polyimide.

  14. Electron beam pumped III-V nitride vertical cavity surface emitting lasers grown by molecular beam epitaxy (United States)

    Ng, Hock Min

    The design and fabrication by molecular beam epitaxy of a prototype vertical cavity laser based on the III-V nitrides were investigated in this work. The bottom mirror of the laser consists of distributed Bragg reflectors (DBRs) based on quarterwave AlN (or AlxGa1-xN) and GaN layers. Such DBRs were designed for maximum reflectivity in the spectral region from 390--600 nm. The epitaxial growth of these two binaries on each other revealed that while AlN grows on GaN in a two-dimensional mode (Frank-van der Merwe mode), GaN grows on AlN in a three-dimensional mode (Stranski-Krastanov mode). In spite of that, DBRs with peak reflectance up to 99% and bandwidths of 45nm were fabricated. The measured reflectance spectra were compared with simulations using the transmission matrix method. The mechanical stability of these DBR structures due to non-uniform distribution of strain arising from lattice or thermal mismatch of the various components were also addressed. The active region of the laser consists of InGaN/GaN multiple quantum wells (MQWs). The existence of up to the third order diffraction peaks in the x-ray diffraction spectra suggests that the interfaces between InGaN and GaN are sharp with little interdiffusion at the growth temperature. The photoluminescence and cathodoluminescence spectra were analyzed to determine the optical quality of the MQWs. The best MQWs were shown to have a single emission peak at 397nm with full width half maximum (FWHM) of 11nm. Cathodoluminescence studies showed that there are spatially localized areas of intense light emission. The complete device was formed on (0001) sapphire substrates using the previously described DBRs as bottom mirrors and the MQWs as the active region. The top mirror of the device consists of metallic silver. The device was pumped by an electron beam from the top mirror side and the light output was collected from the sapphire side. Measurements at 100K showed narrowing of the linewidth with increasing pump

  15. Nano-semiconductors devices and technology

    CERN Document Server

    Iniewski, Krzysztof


    With contributions from top international experts from both industry and academia, Nano-Semiconductors: Devices and Technology is a must-read for anyone with a serious interest in future nanofabrication technologies. Taking into account the semiconductor industry's transition from standard CMOS silicon to novel device structures--including carbon nanotubes (CNT), graphene, quantum dots, and III-V materials--this book addresses the state of the art in nano devices for electronics. It provides an all-encompassing, one-stop resource on the materials and device structures involved in the evolution

  16. High Efficiency Nanostructured III-V Photovoltaics for Solar Concentrator Application

    Energy Technology Data Exchange (ETDEWEB)

    Hubbard, Seth


    The High Efficiency Nanostructured III-V Photovoltaics for Solar Concentrators project seeks to provide new photovoltaic cells for Concentrator Photovoltaics (CPV) Systems with higher cell efficiency, more favorable temperature coefficients and less sensitivity to changes in spectral distribution. The main objective of this project is to provide high efficiency III-V solar cells that will reduce the overall cost per Watt for power generation using CPV systems.This work is focused both on a potential near term application, namely the use of indium arsenide (InAs) QDs to spectrally "tune" the middle (GaAs) cell of a SOA triple junction device to a more favorable effective bandgap, as well as the long term goal of demonstrating intermediate band solar cell effects. The QDs are confined within a high electric field i-region of a standard GaAs solar cell. The extended absorption spectrum (and thus enhanced short circuit current) of the QD solar cell results from the increase in the sub GaAs bandgap spectral response that is achievable as quantum dot layers are introduced into the i-region. We have grown InAs quantum dots by OMVPE technique and optimized the QD growth conditions. Arrays of up to 40 layers of strain balanced quantum dots have been experimentally demonstrated with good material quality, low residual stain and high PL intensity. Quantum dot enhanced solar cells were grown and tested under simulated one sun AM1.5 conditions. Concentrator solar cells have been grown and fabricated with 5-40 layers of QDs. Testing of these devices show the QD cells have improved efficiency compared to baseline devices without QDs. Device modeling and measurement of thermal properties were performed using Crosslight APSYS. Improvements in a triple junction solar cell with the insertion of QDs into the middle current limiting junction was shown to be as high as 29% under one sun illumination for a 10 layer stack QD enhanced triple junction solar cell. QD devices have strong

  17. Band structure effects on resonant tunneling in III-V quantum wells versus two-dimensional vertical heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Philip M., E-mail: [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Electronic Systems Laboratory, Georgia Tech Research Institute, Atlanta, Georgia 30332 (United States); Tarasov, Alexey; Joiner, Corey A.; Vogel, Eric M. [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Ready, W. Jud [Electronic Systems Laboratory, Georgia Tech Research Institute, Atlanta, Georgia 30332 (United States)


    Since the invention of the Esaki diode, resonant tunneling devices have been of interest for applications including multi-valued logic and communication systems. These devices are characterized by the presence of negative differential resistance in the current-voltage characteristic, resulting from lateral momentum conservation during the tunneling process. While a large amount of research has focused on III-V material systems, such as the GaAs/AlGaAs system, for resonant tunneling devices, poor device performance and device-to-device variability have limited widespread adoption. Recently, the symmetric field-effect transistor (symFET) was proposed as a resonant tunneling device incorporating symmetric 2-D materials, such as transition metal dichalcogenides (TMDs), separated by an interlayer barrier, such as hexagonal boron-nitride. The achievable peak-to-valley ratio for TMD symFETs has been predicted to be higher than has been observed for III-V resonant tunneling devices. This work examines the effect that band structure differences between III-V devices and TMDs has on device performance. It is shown that tunneling between the quantized subbands in III-V devices increases the valley current and decreases device performance, while the interlayer barrier height has a negligible impact on performance for barrier heights greater than approximately 0.5 eV.

  18. Monolithic integration of III-V nanowire with photonic crystal microcavity for vertical light emission. (United States)

    Larrue, Alexandre; Wilhelm, Christophe; Vest, Gwenaelle; Combrié, Sylvain; de Rossi, Alfredo; Soci, Cesare


    A novel photonic structure formed by the monolithic integration of a vertical III-V nanowire on top of a L3 two-dimensional photonic crystal microcavity is proposed to enhance light emission from the nanowire. The impact on the nanowire spontaneous emission rate is evaluated by calculating the spontaneous emission factor β, and the material gain at threshold is used as a figure of merit of this vertical emitting nanolaser. An optimal design is identified for a GaAs nanowire geometry with r = 155 nm and L~1.1 μm, where minimum gain at threshold (gth~13×10³ cm⁻¹) and large spontaneous emission factor (β~0.3) are simultaneously achieved. Modification of the directivity of the L3 photonic crystal cavity via the band-folding principle is employed to further optimize the far-field radiation pattern and to increase the directivity of the device. These results lay the foundation for a new approach toward large-scale integration of vertical emitting nanolasers and may enable applications such as intra-chip optical interconnects.

  19. Bifunctional redox flow battery - 2. V(III)/V(II)-L-cystine(O{sub 2}) system

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Y.H.; Xun, Y. [Research Institute of Chemical Defense, Beijing 100083 (China); Cheng, J.; Yang, Y.S. [Research Institute of Chemical Defense, Beijing 100083 (China); Beijing Science and Technology University, Beijing 100083 (China); Ma, P.H. [Full Cell R and D Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China)


    A new bifunctional redox flow battery (BRFB) system, V(III)/V(II) - L-cystine(O{sub 2}), was systematically investigated by using different separators. It is shown that during charge, water transfer is significantly restricted with increasing the concentration of HBr when the Nafion 115 cation exchange membrane is employed. The same result can be obtained when the gas diffusion layer (GDL) hot-pressed separator is used. The organic electro-synthesis is directly correlated with the crossover of vanadium. When employing the anion exchange membrane, the electro-synthesis efficiency is over 96% due to a minimal crossover of vanadium. When the GDL hot-pressed separator is applied, the crossover of vanadium and water transfer are noticeably prevented and the electro-synthesis efficiency of over 99% is obtained. Those impurities such as vanadium ions and bromine can be eliminated through the purification of organic electro-synthesized products. The purified product is identified to be L-cysteic acid by IR spectrum. The BRFB shows a favorable discharge performance at a current density of 20 mA cm{sup -2}. Best discharge performance is achieved by using the GDL hot-pressed separator. The coulombic efficiency of 87% and energy efficiency of about 58% can be obtained. The cause of major energy losses is mainly associated with the cross-contamination of anodic and cathodic active electrolytes. (author)

  20. Damage in III-V compounds during focused ion beam milling. (United States)

    Rubanov, S; Munroe, P R


    The damage layers generated in III-V compounds exposed to energetic gallium ions in a focused ion beam (FIB) instrument have been characterized by transmission electron microscopy (TEM). The damage on the side walls of the milled trenches is in the form of amorphous layers associated with direct amorphization from the gallium beam, rather than from redeposition of milled material. However, the damage on the bottom of the milled trenches is more complex. For InP and InAs the damage layers include the presence of crystalline phases resulting from recrystallization associated heating from the incident beam and gallium implantation. In contrast, such crystalline phases are not present in GaAs. The thicknesses of the damage layers are greater than those calculated from theoretical models of ion implantation. These differences arise because the dynamic nature of FIB milling means that the energetic ion beams pass through already damaged layers. In InP recoil phosphorus atoms also cause significant damage.

  1. Laser field induced optical gain in a group III-V quantum wire (United States)

    Saravanan, Subramanian; Peter, Amalorpavam John; Lee, Chang Woo


    Effect of intense high frequency laser field on the electronic and optical properties of heavy hole exciton in an InAsP/InP quantum well wire is investigated taking into consideration of the spatial confinement. Laser field induced exciton binding energies, optical band gap, oscillator strength and the optical gain in the InAs0.8P0.2/InP quantum well wire are studied. The variational formulism is applied to find the respective energies. The laser field induced optical properties are studied. The optical gain as a function of photon energy, in the InAs0.8P0.2/InP quantum wire, is obtained in the presence of intense laser field. The compact density matrix method is employed to obtain the optical gain. The results show that the 1.55 μm wavelength for the fibre optic telecommunication applications is achieved for 45 Å wire radius in the absence of laser field intensity whereas the 1.55 μm wavelength is obtained for 40 Å if the amplitude of the laser field amplitude parameter is 50 Å. The characterizing wavelength for telecommunication network is optimized when the intense laser field is applied for the system. It is hoped that the obtained optical gain in the group III-V narrow quantum wire can be applied for fabricating laser sources for achieving the preferred telecommunication wavelength.

  2. Impact of strain engineering on nanoscale strained III-V PMOSFETs. (United States)

    Chang, S T; Liu, Y C; Ou-Yang, H


    Stress distributions in the strained InGaAs PMOSFET with source/drain (S/D) stressors for various lengths and widths were studied with 3D stress simulations. The resulting mobility improvement was analyzed. Compressive stress along the transport direction was found to dominate the hole mobility improvement for the wide width devices. Stress along the vertical direction perpendicular to the gate oxide was found to affect the mobility the least, while stress along the width direction enhanced in the middle wide width region. The impact of channel width and length on performance improvements such as the mobility gain was analyzed using the Kubo-Greenwood formalism accounting for nonpolar hole-phonon scattering (acoustic and optical), surface roughness scattering, polar phonon scattering, alloy scattering and remote phonon scattering. The novelty of this paper is studying the impact of channel width and length on the performance of InGaAs PMOSFET such as mobility and exploring physical insight for scaling the future III-V CMOS devices.

  3. Proton irradiation effects on advanced digital and microwave III-V components

    Energy Technology Data Exchange (ETDEWEB)

    Hash, G.L.; Schwank, J.R.; Shaneyfelt, M.R.; Sandoval, C.E.; Connors, M.P.; Sheridan, T.J.; Sexton, F.W.; Slayton, E.M.; Heise, J.A. [Sandia National Labs., Albuquerque, NM (United States); Foster, C. [Indiana University Cyclotron Facility, Bloomington, IN (United States)


    A wide range of advanced III-V components suitable for use in high-speed satellite communication systems were evaluated for displacement damage and single-event effects in high-energy, high-fluence proton environments. Transistors and integrated circuits (both digital and MMIC) were irradiated with protons at energies from 41 to 197 MeV and at fluences from 10{sup 10} to 2 {times} 10{sup 14} protons/cm{sup 2}. Large soft-error rates were measured for digital GaAs MESFET (3 {times} 10{sup {minus}5} errors/bit-day) and heterojunction bipolar circuits (10{sup {minus}5} errors/bit-day). No transient signals were detected from MMIC circuits. The largest degradation in transistor response caused by displacement damage was observed for 1.0-{mu}m depletion- and enhancement-mode MESFET transistors. Shorter gate length MESFET transistors and HEMT transistors exhibited less displacement-induced damage. These results show that memory-intensive GaAs digital circuits may result in significant system degradation due to single-event upset in natural and man-made space environments. However, displacement damage effects should not be a limiting factor for fluence levels up to 10{sup 14} protons/cm{sup 2} [equivalent to total doses in excess of 10 Mrad(GaAs)].

  4. Fabrication of HfO2 patterns by laser interference nanolithography and selective dry etching for III-V CMOS application

    Directory of Open Access Journals (Sweden)

    Molina-Aldareguia Jon


    Full Text Available Abstract Nanostructuring of ultrathin HfO2 films deposited on GaAs (001 substrates by high-resolution Lloyd's mirror laser interference nanolithography is described. Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas. A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition. We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm. The exposed GaAs trenches were found to be residue-free and atomically smooth with a root-mean-square line roughness of 0.18 nm after plasma etching. PACS: Dielectric oxides 77.84.Bw, Nanoscale pattern formation 81.16.Rf, Plasma etching 52.77.Bn, Fabrication of III-V semiconductors 81.05.Ea


    Directory of Open Access Journals (Sweden)

    Soumen Banerjee,


    Full Text Available The effect of optically illumination of III-V compound semiconductor Indium Phosphide (InP and Wurtzite phase of Gallium Nitride (Wz-GaN or -GaN based Double Drift Impatt diodes at 300 GHz (0.3 THz has been investigated. The composition of photocurrent is altered by shining light on the p+ side and n+ side of the device through optical windows; thereby giving rise to Top Mounted (TM and Flip Chip (FC structures. The current multiplication factors for lectrons (Mn and for holes (Mp are altered to study the effect of leakage current in controlling the dynamic properties of the device. The conversion efficiency and output power of -GaN Impatt at 0.3 THz are 15.47% and 6.23 W respectively at an optimum bias current density of 0.5 x 108 A/m2 while the same parameters for InP Impatt are 18.38% and 2.81 W respectively at an optimum bias current density of 8.0 x 108 A/m2. Under optical illumination of the device, the frequency shift is observed to be more upwards upon lowering of Mpthan lowering of Mn. The frequency chirping in InP and -GaN Impatt are found to be of the order of few GHz, thereby indicating their high photo-sensitiveness at Sub-millimeter or Terahertz domain.

  6. Methods for forming group III-arsenide-nitride semiconductor materials (United States)

    Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)


    Methods are disclosed for forming Group III-arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

  7. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Veer Dhaka


    Full Text Available Low temperature (∼200 °C grown atomic layer deposition (ALD films of AlN, TiN, Al2O3, GaN, and TiO2 were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP nanowires (NWs, and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL at low temperatures (15K, and the best passivation was achieved with a few monolayer thick (2Å film. For InP NWs, the best passivation (∼2x enhancement in room-temperature PL was achieved with a capping of 2nm thick Al2O3. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al2O3 layer increased the carrier decay time from 251 ps (as-etched nanopillars to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al2O3 provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  8. Protective capping and surface passivation of III-V nanowires by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dhaka, Veer, E-mail:; Perros, Alexander; Kakko, Joona-Pekko; Haggren, Tuomas; Lipsanen, Harri [Department of Micro- and Nanosciences, Micronova, Aalto University, P.O. Box 13500, FI-00076 (Finland); Naureen, Shagufta; Shahid, Naeem [Research School of Physics & Engineering, Department of Electronic Materials Engineering, Australian National University, Canberra ACT 2601 (Australia); Jiang, Hua; Kauppinen, Esko [Department of Applied Physics and Nanomicroscopy Center, Aalto University, P.O. Box 15100, FI-00076 (Finland); Srinivasan, Anand [School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, S-164 40 Kista (Sweden)


    Low temperature (∼200 °C) grown atomic layer deposition (ALD) films of AlN, TiN, Al{sub 2}O{sub 3}, GaN, and TiO{sub 2} were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP) nanowires (NWs), and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL) at low temperatures (15K), and the best passivation was achieved with a few monolayer thick (2Å) film. For InP NWs, the best passivation (∼2x enhancement in room-temperature PL) was achieved with a capping of 2nm thick Al{sub 2}O{sub 3}. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al{sub 2}O{sub 3} layer increased the carrier decay time from 251 ps (as-etched nanopillars) to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al{sub 2}O{sub 3} provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  9. Low-power optically addressed spatial light modulators using MBE-grown III-V structures (United States)

    Maserjian, Joseph L.; Larsson, Anders G.


    Device approaches are investigated for O-SLMs based on MBE engineered III-V materials and structures. Strong photo-optic effects can be achieved in periodically (delta) -doped multiple quantum well (MQW) structures. The doping-defined barriers serve to separate and delay recombination of the photo-generated electron-hole pairs. One can use this photo-effect to change the internal field across the MQWs giving rise to quantum-confined Stark shift. Alternately, the photo-generated electrons can be used to occupy the quantum wells, which in turn causes exciton quenching and a shift of the absorption edge. Recent work has shown that both of these predicted photo-optic effects can indeed be achieved in such MBE engineered structures. However, these enhanced effects are still insufficient for high contrast modulation with only single or double pass absorption through active layers of practical thickness. We use the asymmetric Fabry-Perot cavity approach which permits extinction of light due to interference of light reflected from the front and back surfaces of the cavity. Modulation of the absorption in the active cavity layers unbalances the cavity and 'turns on' the reflected output signal, thereby allowing large contrast ratios. This approach is realized with an all-MBE- grown structure consisting of a GaAs/AlAs quarter-wave stack reflector grown over the GaAs substrate as the high reflectance mirror (approximately equals 0.98) and the GaAs surface as the low reflectance mirror (approximately equals 0.3). We use for our active cavities InGaAs/GaAs MQWs separated by npn (delta) -doped GaAs barriers to achieve sensitive photo-optic effect due to exciton quenching. High contrast modulation (> 60:1) is achieved with the Fabry-Perot structures using low power (write signal.

  10. Atomic Layer Deposited Thin Films for Dielectrics, Semiconductor Passivation, and Solid Oxide Fuel Cells (United States)

    Xu, Runshen

    Atomic layer deposition (ALD) utilizes sequential precursor gas pulses to deposit one monolayer or sub-monolayer of material per cycle based on its self-limiting surface reaction, which offers advantages, such as precise thickness control, thickness uniformity, and conformality. ALD is a powerful means of fabricating nanoscale features in future nanoelectronics, such as contemporary sub-45 nm metal-oxide-semiconductor field effect transistors, photovoltaic cells, near- and far-infrared detectors, and intermediate temperature solid oxide fuel cells. High dielectric constant, kappa, materials have been recognized to be promising candidates to replace traditional SiO2 and SiON, because they enable good scalability of sub-45 nm MOSFET (metal-oxide-semiconductor field-effect transistor) without inducing additional power consumption and heat dissipation. In addition to high dielectric constant, high-kappa materials must meet a number of other requirements, such as low leakage current, high mobility, good thermal and structure stability with Si to withstand high-temperature source-drain activation annealing. In this thesis, atomic layer deposited Er2O3 doped TiO2 is studied and proposed as a thermally stable amorphous high-kappa dielectric on Si substrate. The stabilization of TiO2 in its amorphous state is found to achieve a high permittivity of 36, a hysteresis voltage of less than 10 mV, and a low leakage current density of 10-8 A/cm-2 at -1 MV/cm. In III-V semiconductors, issues including unsatisfied dangling bonds and native oxides often result in inferior surface quality that yields non-negligible leakage currents and degrades the long-term performance of devices. The traditional means for passivating the surface of III-V semiconductors are based on the use of sulfide solutions; however, that only offers good protection against oxidation for a short-term (i.e., one day). In this work, in order to improve the chemical passivation efficacy of III-V semiconductors

  11. Low-Cost Growth of III-V Layers on Si Using Close-Spaced Vapor Transport

    Energy Technology Data Exchange (ETDEWEB)

    Boucher, Jason W.; Greenaway, Ann L.; Ritenour, Andrew J.; Davis, Allison L.; Bachman, Benjamin F.; Aloni, Shaul; Boettcher, Shannon W.


    Close-spaced vapor transport (CSVT) uses solid precursors to deposit material at high rates and with high precursor utilization. The use of solid precursors could significantly reduce the costs associated with III-V photovoltaics, particularly if growth on Si substrates can be demonstrated. We present preliminary results of the growth of GaAs1-xPx with x ≈ 0.3 and 0.6, showing that CSVT can be used to produce III-V-V’ alloys with band gaps suitable for tandem devices. Additionally, we have grown GaAs on Si by first thermally depositing films of Ge and subsequently depositing GaAs by CSVT. Patterning the Ge into islands prevents cracking due to thermal mismatch and is useful for potential tandem structures.

  12. Developing high-performance III-V superlattice IRFPAs for defense: challenges and solutions (United States)

    Zheng, Lucy; Tidrow, Meimei; Aitcheson, Leslie; O'Connor, Jerry; Brown, Steven


    The antimonide superlattice infrared detector technology program was established to explore new infrared detector materials and technology. The ultimate goal is to enhance the infrared sensor system capability and meet challenging requirements for many applications. Certain applications require large-format focal plane arrays (FPAs) for a wide field of view. These FPAs must be able to detect infrared signatures at long wavelengths, at low infrared background radiation, and with minimal spatial cross talk. Other applications require medium-format pixel, co-registered, dual-band capability with minimal spectral cross talk. Under the technology program, three leading research groups have focused on device architecture design, high-quality material growth and characterization, detector and detector array processing, hybridization, testing, and modeling. Tremendous progress has been made in the past few years. This is reflected in orders-of-magnitude reduction in detector dark-current density and substantial increase in quantum efficiency, as well as the demonstration of good-quality long-wavelength infrared FPAs. Many technical challenges must be overcome to realize the theoretical promise of superlattice infrared materials. These include further reduction in dark current density, growth of optically thick materials for high quantum efficiency, and elimination of FPA processing-related performance degradation. In addition, challenges in long-term research and development cost, superlattice material availability, FPA chip assembly availability, and industry sustainability are also to be met. A new program was established in 2009 with a scope that is different from the existing technology program. Called Fabrication of Superlattice Infrared FPA (FastFPA), this 4-year program sets its goal to establish U.S. industry capability of producing high-quality superlattice wafers and fabricating advanced FPAs. It uses horizontal integration strategy by leveraging existing III-V

  13. Gating a ferromagnetic semiconductor (United States)

    Bove, A.; Altomare, F.; Kundtz, N.; Chang, A. M.; Cho, Y. J.; Liu, X.; Furdyna, J.


    Ferromagnetic semiconductors have the potential of revolutionizing the way current electronic devices work: more so, because they are compatible with current fabrication lines and can easily be integrated with today's technology. Particular interest lies in III-V Diluted Magnetic Semiconductor (DMS), where the ferromagnetism is hole-mediated and the Curie temperature can therefore be tuned by changing the concentration of free carriers. In these systems, most of the effort is currently applied toward the fabrication of devices working at room-temperature: this implies high carrier density accompanied by low mobility and short mean free path. We will report our results for a ferromagnetic 2DHG system with low carrier density (˜3.4E12 cm-2) and mobility (˜ 1000 cm^2/(Vs)), and we will discuss the effects of local gating in light of possible applications to the fabrication of ferromagnetic quantum dots. T. Dietl et al., Phys. Rev. B 63, 195205 (2001). H. Ohno et al., Nature 408, 944 (2000)

  14. Technological development for super-high efficiency solar cells. Technological development for crystalline compound solar cells (high-efficiency III-V tandem solar cells); Chokokoritsu taiyo denchi no gijutsu kaihatsu. Kessho kagobutsu taiyo denchi no gijutsu kaihatsu (III-V zoku kagobutsu handotai taiyo denchi no gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    Tatsuta, M. [New Energy and Industrial Technology Development Organization, Tokyo (Japan)


    This paper reports the study results on technological development of III-V compound semiconductor solar cells in fiscal 1994. (1) On development of epitaxial growth technology of lattice mismatching systems, the optimum structure of InGaAs strain intermediate layers was studied for reducing a dislocation density by lattice mismatching of GaAs layer grown on Si substrate and difference in thermal expansion coefficient. The effect of strain layer on dislocation reduction was found only at 250dyne/cm in strain energy. Growth of GaAs layers on the Si substrate treated by hydrofluoric acid at low temperature was attempted by MBE method. As a dislocation distribution was controlled by laying different atoms at hetero-interface, the dislocation density of growing layer surfaces decreased by concentration of dislocation at hetero-interface. (2) On development of high-efficiency tandem cell structure, tunnel junction characteristics, cell formation process and optimum design method of lattice matching tandem cells were studied, while thin film cell formation was basically studied for lattice mismatching tandem cells. 45 figs., 8 tabs.

  15. Effective electron mass in low-dimensional semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Sitangshu [Indian Institute of Science, Bangalore (India). Nano Scale Device Research Lab.; Ghatak, Kamakhya Prasad [National Institute of Technology, Agartala, Tripura West (India). Dept. of Electronics and Communication Engineering


    Provides a treatment of the effective electron mass in nanodevices. Explains changes of the band structure of optoelectronic semiconductors by intense electric fields and light waves. Gives insight into the electronic behavior in doped semiconductors and their nanostructures. Supports tuition by 200 open problems and questions. This book deals with the Effective Electron Mass (EEM) in low dimensional semiconductors. The materials considered are quantum confined non-linear optical, III-V, II-VI, GaP, Ge, PtSb2, zero-gap, stressed, Bismuth, carbon nanotubes, GaSb, IV-VI, Te, II-V, Bi2Te3, Sb, III-V, II-VI, IV-VI semiconductors and quantized III-V, II-VI, IV-VI and HgTe/CdTe superlattices with graded interfaces and effective mass superlattices. The presence of intense electric field and the light waves change the band structure of optoelectronic semiconductors in fundamental ways, which have also been incorporated in the study of the EEM in quantized structures of optoelectronic compounds that control the studies of the quantum effect devices under strong fields. The importance of measurement of band gap in optoelectronic materials under strong electric field and external photo excitation has also been discussed in this context. The influence of crossed electric and quantizing magnetic fields on the EEM and the EEM in heavily doped semiconductors and their nanostructures is discussed. This book contains 200 open research problems which form the integral part of the text and are useful for both Ph. D aspirants and researchers in the fields of solid-state sciences, materials science, nanoscience and technology and allied fields in addition to the graduate courses in modern semiconductor nanostructures. The book is written for post graduate students, researchers and engineers, professionals in the fields of solid state sciences, materials science, nanoscience and technology, nanostructured materials and condensed matter physics.

  16. Coincident site lattice-matched growth of semiconductors on substrates using compliant buffer layers (United States)

    Norman, Andrew


    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 silicon substrate using a compliant buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The compliant buffer material and semiconductor materials may be deposited using 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 coincident site lattice matching epitaxial process, as well as the use of a ductile buffer material, reduce the internal stresses and associated crystal defects within the deposited semiconductor materials fabricated using the disclosed method. As a result, the semiconductor devices provided herein possess enhanced performance characteristics due to a relatively low density of crystal defects.

  17. Deviations from Vegard’s law in ternary III-V alloys

    KAUST Repository

    Murphy, S. T.


    Vegard’s law states that, at a constant temperature, the volume of an alloy can be determined from a linear interpolation of its constituent’s volumes. Deviations from this description occur such that volumes are both greater and smaller than the linear relationship would predict. Here we use special quasirandom structures and density functional theory to investigate such deviations for MxN1−xAs ternary alloys, where M and N are group III species (B, Al, Ga, and In). Our simulations predict a tendency, with the exception of AlxGa1−xAs, for the volume of the ternary alloys to be smaller than that determined from the linear interpolation of the volumes of the MAs and BAs binary alloys. Importantly, we establish a simple relationship linking the relative size of the group III atoms in the alloy and the predicted magnitude of the deviation from Vegard’s law.

  18. Optimized III-V Multijunction Concentrator Solar Cells on Patterned Si and Ge Substrates: Final Technical Report, 15 September 2004--30 September 2006

    Energy Technology Data Exchange (ETDEWEB)

    Ringel, S. A.


    Goal is to demo realistic path to III-V multijunction concentrator efficiencies > 40% by substrate-engineering combining compositional grading with patterned epitaxy for small-area cells for high concentration.

  19. Specific Approach for Size-Control III-V Quantum/Nano LED Fabrication for Prospective White Light Source (United States)


    The Final Report Title: Specific approach for size-control III-V based quantum/nano LED fabrication for prospective white ...COVERED 14-06-2005 to 14-12-2005 4. TITLE AND SUBTITLE Size controlled GaN based quantum dot LED for the prospective white light source 5a. CONTRACT...structure LED The physical model of the PC LED for optical simulation is shown in Figure 10. The LED are composed with p-type GaN/ MQW of InGaN /GaN/ n

  20. Effective Electron Mass in Low-Dimensional Semiconductors

    CERN Document Server

    Bhattacharya, Sitangshu


    This book deals with the Effective Electron Mass (EEM) in low dimensional semiconductors. The materials considered are quantum confined non-linear optical, III-V, II-VI, GaP, Ge, PtSb2, zero-gap, stressed, Bismuth, carbon nanotubes, GaSb, IV-VI, Te, II-V, Bi2Te3, Sb, III-V, II-VI, IV-VI semiconductors and quantized III-V, II-VI, IV-VI and HgTe/CdTe superlattices with graded interfaces and effective mass superlattices. The presence of intense electric field and the light waves change the band structure of optoelectronic semiconductors in fundamental ways, which have also been incorporated in the study of the EEM in quantized structures of optoelectronic compounds that control the studies of the quantum effect devices under strong fields. The importance of measurement of band gap in optoelectronic materials under strong electric field and external photo excitation has also been discussed in this context. The influence of crossed electric and quantizing magnetic fields on the EEM and the EEM in heavily doped sem...

  1. The electronic structure of impurities in semiconductors

    CERN Multimedia

    Nylandsted larsen, A; Svane, A


    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}$. \\\\ \\\\

  2. Addressing the electronic properties of III-V nanowires by photoluminescence excitation spectroscopy (United States)

    De Luca, M.


    Semiconductor nanowires (NWs) have been attracting an increasing interest in the scientific community. This is due to their peculiar filamentary shape and nanoscale diameter, which renders them versatile and cost-effective components of novel technological devices and also makes them an ideal platform for the investigation of a variety of fascinating physical effects. Absorption spectroscopy is a powerful and non-destructive technique able to provide information on the physical properties of the NWs. However, standard absorption spectroscopy is hard to perform in NWs, because of their small volume and the presence of opaque substrates. Here, we demonstrate that absorption can be successfully replaced by photoluminescence excitation (PLE). First, the use of polarization-resolved PLE to address the complex and highly-debated electronic band structure of wurtzite GaAs and InP NWs is shown. Then, PLE is used as a statistically-relevant method to localize the presence of separate wurtzite and zincblende NWs in the same InP sample. Finally, a variety of resonant exotic effects in the density of states of In x Ga1-x As/GaAs core/shell NWs are highlighted by high-resolution PLE. , which features invited work from the best early-career researchers working within the scope of J. Phys. D. This project is part of the Journal of Physics’ series 50th anniversary celebrations in 2017. Marta De Luca was selected by the Editorial Board of J. Phys. D as a Leader.

  3. Carrier transport in III-V quantum-dot structures for solar cells or photodetectors (United States)

    Wang, Wenqi; Wang, Lu; Jiang, Yang; Ma, Ziguang; Sun, Ling; Liu, Jie; Sun, Qingling; Zhao, Bin; Wang, Wenxin; Liu, Wuming; Jia, Haiqiang; Chen, Hong


    According to the well-established light-to-electricity conversion theory, resonant excited carriers in the quantum dots will relax to the ground states and cannot escape from the quantum dots to form photocurrent, which have been observed in quantum dots without a p-n junction at an external bias. Here, we experimentally observed more than 88% of the resonantly excited photo carriers escaping from InAs quantum dots embedded in a short-circuited p-n junction to form photocurrent. The phenomenon cannot be explained by thermionic emission, tunneling process, and intermediate-band theories. A new mechanism is suggested that the photo carriers escape directly from the quantum dots to form photocurrent rather than relax to the ground state of quantum dots induced by a p-n junction. The finding is important for understanding the low-dimensional semiconductor physics and applications in solar cells and photodiode detectors. Project supported by the National Natural Science Foundation of China (Grant Nos. 11574362, 61210014, 11374340, and 11474205) and the Innovative Clean-Energy Research and Application Program of Beijing Municipal Science and Technology Commission, China (Grant No. Z151100003515001).

  4. Analysis of the Si(111) surface prepared in chemical vapor ambient for subsequent III-V heteroepitaxy (United States)

    Zhao, W.; Steidl, M.; Paszuk, A.; Brückner, S.; Dobrich, A.; Supplie, O.; Kleinschmidt, P.; Hannappel, T.


    For well-defined heteroepitaxial growth of III-V epilayers on Si(111) substrates the atomic structure of the silicon surface is an essential element. Here, we study the preparation of the Si(111) surface in H2-based chemical vapor ambient as well as its atomic structure after contamination-free transfer to ultrahigh vacuum (UHV). Applying complementary UHV-based techniques, we derive a complete picture of the atomic surface structure and its chemical composition. X-ray photoelectron spectroscopy measurements after high-temperature annealing confirm a Si surface free of any traces of oxygen or other impurities. The annealing in H2 ambient leads to a monohydride surface termination, as verified by Fourier-transform infrared spectroscopy. Scanning tunneling microscopy confirms a well ordered, atomically smooth surface, which is (1 × 1) reconstructed, in agreement with low energy electron diffraction patterns. Atomic force microscopy reveals a significant influence of homoepitaxy and wet-chemical pretreatment on the surface morphology. Our findings show that wet-chemical pretreatment followed by high-temperature annealing leads to contamination-free, atomically flat Si(111) surfaces, which are ideally suited for subsequent III-V heteroepitaxy.

  5. A direct thin-film path towards low-cost large-area III-V photovoltaics. (United States)

    Kapadia, Rehan; Yu, Zhibin; Wang, Hsin-Hua H; Zheng, Maxwell; Battaglia, Corsin; Hettick, Mark; Kiriya, Daisuke; Takei, Kuniharu; Lobaccaro, Peter; Beeman, Jeffrey W; Ager, Joel W; Maboudian, Roya; Chrzan, Daryl C; Javey, Ali


    III-V photovoltaics (PVs) have demonstrated the highest power conversion efficiencies for both single- and multi-junction cells. However, expensive epitaxial growth substrates, low precursor utilization rates, long growth times, and large equipment investments restrict applications to concentrated and space photovoltaics (PVs). Here, we demonstrate the first vapor-liquid-solid (VLS) growth of high-quality III-V thin-films on metal foils as a promising platform for large-area terrestrial PVs overcoming the above obstacles. We demonstrate 1-3 μm thick InP thin-films on Mo foils with ultra-large grain size up to 100 μm, which is ~100 times larger than those obtained by conventional growth processes. The films exhibit electron mobilities as high as 500 cm²/V-s and minority carrier lifetimes as long as 2.5 ns. Furthermore, under 1-sun equivalent illumination, photoluminescence efficiency measurements indicate that an open circuit voltage of up to 930 mV can be achieved, only 40 mV lower than measured on a single crystal reference wafer.

  6. Advances in High-Efficiency III-V Multijunction Solar Cells

    Directory of Open Access Journals (Sweden)

    Richard R. King


    Full Text Available The high efficiency of multijunction concentrator cells has the potential to revolutionize the cost structure of photovoltaic electricity generation. Advances in the design of metamorphic subcells to reduce carrier recombination and increase voltage, wide-band-gap tunnel junctions capable of operating at high concentration, metamorphic buffers to transition from the substrate lattice constant to that of the epitaxial subcells, concentrator cell AR coating and grid design, and integration into 3-junction cells with current-matched subcells under the terrestrial spectrum have resulted in new heights in solar cell performance. A metamorphic Ga0.44In0.56P/Ga0.92In0.08As/ Ge 3-junction solar cell from this research has reached a record 40.7% efficiency at 240 suns, under the standard reporting spectrum for terrestrial concentrator cells (AM1.5 direct, low-AOD, 24.0 W/cm2, 25∘C, and experimental lattice-matched 3-junction cells have now also achieved over 40% efficiency, with 40.1% measured at 135 suns. This metamorphic 3-junction device is the first solar cell to reach over 40% in efficiency, and has the highest solar conversion efficiency for any type of photovoltaic cell developed to date. Solar cells with more junctions offer the potential for still higher efficiencies to be reached. Four-junction cells limited by radiative recombination can reach over 58% in principle, and practical 4-junction cell efficiencies over 46% are possible with the right combination of band gaps, taking into account series resistance and gridline shadowing. Many of the optimum band gaps for maximum energy conversion can be accessed with metamorphic semiconductor materials. The lower current in cells with 4 or more junctions, resulting in lower I2R resistive power loss, is a particularly significant advantage in concentrator PV systems. Prototype 4-junction terrestrial concentrator cells have been grown by metal-organic vapor-phase epitaxy, with preliminary measured

  7. Controlled growth of semiconductor crystals (United States)

    Bourret-Courchesne, Edith D.


    A method for growth of III-V, II-VI and related semiconductor single crystals that suppresses random nucleation and sticking of the semiconductor melt at the crucible walls. Small pieces of an oxide of boron B.sub.x O.sub.y are dispersed throughout the comminuted solid semiconductor charge in the crucible, with the oxide of boron preferably having water content of at least 600 ppm. The crucible temperature is first raised to a temperature greater than the melt temperature T.sub.m1 of the oxide of boron (T.sub.m1 K. for boron oxide B.sub.2 O.sub.3), and the oxide of boron is allowed to melt and form a reasonably uniform liquid layer between the crucible walls and bottom surfaces and the still-solid semiconductor charge. The temperature is then raised to approximately the melt temperature T.sub.m2 of the semiconductor charge material, and crystal growth proceeds by a liquid encapsulated, vertical gradient freeze process. About half of the crystals grown have a dislocation density of less than 1000/cm.sup.2. If the oxide of boron has water content less than 600 ppm, the crucible material should include boron nitride, a layer of the inner surface of the crucible should be oxidized before the oxide of boron in the crucible charge is melted, and the sum of thicknesses of the solid boron oxide layer and liquid boron oxide layer should be at least 50 .mu.m.

  8. Study on the impact of device parameter variations on performance of III-V homojunction and heterojunction tunnel FETs (United States)

    Hemmat, Maedeh; Kamal, Mehdi; Afzali-Kusha, Ali; Pedram, Massoud


    In this paper, the impact of physical parameter variations on the electrical characteristics of III-V TFETs is investigated. The study is performed on the operations of two optimized ultra-thin 20 nm double-gate transistors. The two device structures are InAs homojunction TFET and InAs-GaAs0.1Sb0.9 heterojunction TFET. The operation parameters are the ON-current, OFF-current, and threshold voltage. The investigation is performed at the device level, using a device simulator and the Monte-Carlo simulation approach is exploited to extract the distribution of electrical parameters in the presence of the process variation. The results reveal that the operation of the transistor is more sensitive to the doping of the source and gate work function compared to other physical parameters. Furthermore, the heterojunction TFETs show less sensitivity to physical parameter variations compared to the homojunction ones.

  9. A heterogeneous III-V/silicon integration platform for on-chip quantum photonic circuits with single quantum dot devices

    CERN Document Server

    Davanco, Marcelo; Sapienza, Luca; Zhang, Chen-Zhao; Cardoso, Jose Vinicius De Miranda; Verma, Varun; Mirin, Richard; Nam, Sae Woo; Liu, Liu; Srinivasan, Kartik


    Photonic integration is an enabling technology for photonic quantum science, offering greater scalability, stability, and functionality than traditional bulk optics. Here, we describe a scalable, heterogeneous III-V/silicon integration platform to produce Si$_3$N$_4$ photonic circuits incorporating GaAs-based nanophotonic devices containing self-assembled InAs/GaAs quantum dots. We demonstrate pure singlephoton emission from individual quantum dots in GaAs waveguides and cavities - where strong control of spontaneous emission rate is observed - directly launched into Si$_3$N$_4$ waveguides with > 90 % efficiency through evanescent coupling. To date, InAs/GaAs quantum dots constitute the most promising solidstate triggered single-photon sources, offering bright, pure and indistinguishable emission that can be electrically and optically controlled. Si$_3$N$_4$ waveguides offer low-loss propagation, tailorable dispersion and high Kerr nonlinearities, desirable for linear and nonlinear optical signal processing d...

  10. Growth and structural characterization of III-V nanowires grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Dheeraj, D.L.


    Heterostructured semiconductor nanowires (NWs) have attracted considerable attention in recent years because of their potential in future nano-electronic and nano-photonic device applications. NWs are usually grown by vapor-liquid-solid (VLS) growth mechanism using techniques such as metal-organic vapor phase epitaxy, chemical beam epitaxy and molecular beam epitaxy (MBE). Of all the available techniques, MBE is known to be the technique which yields highest purity materials. In this study, the growth of GaAs NWs, GaAsSb NWs, as well as GaAs/GaAsSb axial and GaAs/AlGaAs radial heterostructured NWs on GaAs(111)B substrates by MBE is demonstrated. The structural and optical properties of the NWs grown are characterized by electron microscopy techniques such as scanning and transmission electron microscopy, and micro-photoluminescence, respectively. Firstly, the optimum growth conditions to obtain rod shaped GaAs NWs on GaAs(111)B substrates by MBE is determined. It has been found that in-addition to the V/III ratio and substrate temperature, buffer growth conditions also play an important role on the orientation of the NWs. The effect of V/III ratio, substrate temperature, and the arsenic species (As{sub 2}/As{sub 4}) on the morphology of GaAs NWs has been determined. Transmission electron microscopy (TEM) characterization of NWs revealed that GaAs in NW form exhibit wurtzite (WZ) crystal phase in contrast to zinc blende (ZB) phase adapted in its bulk form. Since WZ crystal phase is a metastable phase of GaAs, the WZ GaAs NWs often exhibit stacking faults. The stacking faults are known to be a detrimental problem, if not properly controlled. To gain more insight on the growth kinetics of GaAs NWs grown by MBE, several samples such as GaAs NWs grown for different time durations, and GaAs NWs with three GaAsSb inserts, where GaAsSb inserts acts as markers, have been grown. Interestingly, the growth rates of the GaAs segments and GaAsSb inserts were observed to vary

  11. Hybrid III-V/SOI single-mode vertical-cavity laser with in-plane emission into a silicon waveguide

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Xue, Weiqi; Semenova, Elizaveta;


    We report a III-V-on-SOI vertical-cavity laser emitting into an in-plane Si waveguide fabricated by using CMOS-compatible processes. The fabricated laser operates at 1.54 µm with a SMSR of 33 dB and a low threshold.......We report a III-V-on-SOI vertical-cavity laser emitting into an in-plane Si waveguide fabricated by using CMOS-compatible processes. The fabricated laser operates at 1.54 µm with a SMSR of 33 dB and a low threshold....

  12. Implicit versus explicit momentum relaxation time solution for semiconductor nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Marin, E. G., E-mail:; Ruiz, F. G., E-mail:; Godoy, A., E-mail:; Tienda-Luna, I. M.; Gámiz, F. [Departamento de Electrónica, Universidad de Granada, Av. Fuentenueva S/N, 18071–Granada (Spain)


    We discuss the necessity of the exact implicit Momentum Relaxation Time (MRT) solution of the Boltzmann transport equation in order to achieve reliable carrier mobility results in semiconductor nanowires. Firstly, the implicit solution for a 1D electron gas with a isotropic bandstructure is presented resulting in the formulation of a simple matrix system. Using this solution as a reference, the explicit approach is demonstrated to be inaccurate for the calculation of inelastic anisotropic mechanisms such as polar optical phonons, characteristic of III-V materials. Its validity for elastic and isotropic mechanisms is also evaluated. Finally, the implications of the MRT explicit approach inaccuracies on the total mobility of Si and III-V NWs are studied.

  13. Polaronic trapping in magnetic semiconductors (United States)

    Raebiger, Hannes


    GaN doped with iron is an interesting candidate material for magnetic semiconductors, as p-d coupling between the localized Fe-d and extended N-p hole states is expected to facilitate long-range ferromagnetic alignment of the Fe spins [1]. This picture of extended states in GaN:Fe, however, falls apart due to a polaronic localization of the hole carriers nearby the Fe impurities. To elucidate the carrier localization in GaN:Fe and related iron doped III-V semiconductors, I present a systematic study using self-interaction corrected density-functional calculations [2]. These calculations predict three distinct scenarios. (i) Some systems do sustain extended host-like hole states, (ii) some exhibit polaronic trapping, (iii) and some exhibit carrier trapping at Fe-d orbitals. These behaviors are described in detail to give an insight as to how to distinguish them experimentally. I thank T. Fujita, C. Echeverria-Arrondo, and A. Ayuela for their collaboration.[4pt] [1] T. Dietl et al, Science, 287, 1019 (2000).[0pt] [2] S. Lany and A. Zunger, Phys. Rev. B, 80, 085202 (2009).

  14. Error-free Dispersion-uncompensated Transmission at 20 Gb/s over SSMF using a Hybrid III-V/SOI DML with MRR Filtering

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Kamchevska, Valerija; Ding, Yunhong;


    Error-free 20-Gb/s directly-modulated transmission is achieved by enhancing the dispersion tolerance of a III-V/SOI DFB laser with a silicon micro-ring resonator. Low (∼0.4 dB) penalty compared to back-to-back without ring is demonstrated after 5-km SSMF....

  15. Development and application of the S/PHI/nX library. First-principles calculations of thermodynamic properties of III-V semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Boeck, Sixten


    The objective of this thesis was the development and implementation of a new physics meta-language which simplifies the development of algorithms in computational materials design (CMD) significantly. (i) State-of- the-art computer science techniques have been applied or developed in this work to provide language elements to express algebraic expressions efficiently on modern computer platforms. (ii) Quantum mechanical algorithms are crucial in CMD. The new meta-language supports the Dirac notation to implement such algorithms in the native language of physicists. (iii) The language is completed by elements to express equations of motions efficiently which is required for implementing structural algorithms such as molecular dynamics. A major goal of this work was to combine an intuitive algebra/physics programming interface with high runtime performance. Therefore, a major challenge was to allow the compiler to ''understand'' the algebraic or even quantum mechanical context. Only with this knowledge the compiler can generate machine code which is (at least) as efficient as manually optimized code. This has been accomplished by deriving new techniques, such as fully automatic BLAS/LAPACK function mapping, algebra type mapping, and the application of sophisticated template techniques. Further details like memory management, efficiently exploiting the computer's level caches and arithmetic pipelines which had formerly to be addressed by physicists are in our approach entirely shifted to the compiler. With the new technique of virtual templates the compiler can now even detect the quantum mechanical context of Dirac elements. While Dirac projectors, scalar products with metrics, Dirac operators, and Dirac vectors look syntactically very similar, this technique allows the compiler to recognize these terms and generate the proper highly efficient function calls. Equations of motions can be intuitively expressed exploiting transformation pipelines which we developed in this work. In order to demonstrate the power of the this approach the full-featured plane-wave framework S/PHI/nX has been developed based on the new meta-language. The S/PHI/nX source code is remarkably short and transparent which simplifies code maintenance and the introduction of new sophisticated algorithms. Various benchmarks which have been conducted in this study compare S/PHI/nX with other state-of-the-art plane-wave packages with respect to runtime performance and accuracy. Based on these calculations we verified the general trends of phonon spectra, the location and amplitudes of the thermal anomalies of these systems. (orig.)

  16. Self-Aligned, Extremely High Frequency III-V Metal-Oxide-Semiconductor Field-Effect Transistors on Rigid and Flexible Substrates (United States)


    Goffman , M. F.; Bourgoin, J.-P. Appl. Phys. Lett. 2007, 90, 233108. (5) Nougaret, L.; Happy, H.; Dambrine, G.; Derycke, V.; Bourgoin, J.-P.; Green, A. A...Krishna, S.; Chueh, Y.-L.; Guo, J.; Javey, A. Nano Lett. 2012, 12, 2060−2066. (27) Chimot, N.; Derycke, V.; Goffman , M. F.; Bourgoin, J. P.; Happy, H

  17. Wet chemical functionalization of III-V semiconductor surfaces: alkylation of gallium arsenide and gallium nitride by a Grignard reaction sequence. (United States)

    Peczonczyk, Sabrina L; Mukherjee, Jhindan; Carim, Azhar I; Maldonado, Stephen


    Crystalline gallium arsenide (GaAs) (111)A and gallium nitride (GaN) (0001) surfaces have been functionalized with alkyl groups via a sequential wet chemical chlorine activation, Grignard reaction process. For GaAs(111)A, etching in HCl in diethyl ether effected both oxide removal and surface-bound Cl. X-ray photoelectron (XP) spectra demonstrated selective surface chlorination after exposure to 2 M HCl in diethyl ether for freshly etched GaAs(111)A but not GaAs(111)B surfaces. GaN(0001) surfaces exposed to PCl(5) in chlorobenzene showed reproducible XP spectroscopic evidence for Cl-termination. The Cl-activated GaAs(111)A and GaN(0001) surfaces were both reactive toward alkyl Grignard reagents, with pronounced decreases in detectable Cl signal as measured by XP spectroscopy. Sessile contact angle measurements between water and GaAs(111)A interfaces after various levels of treatment showed that GaAs(111)A surfaces became significantly more hydrophobic following reaction with C(n)H(2n-1)MgCl (n = 1, 2, 4, 8, 14, 18). High-resolution As 3d XP spectra taken at various times during prolonged direct exposure to ambient lab air indicated that the resistance of GaAs(111)A to surface oxidation was greatly enhanced after reaction with Grignard reagents. GaAs(111)A surfaces terminated with C(18)H(37) groups were also used in Schottky heterojunctions with Hg. These heterojunctions exhibited better stability over repeated cycling than heterojunctions based on GaAs(111)A modified with C(18)H(37)S groups. Raman spectra were separately collected that suggested electronic passivation by surficial Ga-C bonds at GaAs(111)A. Specifically, GaAs(111)A surfaces reacted with alkyl Grignard reagents exhibited Raman signatures comparable to those of samples treated with 10% Na(2)S in tert-butanol. For GaN(0001), high-resolution C 1s spectra exhibited the characteristic low binding energy shoulder demonstrative of surface Ga-C bonds following reaction with CH(3)MgCl. In addition, 4-fluorophenyl groups were attached and detected after reaction with C(6)H(4)FMgBr, further confirming the susceptibility of Cl-terminated GaN(0001) to surface alkylation. However, the measured hydrophobicities of alkyl-terminated GaAs(111)A and GaN(0001) were markedly distinct, indicating differences in the resultant surface layers. The results presented here, in conjunction with previous studies on GaP, show that atop Ga atoms at these crystallographically related surfaces can be deliberately functionalized and protected through Ga-C surface bonds that do not involve thiol/sulfide chemistry or gas-phase pretreatments.

  18. Nucleation, propagation, electronic levels and elimination of misfit dislocations in III-V semiconductor interfaces. Final report, September 1, 1986--August 31, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Ast, D.G.; Watson, G.P.; Matragrano, M.


    Misfit dislocations in gallium arsenides, indium arsenides, and zinc selenides are discussed. The growth of strained epitaxial layers, isolation and nucleation, thermal stability, and electronic and structural characteristics of misfit dislocations are described.

  19. Far from Equilibrium Vapour Phase Growth of Lattice Matched III-V Compound Semiconductor Interfaces: Some Basic Concepts and Monte-Carlo Computer Simulations, (United States)

    motivated particularly by the special conditions and considerations of importance to molecular beam epitaxial ( MBE ) growth of interfaces between tetrahedrally...presentation of a conceptual framework for MBE growth . This coherent presentation unfolds several kinetic aspects and their finer considerations which may by...defects and impurities, the surface migration kinetics, etc. in MBE growth . (Reprints)

  20. Magneto-electrical transport through MBE-grown III-V semiconductor nanostructures. From zero- to one-dimensional type of transport

    Energy Technology Data Exchange (ETDEWEB)

    Storace, Eleonora


    From the development of the first transistor in 1947, great interest has been directed towards the technological development of semiconducting devices and the investigation of their physical properties. A very vital field within this topic focuses on the electrical transport through low-dimensional structures, where the quantum confinement of charge carriers leads to the observation of a wide variety of phenomena that, in their turn, can give an interesting insight on the fundamental properties of the structures under examination. In the present thesis, we will start analyzing zero-dimensional systems, focusing on how electrons localized onto an island can take part in the transport through the whole system; by precisely tuning the tunnel coupling strength between this island and its surroundings, we will then show how it is possible to move from a zero- to a one-dimensional system. Afterwards, the inverse path will be studied: a one-dimensional system is electrically characterized, proving itself to split up due to disorder into several zero-dimensional structures. (orig.)

  1. Control de la forma, tamaño y composición de nanoestructuras de semiconductores III-V: anillos y puntos cuánticos


    González Taboada, Alfonso


    La epitaxia de haces moleculares (MBE) es una técnica de crecimiento extremadamente versátil que permite la obtención de películas delgadas cristalinas nanoestructuradas. En particular, los puntos cuánticos (QDs) de InAs en GaAs (001) han atraído la atención de numerosos grupos de investigación durante las dos últimas décadas.1 Los niveles discretos de energía característicos de esas nanoestructuras presentan una fuerte dependencia con el tamaño, composición y morfología de las mismas. ...

  2. III-V tri-gate quantum well MOSFET: Quantum ballistic simulation study for 10 nm technology and beyond (United States)

    Datta, Kanak; Khosru, Quazi D. M.


    In this work, quantum ballistic simulation study of a III-V tri-gate MOSFET has been presented. At the same time, effects of device parameter variation on ballistic, subthreshold and short channel performance is observed and presented. The ballistic simulation result has also been used to observe the electrostatic performance and Capacitance-Voltage characteristics of the device. With constant urge to keep in pace with Moore's law as well as aggressive scaling and device operation reaching near ballistic limit, a full quantum transport study at 10 nm gate length is necessary. Our simulation reveals an increase in device drain current with increasing channel cross-section. However short channel performance and subthreshold performance get degraded with channel cross-section increment. Increasing device cross-section lowers threshold voltage of the device. The effect of gate oxide thickness on ballistic device performance is also observed. Increase in top gate oxide thickness affects device performance only upto a certain value. The thickness of the top gate oxide however shows no apparent effect on device threshold voltage. The ballistic simulation study has been further used to extract ballistic injection velocity of the carrier and ballistic carrier mobility in the channel. The effect of device dimension and gate oxide thickness on ballistic velocity and effective carrier mobility is also presented.

  3. Deep in situ dry-etch monitoring of III-V multilayer structures using laser reflectometry and reflectivity modeling

    CERN Document Server

    Moussa, H; Meriadec, C; Manin, L; Sagnes, I; Raj, R


    Deep reactive ion etching of III-V multilayer structures is an important issue for long wavelength vertical cavity surface emitting laser (VCSELs) where full laser structures are usually very thick. Test etchings were performed on GaAs/Al sub x Ga sub 1 sub - sub x As Bragg mirror structures and monitored using laser reflectometry at 651.4 nm. In order to perform very deep etching, up to 9 mu m, we designed and fabricated a special two-level mask made up of a thick nitride layer and a thin nickel layer. The etching rate is a complex function of many parameters and may change from run to run for similar structures. Therefore, it is important to have a method to control accurately the process in situ by continuously matching, experimental curves with the results of the reflectivity modeling. Here, we present a model, based on the Abeles matrix method, of the normal incidence reflectivity of a multilayer stack as a function of etch depth. Comparison between the model and the observed reflectivity variation durin...

  4. Interface simulation of strained and non-abrupt III-V quantum wells. Part 1: band profile calculation (United States)

    Lamberti, C.


    This work presents a program, based on the Van de Walle-Martin model solid theory, able to compute the most important physical quantities of any In 1- xGa xAs yP 1- y quaternary epitaxially strained growth on any In 1- zGa zAs wP 1- w hypothetical substrate. The adopted interface-band alignment procedure is extensively described. The effect of strain on several examples of ideal heterostructures characterized by abrupt interfaces is discussed in detail. Furthermore, the problem of a composition gradient spread over some monolayers at the interfaces of III-V quantum wells and superlattices, due to the technological problems in group V switches in the present epitaxial techniques is treated extensively. The interface layers are thus non-intentionally strained on the substrate lattice parameter causing a local change in the bands profile along the growth direction. The differences between an ideal rectangular potential and the real profile are shown. The output files of this program consist in the band profiles for electrons, heavy and light holes, which will be used by the program PLSIMUL (described in a subsequent article) to compute the corresponding quantized levels to be compared with experimental 4 K photoluminescence data.

  5. Substrate-supported large-band-gap quantum spin Hall insulator based on III-V bismuth layers (United States)

    Padilha, J. E.; Janotti, A.; Fazzio, A.; da Silva, A. J. R.


    We show that III-V bismuth-based two-dimensional (2D) materials grown on an anion-terminated SrTe (111) substrate are 2D topological insulators. The III-Bi layers exhibit large nontrivial band gaps, ranging from 0.15 to 0.72 eV, depending on the passivation on the top surface, i.e., using hydrogen or halogens. We find that Γ -centered Dirac helical states, protected by time-reversal symmetry, appear at the edges of nanoribbon structures made of III-Bi layers on the SrTe substrate. The nontrivial character of the band gap is also determined by calculations of the Z2 invariant. We also find that the topological phase is maintained in the ultrathin quantum well heterostructures SrTe/III-Bi/SrTe, i.e., when the 2D materials are sandwiched between SrTe along the [111] direction, opening a new route for the fabrication of nanostructured devices based on 2D quantum spin Hall insulators.

  6. Techno-Economic Analysis of Three Different Substrate Removal and Reuse Strategies for III-V Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Ward, J. Scott; Remo, Timothy; Horowitz, Kelsey; Woodhouse, Michael; Sopori, Bhushan; VanSant, Kaitlyn; Basore, Paul


    The high cost of wafers suitable for epitaxial deposition of III-V solar cells has been a primary barrier to widespread use of these cells in low-concentration and one-sun terrestrial solar applications. A possible solution is to reuse the substrate many times, thus spreading its cost across many cells. We performed a bottom-up techno-economic analysis of three different strategies for substrate reuse in high-volume manufacturing: epitaxial lift-off, spalling, and the use of a porous germanium release layer. The analysis shows that the potential cost reduction resulting from substrate reuse is limited in all three strategies--not by the number of reuse cycles achievable, but by the costs that are incurred in each cycle to prepare the substrate for another epitaxial deposition. The dominant substrate-preparation cost component is different for each of the three strategies, and the cost-ranking of these strategies is subject to change if future developments substantially reduce the cost of epitaxial deposition.

  7. Towards optical hyperdoping of binary oxide semiconductors (United States)

    Schneider, A.; Sebald, K.; Dev, A.; Frank, K.; Rosenauer, A.; Voss, T.


    Surface structuring with ultrashort laser pulses is of high interest as a scalable doping technique as well as for surface nanostructuring applications. By depositing a layer of antimony before the irradiation of ZnO, we were able to incorporate a large quantity of Sb atoms into the single crystalline region of the laser modified surface for potential p-type doping. We have studied the incorporation of antimony and the material properties of laser-induced periodic surface structures (LIPSS) on c-plane ZnO upon femtosecond laser processing at two different peak fluences. We observe high spatial frequency LIPSS with structure periods from 200-370 nm and low spatial frequency LIPSS with periods of 600-700 nm. At a fluence of 0.8 J/cm2, close the ablation threshold of ZnO, the LIPSS are single crystalline except for a few nanometers of amorphous material. At a peak laser fluence of 3.1 J/cm2, they consist of polycrystalline and single crystalline ZnO areas. However, the polycrystalline part dominates with a thickness of about 500 nm.

  8. Semiconductor spintronics

    CERN Document Server

    Xia, Jianbai; Chang, Kai


    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.

  9. Movable high Q nanoresonators realized by semiconductor nanowires on a Si photonic crystal platform

    CERN Document Server

    Birowosuto, M D; Zhang, G; Tateno, K; Kuramochi, E; Taniyama, H; Takiguchi, M; Notomi, M


    Subwavelength semiconductor nanowires have recently attracted interest for photonic applications because they possess various unique optical properties and offer great potential for miniaturizing devices. However, realizing tight light confinement or efficient coupling with photonic circuits is not straightforward and remains a challenge. Here we show that a high Q nanocavity can be created by placing a single III/V semiconductor nanowire with a diameter of under 100 nm in a grooved waveguide in a Si photonic crystal, by means of nanoprobe manipulation. We observe very fast spontaneous emission (91 ps) from nanowires accelerated by the strong Purcell enhancement in nanocavities, which proves that very strong light confinement can be achieved. Furthermore, this system enables us to move the nanocavity anywhere along the waveguide. This configuration provides a significant degree of flexibility in integrated photonics and permits the addition and displacement of various functionalities of III/V nanocavity devic...

  10. Three-Phonon Phase Space as an Indicator of the Lattice Thermal Conductivity in Semiconductors (United States)

    Lindsay, L.; Broido, D. A.


    The room temperature lattice thermal conductivity of many semiconductors is limited primarily by three-phonon scattering processes arising from the anharmonicity of the interatomic potential. We employ an adiabatic bond charge model [1,2] for the phonon dispersions to calculate the phase space for three-phonon scattering events of several group IV and III-V semiconductors. We find that the amount of phase space available for this scattering in materials varies inversely with their measured thermal conductivities. Anomalous behavior occurs in III-V materials having large mass differences between cation and anion, which we explain in terms of the severely restricted three-phonon phase space arising from the large gap between acoustic and optic phonon branches. [1] W. Weber, Physical Review B 15, 4789 (1977). [2] K. C. Rustagi and W. Weber, Solid State Communications 18, 673 (1976).

  11. Passivation of electrically active centers by Hydrogen and Lithium in Semiconductors

    CERN Multimedia


    The hyperfine technique of Perturbed Angular Correlation Spectroscopy (PAC) has proven to be excellently suited for the microscopic investigation of impurity complexes in semiconductors. But this method is seriously limited by the small number of chemically different isotopes which are suitable for PAC measurements and represent electrically active centers in semiconductors. This bottleneck can be widely overcome by the ISOLDE facility which provides a great variety of shortliving PAC isotopes. The probe atom $^{111m}$Cd, provided by ISOLDE opened the first successful access to PAC investigations of III-V compounds and enabled also the first PAC experiments on double acceptors in silicon and germamum. \\\\ \\\\ At the new ISOLDE facility our experiments were concentrated on the passivation of electrically active centres by hydrogen and lithium in Si, Ge and III-V compounds. Experiments on $^{111m}$Cd in Ge revealed the formation of two different acceptor hydrogen and two different acceptor lithium complexes respe...

  12. Semiconductor heterojunctions

    CERN Document Server

    Sharma, B L


    Semiconductor Heterojunctions investigates various aspects of semiconductor heterojunctions. Topics covered include the theory of heterojunctions and their energy band profiles, electrical and optoelectronic properties, and methods of preparation. A number of heterojunction devices are also considered, from photovoltaic converters to photodiodes, transistors, and injection lasers.Comprised of eight chapters, this volume begins with an overview of the theory of heterojunctions and a discussion on abrupt isotype and anisotype heterojunctions, along with graded heterojunctions. The reader is then

  13. Analytic Franz-Keldysh effect in one-dimensional polar semiconductors

    CERN Document Server

    Pedersen, T G


    The optical properties of a one-dimensional polar semiconductor in a strong electric field are considered. This class of materials includes non-centrosymmetric III-V inorganic quantum wires but also polar conjugated polymers such as polymethineimine. The polar Franz-Keldysh effect is derived via an analytic expression for the complex dielectric constant including line broadening and linear field terms. Results for the high-field non-perturbative regime as well as the low-field expansion are presented.

  14. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    Energy Technology Data Exchange (ETDEWEB)

    Russell Dupuis


    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers whole years of the three-year program 'Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications'. The research activities were focused on the development of p-type layer that has less/no detrimental thermal annealing effect on as well as excellent structural and electrical properties and the development of green LED active region that has superior luminescence quality for {lambda}{approx}540nm green LEDs. We have also studied (1) the thermal annealing effect on blue and green LED active region during the p-type layer growth; (2) the effect of growth parameters and structural factors for LED active region on electroluminescence properties; (3) the effect of substrates and orientation on electrical and electro-optical properties of green LEDs. As a progress highlight, we obtained green-LED-active-region-friendly In{sub 0.04}Ga{sub 0.96}N:Mg exhibiting low resistivity with higher hole concentration (p=2.0 x 10{sup 18} cm{sup -3} and a low resistivity of 0.5 {omega}-cm) and improved optical quality green LED active region emitting at {approx}540nm by electroluminescence. The LEDs with p-InGaN layer can act as a quantum-confined Stark effect mitigation layer by reducing strain in the QW. We also have achieved (projected) peak IQE of {approx}25% at {lambda}{approx}530 nm and of {approx}13% at {lambda}{approx}545 nm. Visible LEDs on a non-polar substrate using (11-20) {alpha}-plane bulk substrates. The absence of quantum-confined Stark effect was confirmed but further improvement in electrical and optical properties is required.

  15. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    Energy Technology Data Exchange (ETDEWEB)

    Russell D. Dupuis


    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers the first year of the three-year program ''Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications''. The first year activities were focused on the installation, set-up, and use of advanced equipment for the metalorganic chemical vapor deposition growth of III-nitride films and the characterization of these materials (Task 1) and the design, fabrication, testing of nitride LEDs (Task 4). As a progress highlight, we obtained improved quality of {approx} 2 {micro}m-thick GaN layers (as measured by the full width at half maximum of the asymmetric (102) X-ray diffraction peak of less than 350 arc-s) and higher p-GaN:Mg doping level (free hole carrier higher than 1E18 cm{sup -3}). Also in this year, we have developed the growth of InGaN/GaN active layers for long-wavelength green light emitting diodes, specifically, for emission at {lambda} {approx} 540nm. The effect of the Column III precursor (for Ga) and the post-growth thermal annealing effect were also studied. Our LED device fabrication process was developed and initially optimized, especially for low-resistance ohmic contacts for p-GaN:Mg layers, and blue-green light emitting diode structures were processed and characterized.

  16. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    Energy Technology Data Exchange (ETDEWEB)

    Russell D. Dupuis


    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers the second year of the three-year program ''Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications''. The second year activities were focused on the development of p-type layer that has less/no detrimental thermal annealing effect on green LED active region as well as excellent structural and electrical properties and the development of green LED active region that has superior luminescence quality for {lambda} {approx}540nm green LEDs. We have also studied the thermal annealing effect on blue and green LED active region during the p-type layer growth. As a progress highlight, we obtained green-LED-active-region-friendly In{sub 0.04}Ga{sub 0.96}N:Mg exhibiting low resistivity with higher hole concentration (p=2.0 x 10{sup 18} cm{sup -3} and a low resistivity of 0.5 {Omega}-cm) and improved optical quality green LED active region emitting at {lambda} {approx}540nm by electroluminescence. The active region of the green LEDs was found to be much more sensitive to the thermal annealing effect during the p-type layer growth than that of the blue LEDs. We have designed grown, fabricated green LED structures for both 520 nm and 540 nm for the evaluation of second year green LED development.

  17. Influence of light waves on the thermoelectric power under large magnetic field in III-V, ternary and quaternary materials

    Energy Technology Data Exchange (ETDEWEB)

    Ghatak, K.P. [Department of Electronic Science, The University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Bhattacharya, S. [Post Graduate Department of Computer Science, St. Xavier' s College, 30 Park Street, Kolkata 700 016 (India); Pahari, S. [Department of Administration, Jadavpur University, Kolkata 700 032 (India); De, D. [Department of Computer Science and Engineering, West Bengal University of Technology, B. F. 142, Sector I, Salt Lake, Kolkata 700 064 (India); Ghosh, S.; Mitra, M. [Department of Electronics and Telecommunication Engineering, Bengal Engineering and Science University, Howrah 711 103 (India)


    We study theoretically the influence of light waves on the thermoelectric power under large magnetic field (TPM) for III-V, ternary and quaternary materials, whose unperturbed energy-band structures, are defined by the three-band model of Kane. The solution of the Boltzmann transport equation on the basis of this newly formulated electron dispersion law will introduce new physical ideas and experimental findings in the presence of external photoexcitation. It has been found by taking n-InAs, n-InSb, n-Hg{sub 1-x}Cd{sub x}Te and n-In{sub 1-x}Ga{sub x}As{sub y}P{sub 1-y} lattice matched to InP as examples that the TPM decreases with increase in electron concentration, and increases with increase in intensity and wavelength, respectively in various manners. The strong dependence of the TPM on both light intensity and wavelength reflects the direct signature of light waves that is in direct contrast as compared with the corresponding bulk specimens of the said materials in the absence of external photoexcitation. The rate of change is totally band-structure dependent and is significantly influenced by the presence of the different energy-band constants. The well-known result for the TPM for nondegenerate wide-gap materials in the absence of light waves has been obtained as a special case of the present analysis under certain limiting conditions and this compatibility is the indirect test of our generalized formalism. Besides, we have also suggested the experimental methods of determining the Einstein relation for the diffusivity:mobility ratio, the Debye screening length and the electronic contribution to the elastic constants for materials having arbitrary dispersion laws. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  18. Interacting binaries

    CERN Document Server

    Shore, S N; van den Heuvel, EPJ


    This volume contains lecture notes presented at the 22nd Advanced Course of the Swiss Society for Astrophysics and Astronomy. The contributors deal with symbiotic stars, cataclysmic variables, massive binaries and X-ray binaries, in an attempt to provide a better understanding of stellar evolution.

  19. EDITORIAL: The 21st Nordic Semiconductor Meeting (United States)


    This Topical Issue contains works presented at the 21st Nordic Semiconductor Meeting (21NSM) held at Sundvolden, Norway, 18-19 August 2005. The institutions supporting 21NSM were: University of Oslo, SINTEF, the Norwegian Defense Research Establishment and Vestfold University College. The Nordic Semiconductor Meeting has become an international forum that has been held every other year in a relay fashion in Denmark, Finland, Iceland, Norway and Sweden. The focus of the meeting has been on original research and science being carried out on semiconductor materials, devices and systems. Reports on industrial activity have usually been featured at the meetings. The topics have ranged from fundamental research on point defects in a semiconductor to system architecture of semiconductor electronic devices. For the last five meetings the proceedings have been printed in a dedicated volume of Physica Scripta in the Topical Issue series. 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 expected high standards of the series. The range of topics covered by this volume is broad, reflecting the call for papers; most of the papers have an element of materials science and the largest portion of these deal with other semiconductor materials other than silicon. The 21NSM was supported by the following sponsors: Renewable Energy Corporation (REC), EMF III-V Innovations (EMF), and the Nordic Research Board (NordForsk). Terje G Finstad Department of Physics, University of Oslo, Norway Andrej Y Kuznetsov and Bengt G Svensson Centre for Materials Science and Nanotechnology, University of Oslo, Norway

  20. Tailoring spin-orbit torque in diluted magnetic semiconductors

    KAUST Repository

    Li, Hang


    We study the spin orbit torque arising from an intrinsic linear Dresselhaus spin-orbit coupling in a single layer III-V diluted magnetic semiconductor. We investigate the transport properties and spin torque using the linear response theory, and we report here: (1) a strong correlation exists between the angular dependence of the torque and the anisotropy of the Fermi surface; (2) the spin orbit torque depends nonlinearly on the exchange coupling. Our findings suggest the possibility to tailor the spin orbit torque magnitude and angular dependence by structural design.

  1. A Semiconductor Under Insulator Technology in Indium Phosphide

    CERN Document Server

    Mnaymneh, Khaled; Frédérick, Simon; Lapointe, Jean; Poole, Philip J; Williams, Robin L


    This Letter introduces a Semiconductor-Under-Insulator (SUI) technology in InP for designing strip waveguides that interface InP photonic crystal membrane structures. Strip waveguides in InP-SUI are supported under an atomic layer deposited insulator layer in contrast to strip waveguides in silicon supported on insulator. We show a substantial improvement in optical transmission when using InP-SUI strip waveguides interfaced with localized photonic crystal membrane structures when compared with extended photonic crystal waveguide membranes. Furthermore, SUI makes available various fiber-coupling techniques used in SOI, such as sub-micron coupling, for planar membrane III-V systems.

  2. Increased bismuth concentration in MBE GaAs{sub 1−x}Bi{sub x} films by oscillating III/V flux ratio during growth

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Adam W., E-mail:; Babcock, Susan E. [Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706 (United States); Li, Jincheng; Brown, April S. [Electrical and Computer Engineering, Duke University, Durham, North Carolina 27707 (United States)


    The authors have examined bismuth concentration profiles in GaAs{sub 1−x}Bi{sub x} films grown by molecular beam epitaxy using high angle annular dark field imaging (Z-contrast imaging) in an aberration-corrected scanning transmission electron microscope in conjunction with x-ray diffraction. Samples were grown with a gradient in each of the component fluxes, and therefore, the III/V ratio across the substrate. Rotating the sample during growth exposed the growth surface to an oscillating III/V flux ratio. Sinusoidal [Bi] profiles resulted in the growth direction, the wavelength and number of which were consistent with the growth rate and the rate of substrate rotation. However, the magnitude of [Bi] in the observed fluctuations was greater than the maximum [Bi] achieved using the same Bi flux and Ga/As flux ratios in steady-state conditions on a stationary substrate, suggesting that varying the III/V flux ratio during growth promotes the incorporation of Bi in GaAs{sub 1−x}Bi{sub x} films. A proposed qualitative model for how this enhancement might occur hypothesizes a critical role for alternating growth and shrinkage of Ga-Bi predroplet clusters on the surface as the growing material is rotated through Ga-rich and As-rich flux compositions.

  3. Semiconductor statistics

    CERN Document Server

    Blakemore, J S


    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

  4. Oxide semiconductors

    CERN Document Server

    Svensson, Bengt G; Jagadish, Chennupati


    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

  5. Analytical solutions for elastic binary nanotubes of arbitrary chirality (United States)

    Jiang, Lai; Guo, Wanlin


    Analytical solutions for the elastic properties of a variety of binary nanotubes with arbitrary chirality are obtained through the study of systematic molecular mechanics. This molecular mechanics model is first extended to chiral binary nanotubes by introducing an additional out-of-plane inversion term into the so-called stick-spiral model, which results from the polar bonds and the buckling of binary graphitic crystals. The closed-form expressions for the longitudinal and circumferential Young's modulus and Poisson's ratio of chiral binary nanotubes are derived as functions of the tube diameter. The obtained inversion force constants are negative for all types of binary nanotubes, and the predicted tube stiffness is lower than that by the former stick-spiral model without consideration of the inversion term, reflecting the softening effect of the buckling on the elastic properties of binary nanotubes. The obtained properties are shown to be comparable to available density functional theory calculated results and to be chirality and size sensitive. The developed model and explicit solutions provide a systematic understanding of the mechanical performance of binary nanotubes consisting of III-V and II-VI group elements.

  6. Analytical solutions for elastic binary nanotubes of arbitrary chirality (United States)

    Jiang, Lai; Guo, Wanlin


    Analytical solutions for the elastic properties of a variety of binary nanotubes with arbitrary chirality are obtained through the study of systematic molecular mechanics. This molecular mechanics model is first extended to chiral binary nanotubes by introducing an additional out-of-plane inversion term into the so-called stick-spiral model, which results from the polar bonds and the buckling of binary graphitic crystals. The closed-form expressions for the longitudinal and circumferential Young's modulus and Poisson's ratio of chiral binary nanotubes are derived as functions of the tube diameter. The obtained inversion force constants are negative for all types of binary nanotubes, and the predicted tube stiffness is lower than that by the former stick-spiral model without consideration of the inversion term, reflecting the softening effect of the buckling on the elastic properties of binary nanotubes. The obtained properties are shown to be comparable to available density functional theory calculated results and to be chirality and size sensitive. The developed model and explicit solutions provide a systematic understanding of the mechanical performance of binary nanotubes consisting of III-V and II-VI group elements.

  7. Semiconductor Detectors; Detectores de Semiconductores

    Energy Technology Data Exchange (ETDEWEB)

    Cortina, E.


    Particle detectors based on semiconductor materials are among the few devices used for particle detection that are available to the public at large. In fact we are surrounded by them in our daily lives: they are used in photoelectric cells for opening doors, in digital photographic and video camera, and in bar code readers at supermarket cash registers. (Author)

  8. Shadow mask assisted heteroepitaxy of compound semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Schallenberg, T.


    Shadow Mask assisted Molecular Beam Epitaxy (SMMBE) is a technique enabling selected area epitaxy of semiconductor heterostructures through shadow masks. The objective of this work was the development of the SMMBE technique for the reliable fabrication of compound semiconductor nanostructures of high structural and optical quality. In order to accomplish this, technological processes have been developed and optimized. One of the technological developments to this effect, which has substantially enhanced the versatility of SMMBE, is the introduction of a new type of freestanding shadow masks. A consistent model has been developed, which successfully explains the growth dynamics of molecular beam epitaxy through shadow masks. The predictions of the model regarding the growth of II-VI and III-V compounds have been tested experimentally and the dependence of the growth rates on the growth parameters has been verified. Moreover, it has been shown, that selected area epitaxy of II-VI and III-V compounds are governed by different surface kinetics. In addition to the basic surface kinetic processes described by the model, the roles of orientation and strain-dependent growth dynamics, partial shadow, and material deposition on the mask (closure of apertures) have been discussed. The resulting advanced understanding of the growth dynamics (model and basic experiments) in combination with the implementation of technical improvements has enabled the development and application of a number of different processes for the fabrication of both II-VI and III-V nanostructures. In addition to specific material properties, various other phenomena have been exploited, e.g., self-organization. Bright cathodoluminescence demonstrates that the resulting quantum structures are of high structural and optical quality. In addition to these results the limitations of the method have also been discussed, and various approaches to overcome them have been suggested. Moreover, propositions for the

  9. High-performance GaAs metal-insulator-semiconductor field-effect transistors enabled by self-assembled nanodielectrics (United States)

    Lin, H. C.; Ye, P. D.; Xuan, Y.; Lu, G.; Facchetti, A.; Marks, T. J.


    High-performance GaAs metal-insulator-semiconductor field-effect-transistors (MISFETs) fabricated with very thin self-assembled organic nanodielectrics (SANDs), deposited from solution at room temperature, are demonstrated. A submicron gate-length depletion-mode n-channel GaAs MISFET with SAND thicknesses ranging from 5.5to16.5nm exhibit a gate leakage current density <10-5A/cm2 at a gate bias smaller than 3V, a maximum drain current of 370mA/mm at a forward gate bias of 2V, and a maximum intrinsic transconductance of 170mS/mm. The importance of appropriate GaAs surface chemistry treatments on SAND/GaAs interface properties is also presented. Application of SANDs to III-V compound semiconductors affords more opportunities to manipulate the complex III-V surface chemistry with broad materials options.

  10. A Model of Numerical Calculation of Conductivity for III-V MBE Epilayers Using a Hall Device

    Directory of Open Access Journals (Sweden)

    Andrzej Wolkenberg


    Full Text Available An electrical conduction versus temperature model using a Hall device was developed. In the case of InAs, InGaAs, and GaAs MBE epilayers, the prediction agrees well with the experimental results. Herein, we explain here how these calculated fractions of total conductivity describe the measured values. The method allows for the calculation of the carrier concentration and mobility of each component of a multicarrier system. The extracted concentrations are used to characterise the different components of charge transport in the active layer. The conductance values G [S] of these components of charge transport were obtained. Also the scattering events for the investigated samples are presented. The analysis of the experimental results for three semiconductor compositions and different concentrations demonstrates the utility of our method in comparing the conductance of each component of the multilayered system as a function of temperature.

  11. Semiconductor Optics

    CERN Document Server

    Klingshirn, Claus F


    This updated and enlarged new edition of Semiconductor Optics provides an introduction to and an overview of semiconductor optics from the IR through the visible to the UV, including linear and nonlinear optical properties, dynamics, magneto and electrooptics, high-excitation effects and laser processes, some applications, experimental techniques and group theory. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered extend from physics to materials science and optoelectronics. Significantly updated chapters add coverage of current topics such as electron hole plasma, Bose condensation of excitons and meta materials. Over 120 problems, chapter introductions and a detailed index make it the key textbook for graduate students in physics. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered ...

  12. Semiconductor sensors

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, Frank, E-mail: frank.hartmann@cern.c [Institut fuer Experimentelle Kernphysik, KIT, Wolfgang-Gaede-Str. 1, Karlsruhe 76131 (Germany)


    Semiconductor sensors have been around since the 1950s and today, every high energy physics experiment has one in its repertoire. In Lepton as well as Hadron colliders, silicon vertex and tracking detectors led to the most amazing physics and will continue doing so in the future. This contribution tries to depict the history of these devices exemplarily without being able to honor all important developments and installations. The current understanding of radiation damage mechanisms and recent R and D topics demonstrating the future challenges and possible technical solutions for the SLHC detectors are presented. Consequently semiconductor sensor candidates for an LHC upgrade and a future linear collider are also briefly introduced. The work presented here is a collage of the work of many individual silicon experts spread over several collaborations across the world.

  13. Nuclear Electrical and Optical Studies of Hydrogen in Semiconductors.

    CERN Multimedia

    Dietrich, M; Toulemonde, M


    During the last years, the understanding of H and its interaction with dopant atoms in Si, Ge and III-V semiconductors has improved considerably concerning the stability of the formed complexes their structural arrangements, and the implications of this interaction on the electrical properties of the semiconductors " passivation " The perturbed angular correlation technique (PAC) has contributed to the understanding of this phenomena on an atomistic scale using radioactive isotopes provided by ISOLDE. \\\\ \\\\The aim of the proposed experiments is twofold: \\\\ \\\\\\begin{enumerate} \\item The H passivation mechanism of acceptors in GaN and ternary III-V compounds (AlGaAs, GaInP, AlGaN) shall be investigated, using the PAC probe atom $^{111m}$Cd as a 'representative' of group II-B metal acceptors. The problems addressed in these technological important systems are microscopic structure, formation and stability of the hydrogen correlated complexes as function of doping and stoichiometry (i.e. the size of the band gap)...

  14. Building a spin quantum bit register using semiconductor nanowires. (United States)

    Baugh, J; Fung, J S; Mracek, J; LaPierre, R R


    This paper reviews recent advances in engineering spin quantum bits (qubits) in semiconductor quantum dots and describes an approach based on top-gated semiconductor nanowire devices. Fast electrical single-spin manipulation is achievable, in principle, using the spin-orbit interaction intrinsic to III-V materials, such as InAs, in concert with AC electric fields. Combined with sub-nanosecond gate control of the nearest-neighbor exchange interaction and spin readout by spin-to-charge conversion, a fully electrical solid-state quantum processor is within reach. We outline strategies for spin manipulation, robust readout and mitigation of decoherence due to nuclear fields that, when combined in a single device, should give a viable multi-qubit testbed and a building block for larger scale quantum devices.

  15. Microscopical Studies of Structural and Electronic Properties of Semiconductors

    CERN Multimedia


    The electronic and structural properties of point defects in semiconductors, e.g. radiation defects, impurities or passivating defects can excellently be studied by the hyperfine technique of Perturbed Angular Correlation (PAC). The serious limitation of this method, the small number of chemically different radioactive PAC probe atoms can be widely overcome by means of ISOLDE. Providing shortliving isotopes, which represent common dopants as well as suitable PAC probe atoms, the ISOLDE facility enables a much broader application of PAC to problems in semiconductor physics.\\\\ Using the probe atom $^{111m}$ Cd , the whole class of III-V compounds becomes accessible for PAC investigations. First successful experiments in GaAs, InP and GaP have been performed, concerning impurity complex formation and plasma induced defects. In Si and Ge, the electronic properties~-~especially their influence on acceptor-donor interaction~-~could be exemplarily st...

  16. Materials and Reliability Handbook for Semiconductor Optical and Electron Devices

    CERN Document Server

    Pearton, Stephen


    Materials and Reliability Handbook for Semiconductor Optical and Electron Devices provides comprehensive coverage of reliability procedures and approaches for electron and photonic devices. These include lasers and high speed electronics used in cell phones, satellites, data transmission systems and displays. Lifetime predictions for compound semiconductor devices are notoriously inaccurate due to the absence of standard protocols. Manufacturers have relied on extrapolation back to room temperature of accelerated testing at elevated temperature. This technique fails for scaled, high current density devices. Device failure is driven by electric field or current mechanisms or low activation energy processes that are masked by other mechanisms at high temperature. The Handbook addresses reliability engineering for III-V devices, including materials and electrical characterization, reliability testing, and electronic characterization. These are used to develop new simulation technologies for device operation and ...

  17. Arsenic (III, V), indium (III), and gallium (III) toxicity to zebrafish embryos using a high-throughput multi-endpoint in vivo developmental and behavioral assay. (United States)

    Olivares, Christopher I; Field, Jim A; Simonich, Michael; Tanguay, Robert L; Sierra-Alvarez, Reyes


    Gallium arsenide (GaAs), indium gallium arsenide (InGaAs) and other III/V materials are finding increasing application in microelectronic components. The rising demand for III/V-based products is leading to increasing generation of effluents containing ionic species of gallium, indium, and arsenic. The ecotoxicological hazard potential of these streams is unknown. While the toxicology of arsenic is comprehensive, much less is known about the effects of In(III) and Ga(III). The embryonic zebrafish was evaluated for mortality, developmental abnormalities, and photomotor response (PMR) behavior changes associated with exposure to As(III), As(V), Ga(III), and In(III). The As(III) lowest observable effect level (LOEL) for mortality was 500 μM at 24 and 120 h post fertilization (hpf). As(V) exposure was associated with significant mortality at 63 μM. The Ga(III)-citrate LOEL was 113 μM at 24 and 120 hpf. There was no association of significant mortality over the tested range of In(III)-citrate (56-900 μM) or sodium citrate (213-3400 μM) exposures. Only As(V) resulted in significant developmental abnormalities with LOEL of 500 μM. Removal of the chorion prior to As(III) and As(V) exposure was associated with increased incidence of mortality and developmental abnormality suggesting that the chorion may normally attenuate mass uptake of these metals by the embryo. Finally, As(III), As(V), and In(III) caused PMR hypoactivity (49-69% of control PMR) at 900-1000 μM. Overall, our results represent the first characterization of multidimensional toxicity effects of III/V ions in zebrafish embryos helping to fill a significant knowledge gap, particularly in Ga(III) and In(III) toxicology.

  18. Oxide-Free Bonding of III-V-Based Material on Silicon and Nano-Structuration of the Hybrid Waveguide for Advanced Optical Functions

    Directory of Open Access Journals (Sweden)

    Konstantinos Pantzas


    Full Text Available Oxide-free bonding of III-V-based materials for integrated optics is demonstrated on both planar Silicon (Si surfaces and nanostructured ones, using Silicon on Isolator (SOI or Si substrates. The hybrid interface is characterized electrically and mechanically. A hybrid InP-on-SOI waveguide, including a bi-periodic nano structuration of the silicon guiding layer is demonstrated to provide wavelength selective transmission. Such an oxide-free interface associated with the nanostructured design of the guiding geometry has great potential for both electrical and optical operation of improved hybrid devices.

  19. Croissance hétérogène de semi-conducteurs III-V sur silicium : vers l'optoélectronique sur silicium


    Cornet, Charles; Létoublon, Antoine; Guo, Weiming; Bondi, Alexandre; Richard, Soline; Rohel, Tony; Chevalier, Nicolas; Dehaese, Olivier; Tavernier, Karine; Perrin, Mathieu,; Jancu, Jean-Marc; Durand, Olivier; Bertru, Nicolas; Even, Jacky; Loualiche, Slimane


    National audience; L’intérêt d’une croissance hétérogène cohérente et monolithique de semiconducteurs III-V sur substrat de silicium est exposée au regard des composants optoélectroniques visés. Les derniers développements sur la croissance cohérente de GaP sur silicium, et des possibles émetteurs optiques seront présentés.

  20. Semiconductor laser

    Energy Technology Data Exchange (ETDEWEB)

    Ito, K.; Shyuue, M.


    A distributed feedback semiconductor laser is proposed which generates several beams with equal wavelengths in different directions. For this purpose, 1 millimeter grooves are cut into the surface of an n-type conductance GaAs plate in three different directions; these grooves form a diffraction grating. The center of this plate has no grooves and is bombarded by an He/Ne laser beam. The diffraction gratings provide resonance properties and generate laser beams with wavelengths of 8850, 9000 and 9200 angstroms.

  1. Microscopic Optical Characterization of Free Standing III-Nitride Substrates, ZnO Bulk Crystals, and III-V Structures for Non-Linear Optics. Part 2 (United States)


    Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39-18 GIR: Materiales semiconductores y nanoestructuras para la optoelectró la Materia Condensada Edificio de i+d Paseo de Belen 1 47011 Valladolid, Spain GIR: Materiales semiconductores y nanoestructuras para la...380 400 420 440 460 480 500 520 540 560 580 600 620 nm 1 2 3 2 3 1 GIR: Materiales semiconductores y

  2. Power semiconductors

    CERN Document Server

    Kubát, M


    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...

  3. Magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bihler, Christoph


    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.)

  4. Semiconductor Laser Measurements Laboratory (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. Desktop setup for binary holograms (United States)

    Ginter, Olaf; Rothe, Hendrik


    Binary gratings as holograms itself or as photographic masking tools for further fabrication steps can fulfill a lot of applications. The commonly used semiconductor technologies for direct writing of high resolution structures are often too expensive. On the other hand computer plots at a reasonable price with photographic reduction do not meet the needs of precision e.g. for interferometric inspection. The lack of cheap and reliable instruments for direct writing in an appropriate resolution is still a problem in fabricating synthetic holograms. Using off-the-shelf components a direct writing plotter for binary patterns can be built at moderate costs. Typical design rules as well as experimental results are given and the final setup is introduced.

  6. Solution-processed semiconductors for next-generation photodetectors (United States)

    García de Arquer, F. Pelayo; Armin, Ardalan; Meredith, Paul; Sargent, Edward H.


    Efficient light detection is central to modern science and technology. Current photodetectors mainly use photodiodes based on crystalline inorganic elemental semiconductors, such as silicon, or compounds such as III-V semiconductors. Photodetectors made of solution-processed semiconductors — which include organic materials, metal-halide perovskites and quantum dots — have recently emerged as candidates for next-generation light sensing. They combine ease of processing, tailorable optoelectronic properties, facile integration with complementary metal-oxide-semiconductors, compatibility with flexible substrates and good performance. Here, we review the recent advances and the open challenges in the field of solution-processed photodetectors, examining the topic from both the materials and the device perspective and highlighting the potential of the synergistic combination of materials and device engineering. We explore hybrid phototransistors and their potential to overcome trade-offs in noise, gain and speed, as well as the rapid advances in metal-halide perovskite photodiodes and their recent application in narrowband filterless photodetection.

  7. Estimation of Bi induced changes in the direct E0 band gap of III-V-Bi alloys and comparison with experimental data (United States)

    Samajdar, D. P.; Dhar, S.


    Quantum dielectric Theory (QDT) is used to explain the band gap bowing effect observed in III-V-Bismides such as InSb1-xBix, InAs1-xBix, InP1-xBix, GaSb1-xBix, GaAs1-xBix and GaP1-xBix. The dependence of the direct E0 band gap for these alloys on Bi mole fraction is calculated using QDT which requires the evaluation of the bowing parameter c. The bowing parameter gives the deviation of the direct E0 band gap from the linear relationship of E0 with Bi mole fraction. The band gap reduction values obtained using QDT are compared with those calculated using Virtual Crystal approximation (VCA) and Valence Band Anticrossing (VBAC) model as well as with the reported experimental data and the results of the comparison shows excellent agreement.

  8. Progress and Continuing Challenges in GaSb-based III-V Alloys and Heterostructures Grown by Organometallic Vapor Phase Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    CA Wang


    This paper discusses progress in the preparation of mid-IR GaSb-based III-V materials grown by organometallic vapor phase epitaxy (OMVPE). The growth of these materials is complex, and fundamental and practical issues associated with their growth are outlined. Approaches that have been explored to further improve the properties and performance are briefly reviewed. Recent materials and device results on GaInAsSb bulk layers and GaInAsSb/AlGaAsSb heterostructures, grown lattice matched to GaSb, are presented. State-of-the-art GaInAsSb materials and thermophotovoltaic devices have been achieved. This progress establishes the high potential of OMVPE for mid-IR GaSb-based devices.

  9. Benchmarks of a III-V TFET technology platform against the 10-nm CMOS FinFET technology node considering basic arithmetic circuits (United States)

    Strangio, S.; Palestri, P.; Lanuzza, M.; Esseni, D.; Crupi, F.; Selmi, L.


    In this work, a benchmark for low-power digital applications of a III-V TFET technology platform against a conventional CMOS FinFET technology node is proposed. The analysis focuses on full-adder circuits, which are commonly identified as representative of the digital logic environment. 28T and 24T topologies, implemented in complementary-logic and transmission-gate logic, respectively, are investigated. Transient simulations are performed with a purpose-built test-bench on each single-bit full adder solution. The extracted delays and energy characteristics are post-processed and translated into figures-of-merit for multi-bit ripple-carry-adders. Trends related to the different full-adder implementations (for the same device technology platform) and to the different technology platforms (for the same full-adder topology) are presented and discussed.

  10. Effects of brining on the corrosion of ZVI and its subsequent As(III/V) and Se(IV/VI) removal from water. (United States)

    Yang, Zhe; Xu, Hui; Shan, Chao; Jiang, Zhao; Pan, Bingcai


    Zero-valent iron (ZVI) has been extensively applied in water remediation, and most of the ZVI materials employed in practical applications are iron scraps, which have usually been corroded to certain extent under different conditions. In this study, the effects of brining with six solutions (NaCl, Na2SO4, NaHCO3, Na2SiO3, NH4Cl, and NaH2PO4) on the corrosion of ZVI and its performance in the removal of As(III/V)/Se(IV/VI) were systematically investigated. All the studied solutions enhanced the corrosion of ZVI except for Na2SiO3, and the degrees of corrosion followed the order of NH4Cl > NaH2PO4 > Na2SO4 > NaCl > NaHCO3 > H2O > Na2SiO3. The corrosion products derived from ZVI were identified by SEM and XRD, and the dominant corrosion products varied with the type of brine solution. The positive correlation between the degree of ZVI corrosion and As(III/V)/Se(IV/VI) removal by the pre-corroded ZVI (pcZVI) was verified. In addition, As and Se removal by pcZVI was realized via a comprehensive process including adsorption and reduction, as further supported by the XPS analysis. We believe this study will shed new light upon the selection of iron materials pre-corroded under different saline conditions for practical water remediation.

  11. Semiconductor laser. Halbleiterlaser

    Energy Technology Data Exchange (ETDEWEB)

    Wuenstel, K.; Gohla, B.; Tegude, F.; Luz, G.; Hildebrand, O.


    A highly modulable semiconductor laser and a process for its manufacture are described. The semiconductor laser has a substrate, a stack of semiconductor layers and electrical contacts. To reduce the capacity, the width of the stack of semiconductor layers is reduced at the sides by anisotropic etching. The electrical contacts are situated on the same side of the substrate and are applied in the same stage of the process. The semiconductor laser is suitable for monolithic integration in other components.

  12. A review of thermal processing in the subsecond range: semiconductors and beyond (United States)

    Rebohle, Lars; Prucnal, Slawomir; Skorupa, Wolfgang


    Thermal processing in the subsecond range comprises modern, non-equilibrium annealing techniques which allow various material modifications at the surface without affecting the bulk. Flash lamp annealing (FLA) is one of the most diverse methods for short-time annealing with applications ranging from the classical field of semiconductor doping to the treatment of polymers and flexible substrates. It still continues to extend its use to other material classes and applications, and is becoming of interest for an increasing number of users. In this review we present a short, but comprehensive and consistent picture of the current state-of-the-art of FLA, sometimes also called pulsed light sintering. In the first part we take a closer look at the physical and technological background, namely the electrical and optical specifications of flash lamps, the resulting temperature profiles, and the corresponding implications for process-relevant parameters such as reproducibility and homogeneity. The second part briefly considers the various applications of FLA, starting with the classical task of defect minimization and ultra-shallow junction formation in Si, followed by further applications in Si technology, namely in the fields of hyperdoping, crystallization of thin amorphous films, and photovoltaics. Subsequent chapters cover the topics of doping and crystallization in Ge and silicon carbide, doping of III-V semiconductors, diluted magnetic semiconductors, III-V nanocluster synthesis in Si, annealing of transparent conductive oxides and high-k materials, nanoclusters in dielectric matrices, and the use of FLA for flexible substrates.

  13. Fowler-Nordheim field emission effects in semiconductor nanostructures

    CERN Document Server

    Bhattacharya, Sitangshu


    This monograph solely presents the Fowler-Nordheim field emission (FNFE) from semiconductors and their nanostructures. The materials considered are quantum confined non-linear optical, III-V, II-VI, Ge, Te, carbon nanotubes, PtSb2, stressed materials, Bismuth, GaP, Gallium Antimonide, II-V, Bi2Te3, III-V, II-VI, IV-VI and HgTe/CdTe superlattices with graded interfaces and effective mass superlattices under magnetic quantization and quantum wires of the aforementioned superlattices. The FNFE in opto-electronic materials and their quantum confined counterparts is studied in the presence of light waves and intense electric fields on the basis of newly formulated electron dispersion laws that control the studies of such quantum effect devices. The importance of band gap measurements in opto-electronic materials in the presence of external fields is discussed from this perspective. This monograph contains 200 open research problems which form the very core and are useful for Ph. D students and researchers. The boo...

  14. Fowler-Nordheim field emission. Effects in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Sitangshu [Indian Institute of Science, Bangalore (India). Nano Scale Device Research Laboratory; Ghatak, Kamakhya Prasad [Calcutta Univ. (India). Dept. of Electronics Science


    This monograph solely presents the Fowler-Nordheim field emission (FNFE) from semiconductors and their nanostructures. The materials considered are quantum confined non-linear optical, III-V, II-VI, Ge, Te, carbon nanotubes, PtSb{sub 2}, stressed materials, Bismuth, GaP, Gallium Antimonide, II-V, Bi{sub 2}Te{sub 3}, III-V, II-VI, IV-VI and HgTe/CdTe superlattices with graded interfaces and effective mass superlattices under magnetic quantization and quantum wires of the aforementioned superlattices. The FNFE in opto-electronic materials and their quantum confined counterparts is studied in the presence of light waves and intense electric fields on the basis of newly formulated electron dispersion laws that control the studies of such quantum effect devices. The importance of band gap measurements in opto-electronic materials in the presence of external fields is discussed from this perspective. This monograph contains 200 open research problems which form the very core and are useful for Ph. D students and researchers. The book can also serve as a basis for a graduate course on field emission from solids. (orig.)

  15. Binary effectivity rules

    DEFF Research Database (Denmark)

    Keiding, Hans; Peleg, Bezalel


    is binary if it is rationalized by an acyclic binary relation. The foregoing result motivates our definition of a binary effectivity rule as the effectivity rule of some binary SCR. A binary SCR is regular if it satisfies unanimity, monotonicity, and independence of infeasible alternatives. A binary...... effectivity rule is regular if it is the effectivity rule of some regular binary SCR. We characterize completely the family of regular binary effectivity rules. Quite surprisingly, intrinsically defined von Neumann-Morgenstern solutions play an important role in this characterization...

  16. Mechanisms of double magnetic exchange in dilute magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Fleurov, V. E-mail:; Kikoin, K.; Ivanov, V.A.; Krstajic, P.M.; Peeters, F.M


    A microscopic Hamiltonian for interacting manganese impurities in dilute magnetic semiconductors (DMS) is derived. It is shown that in p-type III-V DMS, the indirect exchange between Mn impurities has similarities with the Zener mechanism in transition metal oxides. Here the mobile and localized holes near the top of the valence band play the role of unoccupied p-orbitals which induce ferromagnetism. T{sub c} estimated from the proposed kinematic exchange agrees with experiments on (Ga,Mn)As. The model is also applicable to the p-doped (Ga,Mn)P system. The magnetic ordering in n-type (Ga,Mn)N is due to exchange between the electrons localized on the levels lying deep in the forbidden energy gap. This mechanism is even closer to the original Zener mechanism.

  17. Quantum processes in semiconductors

    CERN Document Server

    Ridley, B K


    Aimed at graduate students, this is a guide to quantum processes of importance in the physics and technology of semiconductors. The fifth edition includes new chapters that expand the coverage of semiconductor physics relevant to its accompanying technology.

  18. Metal-doped semiconductor nanoparticles and methods of synthesis thereof (United States)

    Ren, Zhifeng (Inventor); Chen, Gang (Inventor); Poudel, Bed (Inventor); Kumar, Shankar (Inventor); Wang, Wenzhong (Inventor); Dresselhaus, Mildred (Inventor)


    The present invention generally relates to binary or higher order semiconductor nanoparticles doped with a metallic element, and thermoelectric compositions incorporating such nanoparticles. In one aspect, the present invention provides a thermoelectric composition comprising a plurality of nanoparticles each of which includes an alloy matrix formed of a Group IV element and Group VI element and a metallic dopant distributed within the matrix.

  19. Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer (United States)

    Spahn, Olga B.; Lear, Kevin L.


    A semiconductor structure. The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g. Al.sub.2 O.sub.3), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3-1.6 .mu.m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation.

  20. The Einstein relation in quantum wires of III-V, ternary, and quaternary materials in the presence of light waves: Simplified theory, relative comparison, and suggestion for experimental determination

    NARCIS (Netherlands)

    Ghatak, K.P.; Bhattacharya, S.; Bhowmik, S.; Benedictus, R.; Choudhury, S.


    We study the Einstein relation for the diffusivity to mobility ratio (DMR) in quantum wires (QWs) of III-V, ternary, and quaternary materials in the presence of light waves, whose unperturbed energy band structures are defined by the three band model of Kane. It has been found, taking n-InAs, n-InSb

  1. “Direct modulation of a hybrid III-V/Si DFB laser with MRR filtering for 22.5-Gb/s error-free dispersion-uncompensated transmission over 2.5-km SSMF

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Da Ros, Francesco; Ding, Yunhong;


    Error-free and penalty-free transmission over 2.5 km SSMF of a 22.5 Gb/s data signal from a directly modulated hybrid III-V/Si DFB laser is achieved by enhancing the dispersion tolerance using a silicon micro-ring resonator....

  2. Influence of light on the Einstein relation in III V, ternary and quaternary materials: Simplified theory and a suggestion for experimental determination (United States)

    Mukherjee, S.; De, D.; Mukherjee, D. J.; Bhattacharya, S.; Sinha, A.; Ghatak, K. P.


    We study theoretically the energy spectrum of the conduction electrons and the Einstein relation for the diffusivity-mobility ratio (DMR) for III-V, ternary and quaternary materials, whose unperturbed energy band structures are defined by the three-band model of Kane, in the presence of light waves. The solution of the Boltzmann transport equation on the basis of this newly formulated electron dispersion law will introduce new physical ideas and experimental findings under different external conditions. It has been observed that the unperturbed isotropic energy spectrum in the presence of light changes into an anisotropic dispersion relation with the energy-dependent mass anisotropy. It has been found taking n-InAs, n-InSb, n-Hg 1-xCd xTe and n-In 1-xGa xAs yP 1-y lattice matched to InP, as examples that the DMR increases with increasing electron concentration, decreasing with increasing intensity and wavelength in various manners. The rate of change is totally band structure dependent and is influenced by the presence of the different energy band constants. The well-known result for the DMR for degenerate wide gap materials in the absence of light waves has been obtained as a special case of the present analysis under certain limiting conditions and this compatibility is the indirect test of our generalized formalism. Besides, we have suggested an experimental method of determining the DMR in degenerate materials having arbitrary dispersion laws.

  3. Unitary lens semiconductor device (United States)

    Lear, Kevin L.


    A unitary lens semiconductor device and method. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors.

  4. The ATLAS semiconductor tracker (SCT)

    CERN Document Server

    Jackson, J N


    The ATLAS detector (CERN/LHCC/94-43 (1994)) is designed to study a wide range of physics at the CERN Large Hadron Collider (LHC) at luminosities up to 10**3**4 cm**-**2 s**-**1 with a bunch-crossing rate of 40 MHz. The Semiconductor Tracker (SCT) forms a key component of the Inner Detector (vol. 1, ATLAS TDR 4, CERN/LHCC 97-16 (1997); vol. 2, ATLAS TDR 5, CERN/LHCC 97-17 (1997)) which is situated inside a 2 T solenoid field. The ATLAS Semiconductor Tracker (SCT) utilises 4088 silicon modules with binary readout mounted on carbon fibre composite structures arranged in the forms of barrels in the central region and discs in the forward region. The construction of the SCT is now well advanced. The design of the SCT modules, services and support structures will be briefly outlined. A description of the various stages in the construction process will be presented with examples of the performance achieved and the main difficulties encountered. Finally, the current status of the construction is reviewed.

  5. Nanoscale Semiconductor Electronics (United States)


    create a brand -new process technology for the nano- fabrication of III-V devices. The radiation effects on these devices has been tested in AFRL...34Hydrolization oxidation of AlxGa1-xAs/GaAs quantum well heterostructures and superlattices," Appl . Phys. Lett. 57, 2844, 1990. [7] H. Wada and T. Kamijoh...942, Jun 1997. [8] H. Wada and T. Kamijoh, “Effects of Heat Treatment on Bonding Properties in InP-to- Si Direct Wafer Bonding,” Jpn. J. Appl

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

    Directory of Open Access Journals (Sweden)

    Bouhafs B.


    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.

  7. Influence of light on the Einstein relation in III-V, ternary and quaternary materials: Simplified theory and a suggestion for experimental determination

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, S. [Department of Electronic Science, University of Calcutta, 92, Achryya Prafulla Chandra Road, Kolkata 700 009 (India); De, D. [Department of Computer Science and Engineering, West Bengal University of Technology, B.F. 142, Sector 1, Salt Lake City, Kolkata 700 064 (India); Mukherjee, D.J. [Department of Electronics, Shyamaprasad College, 32, R. Dasgupta Road, Kolkata 700 024 (India); Bhattacharya, S. [Department of Computer Science, St. Xavier' s College, 30 Park Street, Kolkata 700 016 (India); Sinha, A. [Department of Physics, Kalyani University, Kalyani 741 235 (India); Ghatak, K.P. [Department of Electronic Science, University of Calcutta, 92, Achryya Prafulla Chandra Road, Kolkata 700 009 (India)]. E-mail:


    We study theoretically the energy spectrum of the conduction electrons and the Einstein relation for the diffusivity-mobility ratio (DMR) for III-V, ternary and quaternary materials, whose unperturbed energy band structures are defined by the three-band model of Kane, in the presence of light waves. The solution of the Boltzmann transport equation on the basis of this newly formulated electron dispersion law will introduce new physical ideas and experimental findings under different external conditions. It has been observed that the unperturbed isotropic energy spectrum in the presence of light changes into an anisotropic dispersion relation with the energy-dependent mass anisotropy. It has been found taking n-InAs, n-InSb, n-Hg{sub 1-} {sub x} Cd {sub x} Te and n-In{sub 1-} {sub x} Ga {sub x} As {sub y} P{sub 1-} {sub y} lattice matched to InP, as examples that the DMR increases with increasing electron concentration, decreasing with increasing intensity and wavelength in various manners. The rate of change is totally band structure dependent and is influenced by the presence of the different energy band constants. The well-known result for the DMR for degenerate wide gap materials in the absence of light waves has been obtained as a special case of the present analysis under certain limiting conditions and this compatibility is the indirect test of our generalized formalism. Besides, we have suggested an experimental method of determining the DMR in degenerate materials having arbitrary dispersion laws.

  8. Eclipsing binaries in open clusters

    DEFF Research Database (Denmark)

    Southworth, John; Clausen, J.V.


    Stars: fundamental parameters - Stars : binaries : eclipsing - Stars: Binaries: spectroscopic - Open clusters and ass. : general Udgivelsesdato: 5 August......Stars: fundamental parameters - Stars : binaries : eclipsing - Stars: Binaries: spectroscopic - Open clusters and ass. : general Udgivelsesdato: 5 August...

  9. Semiconductor Physical Electronics

    CERN Document Server

    Li, Sheng


    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...

  10. Infrared Semiconductor Metamaterials (United States)


    AFRL-AFOSR-VA-TR-2016-0310 Infrared Semiconductor Metamaterials Jon Schuller UNIVERSITY OF CALIFORNIA SANTA BARBARA 3227 CHEADLE HL SANTA BARBARA, CA...From - To) 15-07-2013 to 14-07-2016 4. TITLE AND SUBTITLE Infrared Semiconductor Metamaterials 5a. CONTRACT NUMBER FA9550-13-1-0182 5b. GRANT...program are 1) establishing an approach for widely tunable resonators and metasurfaces 2) experimentally demonstrating widely tunable semiconductor

  11. On the nature of ferromagnetism in dilute magnetic semiconductors: GaAs:Mn and GaP:Mn

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, V.A. E-mail:; Krstajic, P.M.; Peeters, F.M.; Fleurov, V.; Kikoin, K


    On the basis of a simplified Hamiltonian for transition metal impurities in diluted magnetic semiconductors (DMS), the nature of ferromagnetism in p-type III-V DMS are investigated. Ferromagnetism is governed by the Anderson-Hubbard parameter for 3d electrons of Mn{sup 2+} and their strong hybridization with the hole carriers in the semiconducting medium. The origin of ferromagnetism in these materials has similarity with the Zener mechanism. From the energetically preferable parallel orientation of Mn spins the Curie temperature is calculated for GaAs:Mn.

  12. Semiconductor bridge (SCB) detonator (United States)

    Bickes, Jr., Robert W.; Grubelich, Mark C.


    The present invention is a low-energy detonator for high-density secondary-explosive materials initiated by a semiconductor bridge igniter that comprises a pair of electrically conductive lands connected by a semiconductor bridge. The semiconductor bridge is in operational or direct contact with the explosive material, whereby current flowing through the semiconductor bridge causes initiation of the explosive material. Header wires connected to the electrically-conductive lands and electrical feed-throughs of the header posts of explosive devices, are substantially coaxial to the direction of current flow through the SCB, i.e., substantially coaxial to the SCB length.

  13. Semiconductor Electrical Measurements Laboratory (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...

  14. Semiconductor/dielectric interface engineering and characterization (United States)

    Lucero, Antonio T.

    The focus of this dissertation is the application and characterization of several, novel interface passivation techniques for III-V semiconductors, and the development of an in-situ electrical characterization. Two different interface passivation techniques were evaluated. The first is interface nitridation using a nitrogen radical plasma source. The nitrogen radical plasma generator is a unique system which is capable of producing a large flux of N-radicals free of energetic ions. This was applied to Si and the surface was studied using x-ray photoelectron spectroscopy (XPS). Ultra-thin nitride layers could be formed from 200-400° C. Metal-oxide-semiconductor capacitors (MOSCAPs) were fabricated using this passivation technique. Interface nitridation was able to reduce leakage current and improve the equivalent oxide thickness of the devices. The second passivation technique studied is the atomic layer deposition (ALD) diethylzinc (DEZ)/water treatment of sulfur treated InGaAs and GaSb. On InGaAs this passivation technique is able to chemically reduce higher oxidation states on the surface, and the process results in the deposition of a ZnS/ZnO interface passivation layer, as determined by XPS. Capacitance-voltage (C-V) measurements of MOSCAPs made on p-InGaAs reveal a large reduction in accumulation dispersion and a reduction in the density of interfacial traps. The same technique was applied to GaSb and the process was studied in an in-situ half-cycle XPS experiment. DEZ/H2O is able to remove all Sb-S from the surface, forming a stable ZnS passivation layer. This passivation layer is resistant to further reoxidation during dielectric deposition. The final part of this dissertation is the design and construction of an ultra-high vacuum cluster tool for in-situ electrical characterization. The system consists of three deposition chambers coupled to an electrical probe station. With this setup, devices can be processed and subsequently electrically characterized

  15. Near-field optical second-harmonic technique for detection and characterization of semiconductor thin film electron-scattering domain boundaries (United States)

    Shafiei, Farbod; Orzali, Tommaso; Bersuker, Gennadi; Michael, Downer


    Understanding electron transport in epitaxial semiconductor thin films and low dimension systems is crucial for new electro-optic devices. III-V films grown on Si integrate high carrier mobility into the established Si platform, but are susceptible to formation of sub-micron anti-phase domains that possess unwanted Ga-Ga or As-As electron-scattering defects at their boundaries. Optical second-harmonic generation provides sensitive, specific and noninvasive but so far only spatially-integrated characterization for these defects. We introduce a fiber based nearfield scanning optical second harmonic microscopy for the first time to fully resolve the electron scattering boundaries on III-V/Si films. This technique reveal variations in electron scattering boundaries structure as growth conditions, epitaxial film composition, and substrate vary, and are compared with surface topography, darkfield transmission electron microscopy and electron back scatter diffraction. Suppression of the electron-scattering boundaries has been explored.

  16. Binary mask programmable hologram. (United States)

    Tsang, P W M; Poon, T-C; Zhou, Changhe; Cheung, K W K


    We report, for the first time, the concept and generation of a novel Fresnel hologram called the digital binary mask programmable hologram (BMPH). A BMPH is comprised of a static, high resolution binary grating that is overlaid with a lower resolution binary mask. The reconstructed image of the BMPH can be programmed to approximate a target image (including both intensity and depth information) by configuring the pattern of the binary mask with a simple genetic algorithm (SGA). As the low resolution binary mask can be realized with less stringent display technology, our method enables the development of simple and economical holographic video display.

  17. Absorption enhancement of GaInP nanowires by tailoring transparent shell thicknesses and its application in III-V nanowire/Si film two-junction solar cells. (United States)

    Li, Xinhua; Shi, Tongfei; Liu, Guangqiang; Wen, Long; Zhou, BuKang; Wang, Yuqi


    A non-absorbing transparent shell is proposed to be coated on the outer surface of the core photoactive GaInP nanowire array (NWA) of the III-V nanowire (NW)/Si film two-junction solar cell. Interestingly, the diluted (at the filling ratio of 0.25) GaInP NWA with core / transparent shell structure can absorb more light than that in bare denser (at the filling ratio of 0.5) NWA. This allows for less source material consumption during the fabrication of III-V NWA/Si film two-junction cell. Meanwhile, the condition of current matching between the top III-V NWA and Si film sub cell can be easily fulfilled by tailoring the coating thickness of the transparent coating. Beyond the advantages on light absorption, the surface passivation effects introduced by the addition of some transparent dielectric coatings can reduce the surface recombination rate at the top NWA sub cell surface. This facilitates the effective extraction of photo-generated carriers and enhances output stability of the top NWA sub cell. From electrical simulation, a power conversion efficiency of 29.9% can be obtained at the optimized coating geometry.

  18. III-nitride semiconductors and their modern devices

    CERN Document Server


    This book is dedicated to GaN and its alloys AlGaInN (III-V nitrides), semiconductors with intrinsic properties well suited for visible and UV light emission and electronic devices working at high temperature, high frequency, and harsh environments. There has been a rapid growth in the industrial activity relating to GaN, with GaN now ranking at the second position (after Si) among all semiconductors. This is mainly thanks to LEDs, but also to the emergence of lasers and high power and high frequency electronics. GaN-related research activities are also diversifying, ranging from advanced optical sources and single electron devices to physical, chemical, and biological sensors, optical detectors, and energy converters. All recent developments of nitrides and of their technology are gathered here in a single volume, with chapters written by world leaders in the field. This third book of the series edited by B. Gil is complementary to the preceding two, and is expected to offer a modern vision of nitrides and...

  19. Ways of providing radiation resistance of magnetic field semiconductor sensors

    CERN Document Server

    Bolshakova, I A; Holyaka, R; Matkovskii, A; Moroz, A


    Hall magnetic field sensors resistant to hard ionizing irradiation are being developed for operation under the radiation conditions of space and in charged particle accelerators. Radiation resistance of the sensors is first determined by the properties of semiconductor materials of sensitive elements; we have used microcrystals and thin layers of III-V semiconductors. Applying complex doping by rare-earth elements and isovalent impurities in certain proportions, we have obtained magnetic field sensors resistant to irradiation by fast neutrons and gamma-quanta. Tests of their radiation resistance were carried out at IBR-2 at the Joint Institute for Nuclear Research (Dubna). When exposed to neutrons with E=0.1-13 MeV and intensity of 10 sup 1 sup 0 n cm sup - sup 2 s sup - sup 1 , the main parameter of the sensors - their sensitivity to magnetic fields - changes by no more than 0.1% up to fluences of 10 sup 1 sup 4 n cm sup - sup 2. Further improvement of radiation resistance of sensor materials is expected by ...

  20. Semiconductor Research Experimental Techniques

    CERN Document Server

    Balkan, Naci


    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.

  1. Semiconductors data handbook

    CERN Document Server

    Madelung, Otfried


    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

  2. Applications of Semiconductor Lasers

    Institute of Scientific and Technical Information of China (English)

    LI Te; SUN Yan-fang; NING Yong-qiang; WANG Li-jun


    An overview of the applications of semiconductor lasers is presented. Diode lasers are widely used today,and the most prevalent use of the laser is probably in CD and DVD drives for computers and audio/video media systems. Semiconductor lasers are also used in many other fields ranging from optical fiber communications to display,medicine and pumping sources.

  3. Semiconductor radiation detection systems

    CERN Document Server


    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.

  4. Terahertz semiconductor nonlinear optics

    DEFF Research Database (Denmark)

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


    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...... nonlinearity in doped semiconductors originates from the near-instantaneous heating of free electrons in the ponderomotive potential created by electric field of the THz pulse, leading to ultrafast increase of electron effective mass by intervalley scattering. Modification of effective mass in turn leads...... to a decrease of plasma frequency in semiconductor and produces a substantial modification of THz-range material dielectric function, described by the Drude model. As a result, the nonlinearity of both absorption coefficient and refractive index of the semiconductor is observed. In particular we demonstrate...

  5. Compound Semiconductor Radiation Detectors

    CERN Document Server

    Owens, Alan


    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...

  6. Semiconductor Nanowires from Materials Science and Device Physics Perspectives (United States)

    Samuelson, Lars


    Realization of extremely down-scaled devices gives tough challenges related to technology and materials science. One reason for the concern is that top-down fabricated nano-devices tend to have their properties dominated by process-induced damage, rendering ultra-small devices not so useful. Alternatively, bottom-up fabrication methods may allow dimensions on the scale even below 10 nm, still with superb device properties. I will in this talk describe our research on catalytically induced growth of semiconductor nanowires. Our method uses catalytic gold nanoparticles, allowing tight control of diameter as well as position of where the nanowire grows, with our work completely focused on epitaxially nucleated nanowires in which the nanowire structure can be seen as a coherent, monolithic extension of the crystalline substrate material. One of the most important achievements in this field of research is the realization of atomically abrupt heterostructures within nanowires, in which the material composition can be altered within only one or a few monolayers, thus allowing 1D heterostructure devices to be realized. This has allowed a variety of quantum devices to be realized, such as single-electron transistors, resonant tunneling devices as well as memory storage devices. A related recent field of progress has been the realization of ideally nucleated III-V nanowires on Si substrates, cases where we have also reported functioning III-V heterostructure device structures on Si. All of these device related challenges evolve from an improved understanding of the materials science involved in nucleation of nanowires, in altering of composition of the growing nanowire, in control of the growth direction etc. I will give examples of these materials science issues and will especially dwell on the opportunities to form new kinds of materials, e.g. as 3D complex nanowire structures, resembling nanotrees or nanoforests.

  7. Electrochemical Characterization of Semiconductor Materials and Structures (United States)


    For a period covering October 1, 1995 through August 12, 1996, the research group at CSU has conducted theoretical and experimental research on "Electrochemical Characterization of Semiconductor Materials and Structures. " The objective of this investigation was to demonstrate the applicability of electrochemical techniques for characterization of complex device structures based on InP and GaAs, Ge, InGaAs, InSb, InAs and InSb, including: (1) accurate EC-V net majority carrier concentration depth profiling, and (2) surface and bulk structural and electrical type defect densities. Our motivation for this R&D effort was as follows: "Advanced space solar cells and ThermoPhotoVoltaic (TPV) cells are fabricated using a large variety of III-V materials based on InP and GaAs for solar cells and low bandgap materials such as Ge, InGaAs, InAs and InSb for TPV applications. At the present time for complex device structures using these materials, however, there is no simple way to assess the quality of these structures prior to device fabrication. Therefore, process optimization is a very time consuming and a costly endeavor". Completion of this R&D effort would have had unquestionable benefits for space solar cell and TPV cells, since electrochemical characterization of the above cell structures, if properly designed can provide many useful structural and electrical material information virtually at any depth inside various layers and at the interfaces. This, could have been applied for step-by-step process optimization, which could have been used for fabrication of new generation high efficiency, low cost space PV and TPV cells.

  8. Semiconductors bonds and bands

    CERN Document Server

    Ferry, David K


    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. Physics of semiconductor lasers

    CERN Document Server

    Mroziewicz, B; Nakwaski, W


    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

  10. Defects in semiconductors

    CERN Document Server

    Romano, Lucia; Jagadish, Chennupati


    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

  11. Coherent dynamics in semiconductors

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher


    Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... and molecular systems are found and studied in the exciton-biexciton system of semiconductors. At densities where strong exciton interactions, or many-body effects, become dominant, the semiconductor Bloch equations present a more rigorous treatment of the phenomena Ultrafast degenerate four-wave mixing is used...

  12. Interacting binary stars

    CERN Document Server

    Sahade, Jorge; Ter Haar, D


    Interacting Binary Stars deals with the development, ideas, and problems in the study of interacting binary stars. The book consolidates the information that is scattered over many publications and papers and gives an account of important discoveries with relevant historical background. Chapters are devoted to the presentation and discussion of the different facets of the field, such as historical account of the development in the field of study of binary stars; the Roche equipotential surfaces; methods and techniques in space astronomy; and enumeration of binary star systems that are studied

  13. Physics of semiconductor devices

    CERN Document Server

    Rudan, Massimo


    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...

  14. Defects in semiconductor nanostructures

    Indian Academy of Sciences (India)

    Vijay A Singh; Manoj K Harbola; Praveen Pathak


    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.

  15. Biggest semiconductor installed

    CERN Multimedia


    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.

  16. Isotopically controlled semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Haller, E.E.


    A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.

  17. A semiconductor laser

    Energy Technology Data Exchange (ETDEWEB)

    Naoko, O.; Masaru, K.


    A semiconductor laser with enhanced characteristics is patented in which bleaching coatings are generated on the outcoupling mirrors by sputtering alternating coating layers made from A1203 and A10, with high and low indices of refraction.

  18. Radiation effects in semiconductors

    CERN Document Server


    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


    This state-of-the-art survey on silicon carbide for semiconductors includes a bibliography of the most important references published as of the end...of 1964. The various methods used for growing silicon carbide single crystals are reviewed, as well as their properties and devices fabricated from...them. The fact that the state of-the-art of silicon carbide semiconductors is not further advanced may be attributed to the difficulties of growing

  20. Modified Binary Exponential Backoff Algorithm to Minimize Mobiles Communication Time


    Ibrahim Sayed Ahmad; Ali Kalakech; Seifedine Kadry


    the field of Wireless Local Area Networks (LANs) is expanding rapidly as a result of advances in digital communications, portable computers, and semiconductor technology. The early adopters of this technology have primarily been vertical application that places a premium on the mobility offered by such systems. Binary Exponential Backoff (BEB) refers to a collision resolution mechanism used in random access MAC protocols. This algorithm is used in Ethernet (IEEE 802.3) wired LANs. In Ethe...

  1. The 3-5 semiconductor solid solution single crystal growth. [low gravity float zone growth experiments using gallium indium antimonides and cadmium tellurides (United States)

    Gertner, E. R.


    Techniques used for liquid and vapor phase epitaxy of gallium indium arsenide are described and the difficulties encountered are examined. Results show that the growth of bulk III-V solid solution single crystals in a low gravity environment will not have a major technological impact. The float zone technique in a low gravity environment is demonstrated using cadmium telluride. It is shown that this approach can result in the synthesis of a class of semiconductors that can not be grown in normal gravity because of growth problems rooted in the nature of their phase diagrams.

  2. Simulation study of 14-nm-gate III-V trigate field effect transistor devices with In1-xGaxAs channel capping layer (United States)

    Huang, Cheng-Hao; Li, Yiming


    In this work, we study characteristics of 14-nm-gate InGaAs-based trigate MOSFET (metal-oxide-semiconductor field effect transistor) devices with a channel capping layer. The impacts of thickness and gallium (Ga) concentration of the channel capping layer on the device characteristic are firstly simulated and optimized by using three-dimensional quantum-mechanically corrected device simulation. Devices with In1-xGaxAs/In0.53Ga0.47As channels have the large driving current owing to small energy band gap and low alloy scattering at the channel surface. By simultaneously considering various physical and switching properties, a 4-nm-thick In0.68Ga0.32As channel capping layer can be adopted for advanced applications. Under the optimized channel parameters, we further examine the effects of channel fin angle and the work-function fluctuation (WKF) resulting from nano-sized metal grains of NiSi gate on the characteristic degradation and variability. To maintain the device characteristics and achieve the minimal variation induced by WKF, the physical findings of this study indicate a critical channel fin angle of 85o is needed for the device with an averaged grain size of NiSi below 4x4 nm2.

  3. Simulation study of 14-nm-gate III-V trigate field effect transistor devices with In1−xGaxAs channel capping layer

    Directory of Open Access Journals (Sweden)

    Cheng-Hao Huang


    Full Text Available In this work, we study characteristics of 14-nm-gate InGaAs-based trigate MOSFET (metal-oxide-semiconductor field effect transistor devices with a channel capping layer. The impacts of thickness and gallium (Ga concentration of the channel capping layer on the device characteristic are firstly simulated and optimized by using three-dimensional quantum-mechanically corrected device simulation. Devices with In1−xGaxAs/In0.53Ga0.47As channels have the large driving current owing to small energy band gap and low alloy scattering at the channel surface. By simultaneously considering various physical and switching properties, a 4-nm-thick In0.68Ga0.32As channel capping layer can be adopted for advanced applications. Under the optimized channel parameters, we further examine the effects of channel fin angle and the work-function fluctuation (WKF resulting from nano-sized metal grains of NiSi gate on the characteristic degradation and variability. To maintain the device characteristics and achieve the minimal variation induced by WKF, the physical findings of this study indicate a critical channel fin angle of 85o is needed for the device with an averaged grain size of NiSi below 4x4 nm2.

  4. Method of doping a semiconductor (United States)

    Yang, Chiang Y.; Rapp, Robert A.


    A method for doping semiconductor material. An interface is established between a solid electrolyte and a semiconductor to be doped. The electrolyte is chosen to be an ionic conductor of the selected impurity and the semiconductor material and electrolyte are jointly chosen so that any compound formed from the impurity and the semiconductor will have a free energy no lower than the electrolyte. A potential is then established across the interface so as to allow the impurity ions to diffuse into the semiconductor. In one embodiment the semiconductor and electrolyte may be heated so as to increase the diffusion coefficient.

  5. Basic Semiconductor Physics

    CERN Document Server

    Hamaguchi, Chihiro


    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...

  6. Fundamentals of semiconductor lasers

    CERN Document Server

    Numai, Takahiro


    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. Beyond amorphous organic semiconductors (United States)

    Hanna, Jun-ichi


    Recently it has been discovered that some types of liquid crystals, which believed to be governed by ionic conduction, exhibit a very fast electronic conduction. Their charge carrier transport is characterized by high mobility over 10-2 cm2/Vs independent of electric field and temperature. Now, the liquid crystals are being recognized as a new class of organic semiconductors. In this article, a new aspect of liquid crystals as a self-organizing molecular semiconductor are reviewed, focused on their basic charge carrier transport properties and discussed in comparison with those of molecular crystals and amorphous materials. And it is concluded that the liquid crystal is promising as a quality organic semiconductor for the devices that require a high mobility.

  8. Photoelectronic properties of semiconductors

    CERN Document Server

    Bube, Richard H


    The interaction between light and electrons in semiconductors forms the basis for many interesting and practically significant properties. This book examines the fundamental physics underlying this rich complexity of photoelectronic properties of semiconductors, and will familiarise the reader with the relatively simple models that are useful in describing these fundamentals. The basic physics is also illustrated with typical recent examples of experimental data and observations. Following introductory material on the basic concepts, the book moves on to consider a wide range of phenomena, including photoconductivity, recombination effects, photoelectronic methods of defect analysis, photoeffects at grain boundaries, amorphous semiconductors, photovoltaic effects and photoeffects in quantum wells and superlattices. The author is Professor of Materials Science and Electrical Engineering at Stanford University, and has taught this material for many years. He is an experienced author, his earlier books having fo...

  9. Electronic bandstructure and optical gain of lattice matched III-V dilute nitride bismide quantum wells for 1.55 μm optical communication systems (United States)

    Fan, W. J.; Bose, Sumanta; Zhang, D. H.


    Dilute nitride bismide GaNBiAs is a potential semiconductor alloy for near- and mid-infrared applications, particularly in 1.55 μm optical communication systems. Incorporating dilute amounts of bismuth (Bi) into GaAs reduces the effective bandgap rapidly, while significantly increasing the spin-orbit-splitting energy. Additional incorporation of dilute amounts of nitrogen (N) helps to attain lattice matching with GaAs, while providing a route for flexible bandgap tuning. Here we present a study of the electronic bandstructure and optical gain of the lattice matched GaNxBiy As1 -x -y /GaAs quaternary alloy quantum well (QW) based on the 16-band k .p model. We have taken into consideration the interactions between the N and Bi impurity states with the host material based on the band anticrossing and valence band anticrossing model. The optical gain calculation is based on the density matrix theory. We have considered different lattice matched GaNBiAs QW cases and studied their energy dispersion curves, optical gain spectrum, maximum optical gain, and differential gain and compared their performances based on these factors. The thickness and composition of these QWs were varied in order to keep the emission peak fixed at 1.55 μm. The well thickness has an effect on the spectral width of the gain curves. On the other hand, a variation in the injection carrier density has different effects on the maximum gain and differential gain of QWs of varying thicknesses. Among the cases studied, we found that the 6.3 nm thick GaN3 Bi5.17 As91.83 lattice matched QW was most suited for 1.55 μm (0.8 eV) GaAs-based photonic applications.

  10. GaAsPN-based PIN solar cells MBE-grown on GaP substrates: toward the III-V/Si tandem solar cell (United States)

    Da Silva, M.; Almosni, S.; Cornet, C.; Létoublon, A.; Levallois, C.; Rale, P.; Lombez, L.; Guillemoles, J.-F.; Durand, O.


    GaAsPN semiconductors are promising material for the elaboration of high efficiencies tandem solar cells on silicon substrates. GaAsPN diluted nitride alloy is studied as the top junction material due to its perfect lattice matching with the Si substrate and its ideal bandgap energy allowing a perfect current matching with the Si bottom cell. We review our recent progress in materials development of the GaAsPN alloy and our recent studies of some of the different building blocks toward the elaboration of a PIN solar cell. A lattice matched (with a GaP(001) substrate, as a first step toward the elaboration on a Si substrate) 1μm-thick GaAsPN alloy has been grown by MBE. After a post-growth annealing step, this alloy displays a strong absorption around 1.8-1.9 eV, and efficient photoluminescence at room temperature suitable for the elaboration of the targeted solar cell top junction. Early stage GaAsPN PIN solar cells prototypes have been grown on GaP (001) substrates, with 2 different absorber thicknesses (1μm and 0.3μm). The external quantum efficiencies and the I-V curves show that carriers have been extracted from the GaAsPN alloy absorbers, with an open-circuit voltage of 1.18 V, while displaying low short circuit currents meaning that the GaAsPN structural properties needs a further optimization. A better carrier extraction has been observed with the absorber displaying the smallest thickness, which is coherent with a low carriers diffusion length in our GaAsPN compound. Considering all the pathways for improvement, the efficiency obtained under AM1.5G is however promising.

  11. In situ definition of semiconductor structures by selective area growth and etching (United States)

    Colas, E.; Caneau, C.; Frei, M.; Clausen, E. M., Jr.; Quinn, W. E.; Kim, M. S.


    Selective area growth (etching) by low-pressure organometallic chemical vapor deposition (LP-OMCVD) is utilized to intentionally modulate the local growth (etch) rate by choosing the pattern of dielectric-masked areas, thereby defining III-V semiconductor structures in situ. This technique is applied to tune the emission wavelength of a GaAs/AlGaAs quantum well structure, and to obtain InP/InGaAs superlattice structures tapered in thickness with growth rate increases as high as 800%, suitable for integrated optics applications. In contrast, selective deposition by organometallic molecular beam epitaxy (OMMBE) does not produce growth rate enhancements, thereby preventing similar in situ definition schemes but allowing to integrate structures with optimized nominal thicknesses.

  12. Hybrid bandgap engineering for super-hetero-epitaxial semiconductor materials, and products thereof (United States)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)


    "Super-hetero-epitaxial" combinations comprise epitaxial growth of one material on a different material with different crystal structure. Compatible crystal structures may be identified using a "Tri-Unity" system. New bandgap engineering diagrams are provided for each class of combination, based on determination of hybrid lattice constants for the constituent materials in accordance with lattice-matching equations. Using known bandgap figures for previously tested materials, new materials with lattice constants that match desired substrates and have the desired bandgap properties may be formulated by reference to the diagrams and lattice matching equations. In one embodiment, this analysis makes it possible to formulate new super-hetero-epitaxial semiconductor systems, such as systems based on group IV alloys on c-plane LaF.sub.3; group IV alloys on c-plane langasite; Group III-V alloys on c-plane langasite; and group II-VI alloys on c-plane sapphire.

  13. Kuiper Binary Object Formation

    CERN Document Server

    Nazzario, R C; Covington, C; Kagan, D; Hyde, T W


    It has been observed that binary Kuiper Belt Objects (KBOs) exist contrary to theoretical expectations. Their creation presents problems to most current models. However, the inclusion of a third body (for example, one of the outer planets) may provide the conditions necessary for the formation of these objects. The presence of a third massive body not only helps to clear the primordial Kuiper Belt but can also result in long lived binary Kuiper belt objects. The gravitational interaction between the KBOs and the third body causes one of four effects; scattering into the Oort cloud, collisions with the growing protoplanets, formation of binary pairs, or creation of a single Kuiper belt object. Additionally, the initial location of the progenitors of the Kuiper belt objects also has a significant effect on binary formation.

  14. Optical processes in semiconductors

    CERN Document Server

    Pankove, Jacques I


    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

  15. Advances in semiconductor lasers

    CERN Document Server

    Coleman, James J; Jagadish, Chennupati


    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

  16. Introductory semiconductor device physics

    CERN Document Server

    Parker, Greg


    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

  17. Semiconductor opto-electronics

    CERN Document Server

    Moss, TS; Ellis, B


    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

  18. Ternary chalcopyrite semiconductors

    CERN Document Server

    Shay, J L; Pamplin, B R


    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

  19. Quantum Transport in Semiconductors (United States)


    SRS i 91 4. TITLE AND SUBTITLE Quantum Transport in Semiconductors 5. FUNDING NUMBER söMtos-rizk-ooss 6. AUTHOR(S) D. K. Ferry ©fte ELECTE...OF ABSTRACT UL NSN 7540-01-280-5500 O 1 9 Standard Form 298 (Rev. 2-89) Presented by ANSI Std «9-18 298-102 Final Report Quantum Transport in... Quantum Transport in Semiconductor Devices This final report describes a program of research investigating quantum effects which become important in

  20. Compound semiconductor device physics

    CERN Document Server

    Tiwari, Sandip


    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

  1. Semiconductor surface protection material (United States)

    Packard, R. D. (Inventor)


    A method and a product for protecting semiconductor surfaces is disclosed. The protective coating material is prepared by heating a suitable protective resin with an organic solvent which is solid at room temperature and converting the resulting solution into sheets by a conventional casting operation. Pieces of such sheets of suitable shape and thickness are placed on the semiconductor areas to be coated and heat and vacuum are then applied to melt the sheet and to drive off the solvent and cure the resin. A uniform adherent coating, free of bubbles and other defects, is thus obtained exactly where it is desired.

  2. Kuiper Binary Object Formation


    Nazzario, R. C.; Orr, K.; Covington, C.; Kagan, D.; Hyde, T. W.


    It has been observed that binary Kuiper Belt Objects (KBOs) exist contrary to theoretical expectations. Their creation presents problems to most current models. However, the inclusion of a third body (for example, one of the outer planets) may provide the conditions necessary for the formation of these objects. The presence of a third massive body not only helps to clear the primordial Kuiper Belt but can also result in long lived binary Kuiper belt objects. The gravitational interaction betw...

  3. Eclipsing Binary Pulsars

    CERN Document Server

    Freire, P C C


    The first eclipsing binary pulsar, PSR B1957+20, was discovered in 1987. Since then, 13 other eclipsing low-mass binary pulsars have been found, 12 of these are in globular clusters. In this paper we list the known eclipsing binary pulsars and their properties, with special attention to the eclipsing systems in 47 Tuc. We find that there are two fundamentally different groups of eclipsing binary pulsars; separated by their companion masses. The less massive systems (M_c ~ 0.02 M_sun) are a product of predictable stellar evolution in binary pulsars. The systems with more massive companions (M_c ~ 0.2 M_sun) were formed by exchange encounters in globular clusters, and for that reason are exclusive to those environments. This class of systems can be used to learn about the neutron star recycling fraction in the globular clusters actively forming pulsars. We suggest that most of these binary systems are undetectable at radio wavelengths.

  4. Handbook of luminescent semiconductor materials

    CERN Document Server

    Bergman, Leah


    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

  5. Metal semiconductor contacts and devices

    CERN Document Server

    Cohen, Simon S; Einspruch, Norman G


    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

  6. Study of LO-phonon decay in semiconductors for hot carrier solar cell (United States)

    Levard, Hugo; Vidal, Julien; Laribi, Sana; Guillemoles, Jean-François


    Knowledge of phonon decay is of crucial importance when studying basic properties of semiconductors, since they are closely related to Raman linewidth and non-equilibrium-hot-carriers cooling. The latter indeed cools down to the bottom of the conduction band within a picosecond range because of electron-phonon interaction. The eventual emitted hot phonons then decay in few picoseconds. The hot carriers cooling can be slowed down by considering the decay rate dependence of phonon on conservation rules, whose tuning may reduce the allowed two-phonon final states density. This is of direct interest for the third generation photovoltaic devices that are Hot Carrier Solar Cells (HCSC), in which the photoexcited carriers are extracted at an energy higher than thermal equilibrium. One of the HCSC main challenges then is to find an absorber material in which the hot phonons has a relaxation time longer than the carriers cooling time, so that we can expect the electron to ``reabsorb'' a phonon, slowing down the electronic cooling. HCSC yield is ultimately limited by LO phonon decay, though. In this work, we present theoretical results obtained from ab initio calculations of phonon lifetime in III-V and IV-IV semiconductors through a three-phonon process. Common approximations in the literature are questioned. In particular, we show that the usual ``zone-center approximation'' is not valid in some specific semiconductors. The analysis allows to correctly investigate phonon decay mechanisms in bulk and nanostructured materials.

  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. Optical Design of Dilute Nitride Quantum Wells Vertical Cavity Semiconductor Optical Amplifiers for Communication Systems

    Directory of Open Access Journals (Sweden)

    Faten A. Chaqmaqchee


    Full Text Available III-V semiconductors components such as Gallium Arsenic (GaAs, Indium Antimony (InSb, Aluminum Arsenic (AlAs and Indium Arsenic (InAs have high carrier mobilities and direct energy gaps. This is making them indispensable for today’s optoelectronic devices such as semiconductor lasers and optical amplifiers at 1.3 μm wavelength operation. In fact, these elements are led to the invention of the Gallium Indium Nitride Arsenic (GaInNAs, where the lattice is matched to GaAs for such applications. This article is aimed to design dilute nitride GaInNAs quantum wells (QWs enclosed between top and bottom of Aluminum (Gallium Arsenic Al(GaAs distributed bragg mirrors (DBRs using MATLAB® program. Vertical cavity semiconductor optical amplifiers (VCSOAs structures are based on Fabry Perot (FP method to design optical gain and bandwidth gain to be operated in reflection and transmission modes. The optical model gives access to the contact layer of epitaxial structure and the reflectivity for successive radiative modes, their lasing thresholds, emission wavelengths and optical field distributions in the laser cavity.

  9. Intense terahertz excitation of semiconductors

    CERN Document Server

    Ganichev, S D


    This work presents the first comprehensive treatment of high-power terahertz applications to semiconductors and low-dimensional semiconductor structures. Terahertz properties of semiconductors are in the centre of scientific activities because of the need of high-speed electronics.

  10. Vacancies and defect levels in III–V semiconductors

    KAUST Repository

    Tahini, H. A.


    Using electronic structure calculations, we systematically investigate the formation of vacancies in III-V semiconductors (III = Al, Ga, and In and V = P, As, and Sb), for a range of charges ( −3≤q≤3 ) as a function of the Fermi level and under different growth conditions. The formation energies were corrected using the scheme due to Freysoldt et al. [Phys. Rev. Lett. 102, 016402 (2009)] to account for finite size effects. Vacancy formation energies were found to decrease as the size of the group V atom increased. This trend was maintained for Al-V, Ga-V, and In-V compounds. The negative-U effect was only observed for the arsenic vacancy in GaAs, which makes a charge state transition from +1 to –1. It is also found that even under group III rich conditions, group III vacancies dominate in AlSb and GaSb. For InSb, group V vacancies are favoured even under group V rich conditions.

  11. Growth and Characterization of Semiconductor Nanostructures for Nanoelectronics (United States)

    Zhong, Jiebin

    Recently, semiconductor nanostructures have generated a continuously growing interest owing to their intriguing physical properties and potential for future technology development. Quasi-one-dimensional nanowires (NWs), usually defined as round or polyhedral shaped cross-sectional structures with a high aspect ratio of 1000 or more, is one of the most active research areas for nanoelectronics, optoelectronics and sensors. Precise controlled growth of NWs, including dimensions, growth rate, morphology, growth direction, and composition, is essential from the viewpoints of fundamental materials fabrication and their performance in future applications. However, there are still many challenges in the fabrication of NWs with controlled dimensions and properties. This dissertation focuses on investigating the fundamental synthesis aspects of epitaxially grown III-V NWs by chemical vapor deposition (CVD). First, gold (Au) catalyst-assisted growth of InSb NWs directly on lattice mismatched (˜7%) InAs (100) substrates have been studied. The influences of NW diameter and growth temperature on the NW growth rate and morphology have been investigated. The results indicate that NW growth is limited by the growth species direct impingement and the diffusion of surface adatoms. Next, the dependence of morphology of epitaxial InSb NWs on CVD growth parameters over InSb (100) substrates has been investigated. NW length and tapering factors correlated to morphological variations are determined as a function of growth parameters including growth temperature (300°C--480°C), powder source, and duration of growth. Results showed that NW morphology is influenced by axial and radial growth modes, reflecting the competition of various growth mechanisms under different growth conditions. We discovered that Indium droplets may also promote the growth of NWs with a similar role to that of catalytic Au nanoparticles. A potential growth model is accordingly described and discussed. An

  12. Biexcitons in semiconductor microcavities

    DEFF Research Database (Denmark)

    Borri, P.; Langbein, W.; Woggon, U.


    In this paper, the present status of the experimental study of the optical properties of biexcitons in semiconductor microcavities is reviewed. In particular, a detailed investigation of a polariton-biexciton transition in a high-quality single quantum well GaAs/AlGaAs microcavity is reported...

  13. Superconductivity in compensated and uncompensated semiconductors. (United States)

    Yanase, Youichi; Yorozu, Naoyuki


    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.

  14. Superconductivity in compensated and uncompensated semiconductors

    Directory of Open Access Journals (Sweden)

    Youichi Yanase and Naoyuki Yorozu


    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.

  15. EDITORIAL: Enhance your outlook with Compound Semiconductor (United States)

    Bedrock, Claire


    An overwhelming proportion of the articles published in this journal come under the heading of applied research. In this field research findings impact tomorrow's products, and so it's important to keep tabs on these developments. Grant applications, for example, can carry extra weight when the potential benefits to industry are outlined alongside the gains to fundamental science. What's more, it's just plain interesting to track how key breakthroughs in understanding can drive improvements in commercial devices. Within our publication group we offer free resources that can help you keep pace with trends in part of this sector. Compound Semiconductor magazine and its associated website,, cover III-V, III-N, SiC and SiGe research in academia and industry, alongside all the business news and key manufacturing technology. A high proportion of our authoritative and timely content is exclusive, and you can access it for free by completing a simple registration procedure at Three examples of feature articles published this year in Compound Semiconductor include: • Non-polar GaN reaches tipping point by Steven DenBaars, Shuji Nakamura and Jim Speck from the University of California, Santa Barbara. Although conventional GaN LEDs are a great commercial success, they suffer from an intrinsic weakness—internal electric fields that pull apart the electrons and holes and ultimately limit efficiency. However, this problem can be overcome by growing nitrides on alternate crystal planes. Although early attempts were unsuccessful, due to high defect densities in the epilayers, this is not the case with growth on the latest Mitsubishi substrates that can lead to external quantum efficiencies of 45%. In this article the authors describe the development of their non-polar material, and their promising results for LEDs and laser diodes. • Inverting the triple junction improves efficiency and flexibility by Paul Sharps and

  16. Electronic structure of semiconductor-metal-semiconductor heterostructures (United States)

    Masri, Pierre

    For the first time, we present in this article a microscopic self-consistent theory of the electronic structure of semiconductor-metal-semiconductor (SMS) heterostructures. This is done within the framework of a tight-binding approximation. We use a one-band model and a simplified two-band model to describe metal and semiconductor bulk bands, respectively. Results are given for a material-symmetrical and interface-assymetrical SMS structure: this involves the same semiconductors, but different interface polarities (anion- and cation-like interfaces). These results include metal-like states (built-in metal band) and metal-induced semiconductor-like states. The relevance of the charge neutrality condition to this feature and to the determination of the position of the SMS Fermi level is discussed. We also emphasize the confining role of interfaces, with respect to semiconductor-like states, within the semiconductor gap.

  17. Toward Ultrafast Spin Dynamics in Low Dimensional Semiconductors (United States)

    Chiu, Yi-Hsin

    Since the discovery of long spin relaxation times of itinerant electrons up to 100 nanoseconds and spin diffusion lengths over 100 mum in GaAs, extraordinary advances in semiconductor spintronics have been made in the past one and half decades. Incorporating spins in semiconductors requires the following essential capabilities: (i) injection of spins into semiconductors, (ii) manipulation of spins, and (iii) sensitive detection of spin coherence. The solutions to these challenges lie in a deeper understanding of spin interactions and spin relaxation in semiconductors as well as appropriate tools to probe spin dynamics. In particular, recent experiments have suggested the important role of dimensionality in spin dynamics. For example, spin-orbit interaction, the dominant source of spin relaxation in most II-VI and III-V semiconductors, has been shown to be significantly suppressed in reduced dimensions. Low-dimensional semiconductors are therefore appealing candidates for exploring spin physics and device applications. This dissertation aims at exploring spin dynamics in low dimensional semiconductor systems using time-resolved optical techniques. The time resolution allows for a direct measurement of the equilibrium and non-equilibrium carrier spins and various spin interactions in the time domain. Optical approaches are also a natural fit for probing optically active nanostructures where electric approaches can often encounter challenges. For instance, fabricating electric contacts with nanostructures is a proven challenge because of their reduced size and modified electronic structure. This dissertation is divided into three sections targeting an ultimate goal of employing optical methods to explore spin dynamics in low dimensional semiconductors. First, the time-resolved Kerr rotation technique is employed to study spin relaxation in Fe/MgO/GaAs heterostructures. The results reveal rich interactions between the GaAs electron spins, nuclear spins, and the

  18. Binary Masking & Speech Intelligibility

    DEFF Research Database (Denmark)

    Boldt, Jesper

    The purpose of this thesis is to examine how binary masking can be used to increase intelligibility in situations where hearing impaired listeners have difficulties understanding what is being said. The major part of the experiments carried out in this thesis can be categorized as either experime...... mask using a directional system and a method for correcting errors in the target binary mask. The last part of the thesis, proposes a new method for objective evaluation of speech intelligibility.......The purpose of this thesis is to examine how binary masking can be used to increase intelligibility in situations where hearing impaired listeners have difficulties understanding what is being said. The major part of the experiments carried out in this thesis can be categorized as either...... experiments under ideal conditions or as experiments under more realistic conditions useful for real-life applications such as hearing aids. In the experiments under ideal conditions, the previously defined ideal binary mask is evaluated using hearing impaired listeners, and a novel binary mask -- the target...

  19. Skewed Binary Search Trees

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Moruz, Gabriel


    It is well-known that to minimize the number of comparisons a binary search tree should be perfectly balanced. Previous work has shown that a dominating factor over the running time for a search is the number of cache faults performed, and that an appropriate memory layout of a binary search tree...... can reduce the number of cache faults by several hundred percent. Motivated by the fact that during a search branching to the left or right at a node does not necessarily have the same cost, e.g. because of branch prediction schemes, we in this paper study the class of skewed binary search trees....... For all nodes in a skewed binary search tree the ratio between the size of the left subtree and the size of the tree is a fixed constant (a ratio of 1/2 gives perfect balanced trees). In this paper we present an experimental study of various memory layouts of static skewed binary search trees, where each...

  20. Binary Neutron Star Mergers

    Directory of Open Access Journals (Sweden)

    Joshua A. Faber


    Full Text Available We review the current status of studies of the coalescence of binary neutron star systems. We begin with a discussion of the formation channels of merging binaries and we discuss the most recent theoretical predictions for merger rates. Next, we turn to the quasi-equilibrium formalisms that are used to study binaries prior to the merger phase and to generate initial data for fully dynamical simulations. The quasi-equilibrium approximation has played a key role in developing our understanding of the physics of binary coalescence and, in particular, of the orbital instability processes that can drive binaries to merger at the end of their lifetimes. We then turn to the numerical techniques used in dynamical simulations, including relativistic formalisms, (magneto-hydrodynamics, gravitational-wave extraction techniques, and nuclear microphysics treatments. This is followed by a summary of the simulations performed across the field to date, including the most recent results from both fully relativistic and microphysically detailed simulations. Finally, we discuss the likely directions for the field as we transition from the first to the second generation of gravitational-wave interferometers and while supercomputers reach the petascale frontier.

  1. Binary and Millisecond Pulsars

    Directory of Open Access Journals (Sweden)

    Lorimer Duncan R.


    Full Text Available We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1800. There are now 83 binary and millisecond pulsars associated with the disk of our Galaxy, and a further 140 pulsars in 26 of the Galactic globular clusters. Recent highlights include the discovery of the young relativistic binary system PSR J1906+0746, a rejuvination in globular cluster pulsar research including growing numbers of pulsars with masses in excess of 1.5M_⊙, a precise measurement of relativistic spin precession in the double pulsar system and a Galactic millisecond pulsar in an eccentric (e = 0.44 orbit around an unevolved companion.

  2. Binary Popldation Synthcsis Study

    Institute of Scientific and Technical Information of China (English)

    HAN Zhanwen


    Binary population synthesis (BPS), an approach to evolving millions of stars (including binaries) simultaneously, plays a crucial role in our understanding of stellar physics, the structure and evolution of galaxies, and cosmology. We proposed and developed a BPS approach, and used it to investigate the formation of many peculiar stars such as hot subdwarf stars, progenitors of type la supernovae, barium stars, CH stars, planetary nebulae, double white dwarfs, blue stragglers, contact binaries, etc. We also established an evolution population synthesis (EPS) model, the Yunnan Model, which takes into account binary interactions for the first time. We applied our model for the origin of hot subdwarf stars in the study of elliptical galaxies and explained their far-UV radiation.

  3. Compound semiconductor device modelling

    CERN Document Server

    Miles, Robert


    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...

  4. Stretchable Organic Semiconductor Devices. (United States)

    Qian, Yan; Zhang, Xinwen; Xie, Linghai; Qi, Dianpeng; Chandran, Bevita K; Chen, Xiaodong; Huang, Wei


    Stretchable electronics are essential for the development of intensely packed collapsible and portable electronics, wearable electronics, epidermal and bioimplanted electronics, 3D surface compliable devices, bionics, prosthesis, and robotics. However, most stretchable devices are currently based on inorganic electronics, whose high cost of fabrication and limited processing area make it difficult to produce inexpensive, large-area devices. Therefore, organic stretchable electronics are highly attractive due to many advantages over their inorganic counterparts, such as their light weight, flexibility, low cost and large-area solution-processing, the reproducible semiconductor resources, and the easy tuning of their properties via molecular tailoring. Among them, stretchable organic semiconductor devices have become a hot and fast-growing research field, in which great advances have been made in recent years. These fantastic advances are summarized here, focusing on stretchable organic field-effect transistors, light-emitting devices, solar cells, and memory devices.

  5. Polymer semiconductor crystals

    Directory of Open Access Journals (Sweden)

    Jung Ah Lim


    Full Text Available One of the long-standing challenges in the field of polymer semiconductors is to figure out how long interpenetrating and entangled polymer chains self-assemble into single crystals from the solution phase or melt. The ability to produce these crystalline solids has fascinated scientists from a broad range of backgrounds including physicists, chemists, and engineers. Scientists are still on the hunt for determining the mechanism of crystallization in these information-rich materials. Understanding the theory and concept of crystallization of polymer semiconductors will undoubtedly transform this area from an art to an area that will host a bandwagon of scientists and engineers. In this article we describe the basic concept of crystallization and highlight some of the advances in polymer crystallization from crystals to nanocrystalline fibers.

  6. Three dimensional strained semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Voss, Lars; Conway, Adam; Nikolic, Rebecca J.; Leao, Cedric Rocha; Shao, Qinghui


    In one embodiment, an apparatus includes a three dimensional structure comprising a semiconductor material, and at least one thin film in contact with at least one exterior surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the three dimensional structure. In another embodiment, a method includes forming a three dimensional structure comprising a semiconductor material, and depositing at least one thin film on at least one surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the structure.

  7. Semiconductor physics an introduction

    CERN Document Server

    Seeger, Karlheinz


    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.

  8. Doping of organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Luessem, B.; Riede, M.; Leo, K. [Institut fuer Angewandte Photophysik, TU Dresden (Germany)


    The understanding and applications of organic semiconductors have shown remarkable progress in recent years. This material class has been developed from being a lab curiosity to the basis of first successful products as small organic LED (OLED) displays; other areas of application such as OLED lighting and organic photovoltaics are on the verge of broad commercialization. Organic semiconductors are superior to inorganic ones for low-cost and large-area optoelectronics due to their flexibility, easy deposition, and broad variety, making tailor-made materials possible. However, electrical doping of organic semiconductors, i.e. the controlled adjustment of Fermi level that has been extremely important to the success of inorganic semiconductors, is still in its infancy. This review will discuss recent work on both fundamental principles and applications of doping, focused primarily to doping of evaporated organic layers with molecular dopants. Recently, both p- and n-type molecular dopants have been developed that lead to efficient and stable doping of organic thin films. Due to doping, the conductivity of the doped layers increases several orders of magnitude and allows for quasi-Ohmic contacts between organic layers and metal electrodes. Besides reducing voltage losses, doping thus also gives design freedom in terms of transport layer thickness and electrode choice. The use of doping in applications like OLEDs and organic solar cells is highlighted in this review. Overall, controlled molecular doping can be considered as key enabling technology for many different organic device types that can lead to significant improvements in efficiencies and lifetimes. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Semiconductors for organic transistors


    Antonio Facchetti


    Organic molecules/polymers with a π-conjugated (hetero)aromatic backbone are capable of transporting charge and interact efficiently with light. Therefore, these systems can act as semiconductors in opto-electronic devices similar to inorganic materials. However, organic chemistry offers tools for tailoring materials' functional properties via modifications of the molecular/monomeric units, opening new possibilities for inexpensive device manufacturing. This article reviews the fundamental as...

  10. Tunable Infrared Semiconductor Lasers (United States)


    Lett. 81, 406-408 (2002). [20] M. Ito and T. Kimura, “Oscillation properties of AlGaAs DH Lasrs with an external grating,” IEEE J. Quant. Elec- tron...tuning range has been demonstrated on a large area index-coupled, optically pumped mid-infrared type-II semiconductor distributed feedback (DFB) laser...lithography (IL) technique is used to pattern this chirped grating with two coherent spherical waves. A new grating fabrication optical arrangement

  11. Survey of semiconductor physics

    CERN Document Server

    Böer, Karl W


    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...

  12. Semiconductor Ion Implanters (United States)

    MacKinnon, Barry A.; Ruffell, John P.


    In 1953 the Raytheon CK722 transistor was priced at 7.60. Based upon this, an Intel Xeon Quad Core processor containing 820,000,000 transistors should list at 6.2 billion! Particle accelerator technology plays an important part in the remarkable story of why that Intel product can be purchased today for a few hundred dollars. Most people of the mid twentieth century would be astonished at the ubiquity of semiconductors in the products we now buy and use every day. Though relatively expensive in the nineteen fifties they now exist in a wide range of items from high-end multicore microprocessors like the Intel product to disposable items containing `only' hundreds or thousands like RFID chips and talking greeting cards. This historical development has been fueled by continuous advancement of the several individual technologies involved in the production of semiconductor devices including Ion Implantation and the charged particle beamlines at the heart of implant machines. In the course of its 40 year development, the worldwide implanter industry has reached annual sales levels around 2B, installed thousands of dedicated machines and directly employs thousands of workers. It represents in all these measures, as much and possibly more than any other industrial application of particle accelerator technology. This presentation discusses the history of implanter development. It touches on some of the people involved and on some of the developmental changes and challenges imposed as the requirements of the semiconductor industry evolved.

  13. Eclipsing Binary Update, No. 2. (United States)

    Williams, D. B.


    Contents: 1. Wrong again! The elusive period of DHK 41. 2. Stars observed and not observed. 3. Eclipsing binary chart information. 4. Eclipsing binary news and notes. 5. A note on SS Arietis. 6. Featured star: TX Ursae Majoris.

  14. Compressing Binary Decision Diagrams

    DEFF Research Database (Denmark)

    Hansen, Esben Rune; Satti, Srinivasa Rao; Tiedemann, Peter


    The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1...

  15. Compressing Binary Decision Diagrams

    DEFF Research Database (Denmark)

    Rune Hansen, Esben; Srinivasa Rao, S.; Tiedemann, Peter

    The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1...

  16. Orbits for sixteen binaries

    Directory of Open Access Journals (Sweden)

    Cvetković Z.


    Full Text Available In this paper orbits for 13 binaries are recalculated and presented. The reason is that recent observations show higher residuals than the corresponding ephemerides calculated by using the orbital elements given in the Sixth Catalog of Orbits of Visual Binary Stars. The binaries studied were: WDS 00182+7257 = A 803, WDS 00335+4006 = HO 3, WDS 00583+2124 = BU 302, WDS 01011+6022 = A 926, WDS 01014+1155 = BU 867, WDS 01112+4113 = A 655, WDS 01361−2954 + HJ 3447, WDS 02333+5219 = STT 42 AB,WDS 04362+0814 = A 1840 AB,WDS 08017−0836 = A 1580, WDS 08277−0425 = A 550, WDS 17471+1742 = STF 2215 and WDS 18025+4414 = BU 1127 Aa-B. In addition, for three binaries - WDS 01532+1526 = BU 260, WDS 02563+7253 = STF 312 AB and WDS 05003+3924 = STT 92 AB - the orbital elements are calculated for the first time. In this paper the authors present not only the orbital elements, but the masses dynamical parallaxes, absolute magnitudes and ephemerides for the next five years, as well.

  17. Equational binary decision diagrams

    NARCIS (Netherlands)

    Groote, J.F.; Pol, J.C. van de


    We incorporate equations in binary decision diagrams (BDD). The resulting objects are called EQ-BDDs. A straightforward notion of ordered EQ-BDDs (EQ-OBDD) is defined, and it is proved that each EQ-BDD is logically equivalent to an EQ-OBDD. Moreover, on EQ-OBDDs satisfiability and tautology checkin

  18. Black holes in binary stars

    NARCIS (Netherlands)

    Wijers, R.A.M.J.


    Introduction Distinguishing neutron stars and black holes Optical companions and dynamical masses X-ray signatures of the nature of a compact object Structure and evolution of black-hole binaries High-mass black-hole binaries Low-mass black-hole binaries Low-mass black holes Formation of black holes

  19. The development of intelligent expert system with SAT for semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Yeol; Shim, Jae Gi; Jeong, Hyun Jo; Cho, Young Tae; Kim, Chang Hyun; Ko, Myung Soo [Chosun University, Gwangju (Korea, Republic of)


    In this study, the researches classifying the artificial flaws in semiconductor packages are performed using pattern recognition technology. For this purposes image pattern recognition package including the user made software was developed and total procedure including ultrasonic image acquisition, equalization filtering, binary processing, edge detection and classifier selection is treated by BP(backpropagation). Specially, it is compared IP(image processing) and SOM(self-organizing map) as preprocessing method for dimensionality reduction for entrance into multi-layer perceptron(backpropagation). Also, the pattern recognition techniques is applied to the classification problem of semiconductor flaws as crack, delamination. According to this results, it is possible to acquire the recognition rate of 83.4% about delamination, 75.7% about crack for SOM, and to acquire the recognition rate of 100% for BP.

  20. Lattice location and local magnetism of recoil implanted Fe impurities in wide and narrow band semiconductors CdTe, CdSe, and InSb: Experiment and theory

    Energy Technology Data Exchange (ETDEWEB)

    Mohanta, S. K.; Mishra, S. N. [Tata Institute of Fundamental Research (TIFR), Homi Bhabha Road, Mumbai 400005 (India)


    Employing the time differential perturbed angular distribution method, we have measured local susceptibility and spin relaxation rate of {sup 54}Fe nuclei implanted in III-V and II-VI semiconductors, CdTe, CdSe, and InSb. The magnetic response of Fe, identified to occupy the metal as well as the semi-metal atom sites, exhibit Curie-Weiss type susceptibility and Korringa like spin relaxation rate, revealing the existence of localized moments with small spin fluctuation temperature. The experimental results are supported by first principle electronic structure calculations performed within the frame work of density functional theory.

  1. Learning to assign binary weights to binary descriptor (United States)

    Huang, Zhoudi; Wei, Zhenzhong; Zhang, Guangjun


    Constructing robust binary local feature descriptors are receiving increasing interest due to their binary nature, which can enable fast processing while requiring significantly less memory than their floating-point competitors. To bridge the performance gap between the binary and floating-point descriptors without increasing the computational cost of computing and matching, optimal binary weights are learning to assign to binary descriptor for considering each bit might contribute differently to the distinctiveness and robustness. Technically, a large-scale regularized optimization method is applied to learn float weights for each bit of the binary descriptor. Furthermore, binary approximation for the float weights is performed by utilizing an efficient alternatively greedy strategy, which can significantly improve the discriminative power while preserve fast matching advantage. Extensive experimental results on two challenging datasets (Brown dataset and Oxford dataset) demonstrate the effectiveness and efficiency of the proposed method.

  2. Electrodes for Semiconductor Gas Sensors. (United States)

    Lee, Sung Pil


    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.

  3. Semiconductor micropattern pixel detectors a review of the beginnings

    CERN Document Server

    Heijne, Erik H M


    The innovation in monolithic and hybrid semiconductor 'micropattern' or 'reactive' pixel detectors for tracking in particle physics was actually to fit logic and pulse processing electronics with µW power on a pixel area of less than 0.04 mm2, retaining the characteristics of a traditional nuclear amplifier chain. The ns timing precision in conjunction with local memory and logic operations allowed event selection at > 10 MHz rates with unambiguous track reconstruction even at particle multiplicities > 10 cm-2. The noise in a channel was ~100 e- r.m.s. and enabled binary operation with random noise 'hits' at a level 30 Mrad, respectively.

  4. Semiconductor solar cells: Recent progress in terrestrial applications (United States)

    Avrutin, V.; Izyumskaya, N.; Morkoç, H.


    In the last decade, the photovoltaic industry grew at a rate exceeding 30% per year. Currently, solar-cell modules based on single-crystal and large-grain polycrystalline silicon wafers comprise more than 80% of the market. Bulk Si photovoltaics, which benefit from the highly advanced growth and fabrication processes developed for microelectronics industry, is a mature technology. The light-to-electric power conversion efficiency of the best modules offered on the market is over 20%. While there is still room for improvement, the device performance is approaching the thermodynamic limit of ˜28% for single-junction Si solar cells. The major challenge that the bulk Si solar cells face is, however, the cost reduction. The potential for price reduction of electrical power generated by wafer-based Si modules is limited by the cost of bulk Si wafers, making the electrical power cost substantially higher than that generated by combustion of fossil fuels. One major strategy to bring down the cost of electricity generated by photovoltaic modules is thin-film solar cells, whose production does not require expensive semiconductor substrates and very high temperatures and thus allows decreasing the cost per unit area while retaining a reasonable efficiency. Thin-film solar cells based on amorphous, microcrystalline, and polycrystalline Si as well as cadmium telluride and copper indium diselenide compound semiconductors have already proved their commercial viability and their market share is increasing rapidly. Another avenue to reduce the cost of photovoltaic electricity is to increase the cell efficiency beyond the Shockley-Queisser limit. A variety of concepts proposed along this avenue forms the basis of the so-called third generation photovoltaics technologies. Among these approaches, high-efficiency multi-junction solar cells based on III-V compound semiconductors, which initially found uses in space applications, are now being developed for terrestrial applications. In

  5. Hydrogen in semiconductors

    CERN Document Server

    Pankove, Jacques I


    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

  6. Physics of Organic Semiconductors

    CERN Document Server

    Brütting, Wolfgang


    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

  7. Semiconductor microcavity polaritons

    Energy Technology Data Exchange (ETDEWEB)

    Vinogradov, Evgenii A [Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow region (Russian Federation)


    The optical properties of wide-gap semiconductor films on metal substrates were investigated experimentally by infrared spectroscopy, Raman scattering, and femtosecond spectroscopy techniques as well as theoretically in the framework of linear crystal optics. The optical spectra of such planar structures (microresonators) were shown to bear information on electromagnetic excitations of both the surface and the volume of the structure. The optical spectra are determined by the interaction of all dipole-active excitations of the component materials with the electromagnetic modes of the microresonator, which in turn are determined by the permittivities of each component material, microcavity (microresonator) thickness, and the experimental conditions. (reviews of topical problems)

  8. Electrowetting on semiconductors (United States)

    Palma, Cesar; Deegan, Robert


    Applying a voltage difference between a conductor and a sessile droplet sitting on a thin dielectric film separating it from the conductor will cause the drop to spread. When the conductor is a good metal, the change of the drop's contact angle due to the voltage is given by the Young-Lippmann (YL) equation. Here, we report experiments with lightly doped, single crystal silicon as the conductive electrode. We derive a modified YL equation that includes effects due to the semiconductor and contact line pinning. We show that light induces a non-reversible wetting transition, and that our model agrees well with our experimental results.

  9. Band structure of semiconductors

    CERN Document Server

    Tsidilkovski, I M


    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


    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. Semiconductor devices incorporating multilayer interference regions (United States)

    Biefeld, Robert M.; Drummond, Timothy J.; Gourley, Paul L.; Zipperian, Thomas E.


    A semiconductor high reflector comprising a number of thin alternating layers of semiconductor materials is electrically tunable and may be used as a temperature insensitive semiconductor laser in a Fabry-Perot configuration.

  12. Ultrafast Control of Magnetism in Ferromagnetic Semiconductors via Photoexcited Transient Carriers

    Energy Technology Data Exchange (ETDEWEB)

    Cotoros, Ingrid A. [Univ. of California, Berkeley, CA (United States)


    The field of spintronics offers perspectives for seamless integration of coupled and inter-tunable electrical and magnetic properties in a single device. For integration of the spin degree of freedom with current electronic technology, new semiconductors are needed that show electrically-tunable magnetic properties at room temperature and above. Dilute magnetic semiconductors derived from III-V compounds, like GaMnAs and InMnAs, show coupled and tunable magnetic, transport, and optical properties, due to the fact that their ferromagnetism is hole-mediated. These unconventional materials are ideal systems for manipulating the magnetic order by changing the carrier polarization, population density, and energy band distribution of the complementary subsystem of holes. This is the main theme we cover in this thesis. In particular, we develop a unique setup by use of ultraviolet pump, near-infrared probe femtosecond laser pulses, that allows for magneto-optical Kerr effect (MOKE) spectroscopy experiments. We photo-excite transient carriers in our samples, and measure the induced transient magnetization dynamics. One set of experiments performed allowed us to observe for the first time enhancement of the ferromagnetic order in GaMnAs, on an ultrafast time scale of hundreds of picoseconds. The corresponding transient increase of Curie temperature (Tc, the temperature above which a ferromagnetic material loses its permanent magnetism) of about 1 K for our experimental conditions is a very promising result for potential spintronics applications, especially since it is seconded by observation of an ultrafast ferromagnetic to paramagnetic phase transition above Tc. In a different set of experiments, we "write" the magnetization in a particular orientation in the sample plane. Using an ultrafast scheme, we alter the distribution of holes in the system and detect signatures of the particular memory state in the subsequent magnetization dynamics, with unprecedented hundreds of

  13. The Binary Garrote

    CERN Document Server

    Kappen, H J


    In this paper, I present a new model and solution method for sparse regression. The model introduces binary selector variables $s_i$ for the features $i$ in a way that is similar to Breiman's Garrote model. I refer to this method as the binary Garrote (BG). The posterior probability for $s_i$ is computed in the variational approximation. The BG is compared numerically with the Lasso method and with ridge regression. Numerical results on synthetic data show that the BG yields more accurate predictions and more accurately reconstructs the true model than the other methods. The naive implementation of the BG requires the inversion of a modified covariance matrix which scales cubic in the number of features. We indicate how for sparse problem the solution can be computed linear in the number of features.

  14. Binary Tetrahedral Flavor Symmetry

    CERN Document Server

    Eby, David A


    A study of the T' Model and its variants utilizing Binary Tetrahedral Flavor Symmetry. We begin with a description of the historical context and motivations for this theory, together with some conceptual background for added clarity, and an account of our theory's inception in previous works. Our model endeavors to bridge two categories of particles, leptons and quarks, a unification made possible by the inclusion of additional Higgs particles, shared between the two fermion sectors and creating a single coherent system. This is achieved through the use of the Binary Tetrahedral symmetry group and an investigation of the Tribimaximal symmetry evidenced by neutrinos. Our work details perturbations and extensions of this T' Model as we apply our framework to neutrino mixing, quark mixing, unification, and dark matter. Where possible, we evaluate model predictions against experimental results and find excellent matching with the atmospheric and reactor neutrino mixing angles, an accurate prediction of the Cabibb...

  15. Binary Love Relations

    CERN Document Server

    Yagi, Kent


    When in a tight binary, the mutual tidal deformations of neutron stars imprint onto observables, encoding information about their internal structure at supranuclear densities and gravity in the extreme-gravity regime. Gravitational wave observations of their late binary inspiral may serve as a tool to extract the individual tidal deformabilities, but this is made difficult by degeneracies between them in the gravitational wave model. We here resolve this problem by discovering approximately universal relations between dimensionless combinations of the individual tidal deformabilities. We show that these relations break degeneracies in the gravitational wave model, allowing for the accurate extraction of both deformabilities. Such measurements can be used to better differentiate between equation-of-state models, and improve tests of General Relativity and cosmology.

  16. Binary Love relations (United States)

    Yagi, Kent; Yunes, Nicolás


    When in a tight binary, the mutual tidal deformations of neutron stars get imprinted onto observables, encoding information about their internal structure at supranuclear densities and gravity in the extreme-gravity regime. Gravitational wave (GW) observations of their late binary inspiral may serve as a tool to extract the individual tidal deformabilities, but this is made difficult by degeneracies between them in the GW model. We here resolve this problem by discovering approximately equation-of-state (EoS)-insensitive relations between dimensionless combinations of the individual tidal deformabilities. We show that these relations break degeneracies in the GW model, allowing for the accurate extraction of both deformabilities. Such measurements can be used to better differentiate between EoS models, and improve tests of general relativity and cosmology.

  17. Squeezed light in semiconductors

    CERN Document Server

    Ward, M B


    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 ...

  18. Doped semiconductor nanocrystal junctions

    Energy Technology Data Exchange (ETDEWEB)

    Borowik, Ł.; Mélin, T., E-mail: [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)


    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.

  19. Hydrogen molecules in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Joerg [Technische Universitaet Dresden, 01062 Dresden (Germany)], E-mail:; Hiller, Martin; Lavrov, Edward V. [Technische Universitaet Dresden, 01062 Dresden (Germany)


    Molecular hydrogen, the simplest of all molecules, allows a direct insight into the fundamental properties of quantum mechanics. In the case of H{sub 2}, the Pauli principle leads to two different species, para-H{sub 2} and ortho-H{sub 2}. A conversion between these species is prohibited. Vibrational mode spectra reflect the fundamental properties and allow an unambiguous identification of the H{sub 2} molecules. Today, we have experimental evidence for the trapping of hydrogen molecules in the semiconductors Si, Ge and GaAs at the interstitial sites, within hydrogen-induced platelets, in voids and at impurities (interstitial oxygen in Si). Interstitial H{sub 2} is a nearly free rotor with a surprisingly simple behavior. We review on interstitial H{sub 2} in semiconductors and report on the unexpected preferential disappearance of the para-H{sub 2} or ortho-D{sub 2} species. The origin of the detected ortho-para conversion will be discussed.

  20. Direct solar-to-hydrogen conversion via inverted metamorphic multi-junction semiconductor architectures

    Energy Technology Data Exchange (ETDEWEB)

    Young, James L.; Steiner, Myles A.; Döscher, Henning; France, Ryan M.; Turner, John A.; Deutsch, Todd G.


    Solar water splitting via multi-junction semiconductor photoelectrochemical cells provides direct conversion of solar energy to stored chemical energy as hydrogen bonds. Economical hydrogen production demands high conversion efficiency to reduce balance-of-systems costs. For sufficient photovoltage, water-splitting efficiency is proportional to the device photocurrent, which can be tuned by judicious selection and integration of optimal semiconductor bandgaps. Here, we demonstrate highly efficient, immersed water-splitting electrodes enabled by inverted metamorphic epitaxy and a transparent graded buffer that allows the bandgap of each junction to be independently varied. Voltage losses at the electrolyte interface are reduced by 0.55 V over traditional, uniformly p-doped photocathodes by using a buried p-n junction. Advanced on-sun benchmarking, spectrally corrected and validated with incident photon-to-current efficiency, yields over 16% solar-to-hydrogen efficiency with GaInP/GaInAs tandem absorbers, representing a 60% improvement over the classical, high-efficiency tandem III-V device.

  1. Growth and characterization of insulating ferromagnetic semiconductor (Al,Fe)Sb

    Energy Technology Data Exchange (ETDEWEB)

    Anh, Le Duc, E-mail:; Kaneko, Daiki; Tanaka, Masaaki, E-mail: [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Hai, Pham Nam [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-0033 (Japan)


    We investigate the crystal structure, transport, and magnetic properties of Fe-doped ferromagnetic semiconductor (Al{sub 1−x},Fe{sub x})Sb thin films up to x = 14% grown by molecular beam epitaxy. All the samples show p-type conduction at room temperature and insulating behavior at low temperature. The (Al{sub 1−x},Fe{sub x})Sb thin films with x ≤ 10% maintain the zinc blende crystal structure of the host material AlSb. The (Al{sub 1−x},Fe{sub x})Sb thin film with x = 10% shows intrinsic ferromagnetism with a Curie temperature (T{sub C}) of 40 K. In the (Al{sub 1−x},Fe{sub x})Sb thin film with x = 14%, a sudden drop of the hole mobility and T{sub C} was observed, which may be due to the microscopic phase separation. The observation of ferromagnetism in (Al,Fe)Sb paves the way to realize a spin-filtering tunnel barrier that is compatible with well-established III-V semiconductor devices.

  2. Compound semiconductor alloys: From atomic-scale structure to bandgap bowing

    Energy Technology Data Exchange (ETDEWEB)

    Schnohr, C. S., E-mail: [Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena (Germany)


    Compound semiconductor alloys such as In{sub x}Ga{sub 1−x}As, GaAs{sub x}P{sub 1−x}, or CuIn{sub x}Ga{sub 1−x}Se{sub 2} are increasingly employed in numerous electronic, optoelectronic, and photonic devices due to the possibility of tuning their properties over a wide parameter range simply by adjusting the alloy composition. Interestingly, the material properties are also determined by the atomic-scale structure of the alloys on the subnanometer scale. These local atomic arrangements exhibit a striking deviation from the average crystallographic structure featuring different element-specific bond lengths, pronounced bond angle relaxation and severe atomic displacements. The latter, in particular, have a strong influence on the bandgap energy and give rise to a significant contribution to the experimentally observed bandgap bowing. This article therefore reviews experimental and theoretical studies of the atomic-scale structure of III-V and II-VI zincblende alloys and I-III-VI{sub 2} chalcopyrite alloys and explains the characteristic findings in terms of bond length and bond angle relaxation. Different approaches to describe and predict the bandgap bowing are presented and the correlation with local structural parameters is discussed in detail. The article further highlights both similarities and differences between the cubic zincblende alloys and the more complex chalcopyrite alloys and demonstrates that similar effects can also be expected for other tetrahedrally coordinated semiconductors of the adamantine structural family.

  3. Semiconductor nanostructures in biological applications

    Energy Technology Data Exchange (ETDEWEB)

    Alexson, Dimitri [Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Chen Hongfeng [Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Cho, Michael [Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Department of Physics, University of Illinois at Chicago, Chicago, IL 60607 (United States); Dutta, Mitra [Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Department of Physics, University of Illinois at Chicago, Chicago, IL 60607 (United States); Li Yang [Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Shi, Peng [Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Raichura, Amit [Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Ramadurai, Dinakar [Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Parikh, Shaunak [Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Stroscio, Michael A [Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Department of Physics, University of Illinois at Chicago, Chicago, IL 60607 (United States); Vasudev, Milana [Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607 (United States)


    Semiconductor nanostructures in biological applications are discussed. Results are presented on the use of colloidal semiconductor quantum dots both as biological tags and as structures that interact with and influence biomolecules. Results are presented on the use of semiconducting carbon nanotubes in biological applications. (topical review)

  4. Variable temperature semiconductor film deposition (United States)

    Li, Xiaonan; Sheldon, Peter


    A method of depositing a semiconductor material on a substrate. 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.

  5. Optical coherent control in semiconductors

    DEFF Research Database (Denmark)

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


    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...

  6. II-VI semiconductor compounds

    CERN Document Server


    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.

  7. Semiconductor photocatalysis principles and applications

    CERN Document Server

    Kisch, Horst


    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.

  8. Organic semiconductors in a spin

    CERN Document Server

    Samuel, I


    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.)

  9. Semiconductors for Plasmonics and Metamaterials

    CERN Document Server

    Naik, Gururaj V; 10.1002/pssr.201004269


    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 semiconductors can alleviate these problems if only semiconductors could exhibit negative real permittivity. Aluminum doped zinc oxide (AZO) is a low loss semiconductor that can show negative real permittivity in the NIR. A comparative assessment of AZO-based plasmonic devices such as superlens and hyperlens with their metal-based counterparts shows that AZO-based devices significantly outperform at a wavelength of 1.55 um. This provides a strong stimulus in turning to semiconductor plasmonics at the telecommunication wavelengths.

  10. Binary-Signal Recovery (United States)

    Griebeler, Elmer L.


    Binary communication through long cables, opto-isolators, isolating transformers, or repeaters can become distorted in characteristic ways. The usual solution is to slow the communication rate, change to a different method, or improve the communication media. It would help if the characteristic distortions could be accommodated at the receiving end to ease the communication problem. The distortions come from loss of the high-frequency content, which adds slopes to the transitions from ones to zeroes and zeroes to ones. This weakens the definition of the ones and zeroes in the time domain. The other major distortion is the reduction of low frequency, which causes the voltage that defines the ones or zeroes to drift out of recognizable range. This development describes a method for recovering a binary data stream from a signal that has been subjected to a loss of both higher-frequency content and low-frequency content that is essential to define the difference between ones and zeroes. The method makes use of the frequency structure of the waveform created by the data stream, and then enhances the characteristics related to the data to reconstruct the binary switching pattern. A major issue is simplicity. The approach taken here is to take the first derivative of the signal and then feed it to a hysteresis switch. This is equivalent in practice to using a non-resonant band pass filter feeding a Schmitt trigger. Obviously, the derivative signal needs to be offset to halfway between the thresholds of the hysteresis switch, and amplified so that the derivatives reliably exceed the thresholds. A transition from a zero to a one is the most substantial, fastest plus movement of voltage, and therefore will create the largest plus first derivative pulse. Since the quiet state of the derivative is sitting between the hysteresis thresholds, the plus pulse exceeds the plus threshold, switching the hysteresis switch plus, which re-establishes the data zero to one transition

  11. Massive Black Hole Binary Evolution

    Directory of Open Access Journals (Sweden)

    Merritt David


    Full Text Available Coalescence of binary supermassive black holes (SBHs would constitute the strongest sources of gravitational waves to be observed by LISA. While the formation of binary SBHs during galaxy mergers is almost inevitable, coalescence requires that the separation between binary components first drop by a few orders of magnitude, due presumably to interaction of the binary with stars and gas in a galactic nucleus. This article reviews the observational evidence for binary SBHs and discusses how they would evolve. No completely convincing case of a bound, binary SBH has yet been found, although a handful of systems (e.g. interacting galaxies; remnants of galaxy mergers are now believed to contain two SBHs at projected separations of <~ 1kpc. N-body studies of binary evolution in gas-free galaxies have reached large enough particle numbers to reproduce the slow, “diffusive” refilling of the binary’s loss cone that is believed to characterize binary evolution in real galactic nuclei. While some of the results of these simulations - e.g. the binary hardening rate and eccentricity evolution - are strongly N-dependent, others - e.g. the “damage” inflicted by the binary on the nucleus - are not. Luminous early-type galaxies often exhibit depleted cores with masses of ~ 1-2 times the mass of their nuclear SBHs, consistent with the predictions of the binary model. Studies of the interaction of massive binaries with gas are still in their infancy, although much progress is expected in the near future. Binary coalescence has a large influence on the spins of SBHs, even for mass ratios as extreme as 10:1, and evidence of spin-flips may have been observed.

  12. Visual binary stars: data to investigate formation of binaries (United States)

    Kovaleva,, D.; Malkov,, O.; Yungelson, L.; Chulkov, D.

    Statistics of orbital parameters of binary stars as well as statistics of their physical characteristics bear traces of star formation history. However, statistical investigations of binaries are complicated by incomplete or missing observational data and by a number of observational selection effects. Visual binaries are the most common type of observed binary stars, with the number of pairs exceeding 130 000. The most complete list of presently known visual binary stars was compiled by cross-matching objects and combining data of the three largest catalogues of visual binaries. This list was supplemented by the data on parallaxes, multicolor photometry, and spectral characteristics taken from other catalogues. This allowed us to compensate partly for the lack of observational data for these objects. The combined data allowed us to check the validity of observational values and to investigate statistics of the orbital and physical parameters of visual binaries. Corrections for incompleteness of observational data are discussed. The datasets obtained, together with modern distributions of binary parameters, will be used to reconstruct the initial distributions and parameters of the function of star formation for binary systems.

  13. Hybrid III-V Silicon Lasers (United States)

    Bowers, John


    Abstract: A number of important breakthroughs in the past decade have focused attention on Si as a photonic platform. We review here recent progress in this field, focusing on efforts to make lasers, amplifiers, modulators and photodetectors on or in silicon. We also describe optimum quantum well design and distributed feedback cavity design to reduce the threshold and increase the efficiency and power output. The impact active silicon photonic integrated circuits could have on interconnects, telecommunications and on silicon electronics is reviewed. Biography: John Bowers holds the Fred Kavli Chair in Nanotechnology, and is the Director of the Institute for Energy Efficiency and a Professor in the Departments of Electrical and Computer Engineering and Materials at UCSB. He is a cofounder of Aurrion, Aerius Photonics and Calient Networks. Dr. Bowers received his M.S. and Ph.D. degrees from Stanford University and worked for AT&T Bell Laboratories and Honeywell before joining UC Santa Barbara. Dr. Bowers is a member of the National Academy of Engineering and a fellow of the IEEE, OSA and the American Physical Society. He is a recipient of the OSA/IEEE Tyndall Award, the OSA Holonyak Prize, the IEEE LEOS William Streifer Award and the South Coast Business and Technology Entrepreneur of the Year Award. He and coworkers received the EE Times Annual Creativity in Electronics (ACE) Award for Most Promising Technology for the hybrid silicon laser in 2007. Bowers' research is primarily in optoelectronics and photonic integrated circuits. He has published ten book chapters, 600 journal papers, 900 conference papers and has received 54 patents. He has published 180 invited papers and conference papers, and given 16 plenary talks at conferences. As well as Chong Zhang.

  14. EDITORIAL: Focus on Dilute Magnetic Semiconductors FOCUS ON DILUTE MAGNETIC SEMICONDUCTORS (United States)

    Chambers, Scott A.; Gallagher, Bryan


    This focus issue of New Journal of Physics is devoted to the materials science of dilute magnetic semiconductors (DMS). A DMS is traditionally defined as a diamagnetic semiconductor doped with a few to several atomic per cent of some transition metal with unpaired d electrons. Several kinds of dopant-dopant interactions can in principle couple the dopant spins leading to a ferromagnetic ground state in a dilute magnetic system. These include superexchange, which occurs principally in oxides and only between dopants with one intervening oxygen, and double exchange, in which dopants of different formal charges exchange an electron. In both of these mechanisms, the ferromagnetic alignment is not critically dependent on free carriers in the host semiconductor because exchange occurs via bonds. A third mechanism, discovered in the last few years, involves electrons associated with lattice defects that can apparently couple dopant spins. This mechanism is not well understood. Finally, the most desirable mechanism is carrier-mediated exchange interaction in which the dopant spins are coupled by itinerant electrons or holes in the host semiconductor. This mechanism introduces a fundamental link between magnetic and electrical transport properties and offers the possibility of new spintronic functionalities. In particular electrical gate control of ferromagnetism and the use of spin polarized currents to carry signals for analog and digital applications. The spin light emitting diode is a prototypical device of this kind that has been extensively used to characterize the extent of spin polarization in the active light emitting semiconductor heterostructure. The prototypical carrier mediated ferromagnetic DMS is Mn-doped GaAs. This and closely related narrow gap III-V materials have been very extensively studied. Their properties are generally quite well understood and they have led to important insights into fundamental properties of ferromagnetic systems with strong spin

  15. Semiconductor nanowire lasers (United States)

    Eaton, Samuel W.; Fu, Anthony; Wong, Andrew B.; Ning, Cun-Zheng; Yang, Peidong


    The discovery and continued development of the laser has revolutionized both science and industry. The advent of miniaturized, semiconductor lasers has made this technology an integral part of everyday life. Exciting research continues with a new focus on nanowire lasers because of their great potential in the field of optoelectronics. In this Review, we explore the latest advancements in the development of nanowire lasers and offer our perspective on future improvements and trends. We discuss fundamental material considerations and the latest, most effective materials for nanowire lasers. A discussion of novel cavity designs and amplification methods is followed by some of the latest work on surface plasmon polariton nanowire lasers. Finally, exciting new reports of electrically pumped nanowire lasers with the potential for integrated optoelectronic applications are described.

  16. 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


    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.

  17. A semiconductor based electrode

    Energy Technology Data Exchange (ETDEWEB)

    Khamatani, A.; Kobayasi, K.


    The semiconductor electrode is submerged into an electrolyte which is held in the illuminated chamber. The other electrode is placed in a dark chamber connected with the channel to be illuminated, which has a partition in the form of a membrane. An electric current flows in the external circuit of the element with illumination of the first electrode. The illuminated electrode is covered with a thin film of a substance which is stable with the action of the electrolyte. The film is made of Si02, A1203, GaN or A1N. The protective coating makes it possible to use materials less stable than Ti02 in a rutile modification, but which have higher characteristics than the GaP, GaAs, CdS and InP, for making the electrode.

  18. EDITORIAL: Non-polar and semipolar nitride semiconductors Non-polar and semipolar nitride semiconductors (United States)

    Han, Jung; Kneissl, Michael


    -nitride-based laser diodes is compared. Leung et al discuss the optical emission characteristics of semipolar (1122) GaN light-emitting diodes on m-sapphire and stripe-etched r-sapphire, and Jung et al present results on high brightness non-polar a-plane GaN light-emitting diodes. Finally, in a review Konar et al discuss the charge transport in non- and semipolar III-V nitride heterostructures, and Ishida et al present the latest results on non-polar AlGaN/GaN HFETs with a normally-off operation. Overall, we think that this special issue of Semiconductor Science and Technology provides a comprehensive overview of the state-of-the-art in the field on non-polar and semipolar nitride materials and devices. In view of the rapidly growing interest in this field, the demonstrated enhanced device performance and the wide range of applications, this special issue can be considered a very timely contribution. Finally, we would like to thank the IOP editorial staff, in particular Jarlath McKenna, for their support, and we would also like to thank all contributors for their efforts in making this special issue possible.

  19. Biomolecule-directed assembly of binary gold and titanium dioxide nanoparticles. (United States)

    Zhu, Xiaoli; Chen, Zhenyu; Zhang, Xin; Zhu, Zhiqiang; Li, Genxi


    We report in this paper a novel strategy for "bottom-up" assembly of two types of metallic and semiconductor nanoparticles. By only using a small biomolecule, coenzyme A, as a "linker" to direct the assembly of metallic gold and semiconductor titanium dioxide nanoparticles, the usual biomolecule-directed system can be greatly simplified. Effects of experimental conditions on the formation of binary nanoparticles are studied. This strategy using single small biomolecule to direct assembly of nanoparticles is proven to be efficient, facile and non-toxic and should be extendable to other building blocks.

  20. Modifying the emission of light from a semiconductor nanowire array (United States)

    Anttu, Nicklas


    Semiconductor nanowire arrays have been identified as a promising platform for future light emitting diodes (LEDs), for example, due to the materials science freedom of combining lattice-mismatched materials in them. Furthermore, the emission of light from nanowires can be tailored by designing their geometry. Such tailoring could optimize the emission of light to the top side as well as enhance the emission rate through the Purcell effect. However, the possibility for enhanced light extraction from III-V nanowire arrays over a conventional bulk-like LED has not been investigated systematically. Here, we use electromagnetic modeling to study the emission of light from nanowire arrays. We vary both the diameter of the nanowires and the array period to show the benefit of moving from a bulk-like LED to a nanowire array LED. We study the fraction of light emitted to the top air side and to the substrate at wavelength λ. We find several diameter-dependent resonant peaks for which the emission to the top side is maximized. For the strongest such peak, by increasing the array period, the fraction of emitted light that is extracted at the top air side can be enhanced by a factor of 30 compared to that in a planar bulk LED. By modeling a single nanowire, we confirm that it is beneficial to place the nanowires further apart to enhance the emission to the top side. Furthermore, we predict that for a nanowire diameter D > λ/2, a majority of the emitted power ends up in the substrate. Our results offer direction for the design and optimization of nanowire-array based light emitting diodes.

  1. Adsorption properties of CdS-CdTe system semiconductors (United States)

    Kirovskaya, I. A.; Nor, P. E.


    The adsorption of carbon(II) oxide and ammonia on nanofilms of solid solutions and binary compounds of the CdS-CdTe system is studied by means of piezoquartz microweighing, FTIR IR, and measuring electroconductivity. Allowing for the conditions and composition of semiconductor systems, we determine the mechanisms and principles of adsorption processes by analyzing the α p = f( T), α T = f( p), and α T = f( t) experimental dependences; IR spectra; the thermodynamic and kinetic characteristics of adsorption; the acid-base, electrophysical, and other characteristics of adsorbents; the electron nature of adsorbate molecules; and the obtained acid-base characteristics: the composition and adsorption characteristics and composition state diagrams. Previous statements on the nature and retention of local active centers responsible for adsorption and catalytic processes upon changes in their habitus and composition (as components of systems of the AIIIBV-AIIBVI and AIIBVI-AIIBVI types) on the surface of diamond-like semiconductors are confirmed. Specific features of the behavior of (CdS) x (CdTe)1 - x solid solutions are identified in addition to general features with binary compounds (CdS, CdTe), as is demonstrated by the presence of critical points on acid-base characteristics-composition and adsorption characteristics-composition diagrams. On the basis of these diagrams, the most active adsorbents (with respect to CO and NH3) used in designing highly sensitive and selective sensors are identified.

  2. Rotational mixing in close binaries

    CERN Document Server

    de Mink, S E; Langer, N; Yoon, S -Ch; Brott, I; Glebbeek, E; Verkoulen, M; Pols, O R


    Rotational mixing is a very important but uncertain process in the evolution of massive stars. We propose to use close binaries to test its efficiency. Based on rotating single stellar models we predict nitrogen surface enhancements for tidally locked binaries. Furthermore we demonstrate the possibility of a new evolutionary scenario for very massive (M > 40 solar mass) close (P < 3 days) binaries: Case M, in which mixing is so efficient that the stars evolve quasi-chemically homogeneously, stay compact and avoid any Roche-lobe overflow, leading to very close (double) WR binaries.

  3. Evolution of Close Binary Systems

    Energy Technology Data Exchange (ETDEWEB)

    Yakut, K; Eggleton, P


    We collected data on the masses, radii, etc. of three classes of close binary stars: low-temperature contact binaries (LTCBs), near-contact binaries (NCBs), and detached close binaries (DCBs). They restrict themselves to systems where (1) both components are, at least arguably, near the Main Sequence, (2) the periods are less than a day, and (3) there is both spectroscopic and photometric analysis leading to reasonably reliable data. They discuss the possible evolutionary connections between these three classes, emphasizing the roles played by mass loss and angular momentum loss in rapidly-rotating cool stars.

  4. Chaos in Binary Category Computation

    CERN Document Server

    Gonçalves, Carlos Pedro


    Category computation theory deals with a web-based systemic processing that underlies the morphic webs, which constitute the basis of categorial logical calculus. It is proven that, for these structures, algorithmically incompressible binary patterns can be morphically compressed, with respect to the local connectivities, in a binary morphic program. From the local connectivites, there emerges a global morphic connection that can be characterized by a low length binary string, leading to the identification of chaotic categorial dynamics, underlying the algorithmically random pattern. The work focuses on infinite binary chains of C2, which is a category that implements an X-OR-based categorial logical calculus.

  5. Low autocorrelation binary sequences (United States)

    Packebusch, Tom; Mertens, Stephan


    Binary sequences with minimal autocorrelations have applications in communication engineering, mathematics and computer science. In statistical physics they appear as groundstates of the Bernasconi model. Finding these sequences is a notoriously hard problem, that so far can be solved only by exhaustive search. We review recent algorithms and present a new algorithm that finds optimal sequences of length N in time O(N {1.73}N). We computed all optimal sequences for N≤slant 66 and all optimal skewsymmetric sequences for N≤slant 119.

  6. Microlensing modulation by binaries

    CERN Document Server

    Dubath, F; Durrer, R; Dubath, Florian; Gasparini, Maria Alice; Durrer, Ruth


    We compute the effect of the lens quadrupole on microlensing. The time dependence of the quadrupole can lead to specific modulations of the amplification signal. We study especially binary system lenses in our galaxy. The modulation is observable if the rotation period of the system is smaller than the time over which the amplification is significant and if the impact parameter of the passing light ray is sufficiently close to the Einstein radius so that the amplification is very large. Observations of this modulation can reveal important information on the quadrupole and thus on the gravitational radiation emitted by the lens.

  7. Semiconductor Nanocrystals for Biological Imaging

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

  8. Li(Zn,Co,MnAs: A bulk form diluted magnetic semiconductor with Co and Mn co-doping at Zn sites

    Directory of Open Access Journals (Sweden)

    Bijuan Chen


    Full Text Available We report the synthesis and characterization of a series of bulk forms of diluted magnetic semiconductors Li(Zn1-x-yCoxMnyAs with a crystal structure close to that of III-V diluted magnetic semiconductor (Ga,MnAs. No ferromagnetic order occurs with single (Zn,Co or (Zn, Mn substitution in the parent compound LiZnAs. Only with co-doped Co and Mn ferromagnetic ordering can occur at the Curie temperature ∼40 K. The maximum saturation moment of the this system reached to 2.17μB/Mn, which is comparable to that of Li (Zn,MnAs. It is the first time that a diluted magnetic semiconductor with co-doping Co and Mn into Zn sites is achieved in “111” LiZnAs system, which could be utilized to investigate the basic science of ferromagnetism in diluted magnetic semiconductors. In addition, ferromagnetic Li(Zn,Co,MnAs, antiferromagnetic LiMnAs, and superconducting LiFeAs share square lattice at As layers, which may enable the development of novel heterojunction devices in the future.

  9. Li(Zn,Co,Mn)As: A bulk form diluted magnetic semiconductor with Co and Mn co-doping at Zn sites (United States)

    Chen, Bijuan; Deng, Zheng; Li, Wenmin; Gao, Moran; Zhao, Jianfa; Zhao, Guoqiang; Yu, Shuang; Wang, Xiancheng; Liu, Qingqing; Jin, Changqing


    We report the synthesis and characterization of a series of bulk forms of diluted magnetic semiconductors Li(Zn1-x-yCoxMny)As with a crystal structure close to that of III-V diluted magnetic semiconductor (Ga,Mn)As. No ferromagnetic order occurs with single (Zn,Co) or (Zn, Mn) substitution in the parent compound LiZnAs. Only with co-doped Co and Mn ferromagnetic ordering can occur at the Curie temperature ˜40 K. The maximum saturation moment of the this system reached to 2.17 μB /Mn , which is comparable to that of Li (Zn,Mn)As. It is the first time that a diluted magnetic semiconductor with co-doping Co and Mn into Zn sites is achieved in "111" LiZnAs system, which could be utilized to investigate the basic science of ferromagnetism in diluted magnetic semiconductors. In addition, ferromagnetic Li(Zn,Co,Mn)As, antiferromagnetic LiMnAs, and superconducting LiFeAs share square lattice at As layers, which may enable the development of novel heterojunction devices in the future.

  10. Semiconductor device PN junction fabrication using optical processing of amorphous semiconductor material (United States)

    Sopori, Bhushan; Rangappan, Anikara


    Systems and methods for semiconductor device PN junction fabrication are provided. In one embodiment, a method for fabricating an electrical device having a P-N junction comprises: depositing a layer of amorphous semiconductor material onto a crystalline semiconductor base, wherein the crystalline semiconductor base comprises a crystalline phase of a same semiconductor as the amorphous layer; and growing the layer of amorphous semiconductor material into a layer of crystalline semiconductor material that is epitaxially matched to the lattice structure of the crystalline semiconductor base by applying an optical energy that penetrates at least the amorphous semiconductor material.

  11. Quantum optics with semiconductor nanostructures

    CERN Document Server

    Jahnke, Frank


    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...

  12. Semiconductor nanoparticles for quantum devices (United States)

    Erokhin, Victor; Carrara, Sandro; Amenitch, H.; Bernstorff, S.; Nicolini, Claudio


    Semiconductor nanoparticles were synthesized by exposing fatty acid salt Langmuir-Blodgett films to the atmosphere of 0957-4484/9/3/004/img8. The particle sizes were characterized by small-angle x-ray scattering of their solutions using synchrotron radiation source at higher resolution, as it was impossible previously to study it with usual laboratory x-ray sources. The particle sizes were found to correspond with the demands of single-electron and quantum junctions. Semiconductor heterostructures were grown by self-aggregation of these particles of different types. Electrical properties of these nanostructures were studied by using STM. Voltage-current characteristics revealed the presence of differential negative resistance. Measurements confirmed the formation of semiconductor superlattices directed towards a development of new nanodevices, such as tunnelling diodes and semiconductor lasers.

  13. Multinary wurtzite-type oxide semiconductors: present status and perspectives (United States)

    Suzuki, Issei; Omata, Takahisa


    Oxide-based optoelectronic devices have been limited in applicable wavelength to the near-UV region because there are few viable binary wurtzite-type oxides, but ternary wurtzite-type (β-NaFeO2-type) oxides are promising materials to expand the applicable wavelengths of these devices. In the past decade, many attractive properties of β-NaFeO2-type oxide semiconductors have been revealed, such as the band-engineering of ZnO by alloying with β-LiGaO2 and β-AgGaO2, the photocatalytic activities of β-AgGaO2 and β-AgAlO2, and the discovery that β-CuGaO2 is suitable for thin-film solar-cell absorbers. In this review article, we consider previous studies of β-NaFeO2-type oxide semiconductors—β-LiGaO2, β-AgGaO2, β-AgAlO2, β-CuGaO2—and their alloys with ZnO, and discuss their structural features, optical and electrical properties, and the relationship between their crystal structures and electronic band structures. We describe the outlook of β-NaFeO2-type oxide semiconductors and the remaining issues that hinder the development of optoelectronic devices made from β-NaFeO2-type oxide semiconductors.

  14. Semiconductor packaging materials interaction and reliability

    CERN Document Server

    Chen, Andrea


    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

  15. Optical Orientation in Ferromagnet/Semiconductor Hybrids


    Korenev, V. L.


    The physics of optical pumping of semiconductor electrons in the ferromagnet/semiconductor hybrids is discussed. Optically oriented semiconductor electrons detect the magnetic state of the ferromagnetic film. In turn, the ferromagnetism of the hybrid can be controlled optically with the help of the semiconductor. Spin-spin interactions near the interface ferromagnet/semiconductor play crucial role in the optical readout and the manipulation of ferromagnetism.

  16. The C-terminal N-glycosylation sites of the human alpha1,3/4-fucosyltransferase III, -V, and -VI (hFucTIII, -V, adn -VI) are necessary for the expression of full enzyme activity. (United States)

    Christensen, L L; Jensen, U B; Bross, P; Orntoft, T F


    The alpha1,3/4-fucosyltransferases are involved in the synthesis of fucosylated cell surface glycoconjugates. Human alpha1,3/4-fucosyltransferase III, -V, and -VI (hFucTIII, -V, and -VI) contain two conserved C-terminal N-glycosylation sites (hFucTIII: Asn154 and Asn185; hFucTV: Asn167 and Asn198; and hFucTVI: Asn153 and Asn184). In the present study, we have analyzed the functional role of these potential N-glycosylation sites, laying the main emphasis on the sites in hFucTIII. Tunicamycin treatment completely abolished hFucTIII enzyme activity while castanospermine treatment diminished hFucTIII enzyme activity to approximately 40% of the activity of the native enzyme. To further analyze the role of the conserved N-glycosylation sites in hFucTIII, -V, and -VI, we made a series of mutant genomic DNAs in which the asparagine residues in the potential C-terminal N-glycosylation sites were replaced by glutamine. Subsequently, the hFucTIII, -V, and -VI wild type and the mutants were expressed in COS-7 cells. All the mutants exhibited lower enzyme activity than the wild type and elimination of individual sites had different effects on the activity. The mutations did not affect the protein level of the mutants in the cells, but reduced the molecular mass as predicted. Kinetic analysis of hFucTIII revealed that lack of glycosylation at Asn185 did not change the Km values for the oligosaccharide acceptor and the nucleotide sugar donor. The present study demonstrates that hFucTIII, -V, and -VI require N-glycosylation at the two conserved C-terminal N-glycosylation sites for expression of full enzyme activity.

  17. Evolution of Binaries in Dense Stellar Systems

    CERN Document Server

    Ivanova, Natalia


    In contrast to the field, the binaries in dense stellar systems are frequently not primordial, and could be either dynamically formed or significantly altered from their primordial states. Destruction and formation of binaries occur in parallel all the time. The destruction, which constantly removes soft binaries from a binary pool, works as an energy sink and could be a reason for cluster entering the binary-burning phase. The true binary fraction is greater than observed, as a result, the observable binary fraction evolves differently from the predictions. Combined measurements of binary fractions in globular clusters suggest that most of the clusters are still core-contracting. The formation, on other hand, affects most the more evolutionary advanced stars, which significantly enhances the population of X-ray sources in globular clusters. The formation of binaries with a compact objects proceeds mainly through physical collisions, binary-binary and single-binary encounters; however, it is the dynamical for...

  18. 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:


    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.

  19. Seebeck effect in polycrystalline semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Jerhot, J.; Vlcek, J.


    The paper deals with the interpretation of the Seebeck coefficient measured for a polycrystalline semiconductor. Polycrystalline semiconductors are considered to be composed of grains separated from one another by intergrain domains. An isotype heterojunction with a certain density of interface states is assumed to exist at the grain-intergrain domain interface. The general formula for the Seebeck coefficient under these conditions is derived. The relations valid for systems of practical interest are shown as limiting cases of the formula presented.

  20. Semiconductor crystal high resolution imager (United States)

    Levin, Craig S. (Inventor); Matteson, James (Inventor)


    A radiation imaging device (10). The radiation image device (10) comprises a subject radiation station (12) producing photon emissions (14), and at least one semiconductor crystal detector (16) arranged in an edge-on orientation with respect to the emitted photons (14) to directly receive the emitted photons (14) and produce a signal. The semiconductor crystal detector (16) comprises at least one anode and at least one cathode that produces the signal in response to the emitted photons (14).

  1. A semiconductor laser excitation circuit

    Energy Technology Data Exchange (ETDEWEB)

    Kaadzunari, O.; Masaty, K.


    A semiconductor laser excitation circuit is patented that is designed for operation in a pulsed mode with a high pulse repetition frequency. This circuit includes, in addition to a semiconductor laser, a high speed photodetector, a reference voltage source, a comparator, and a pulse oscillator and modulator. If the circuit is built using standard silicon integrated circuits, its speed amounts to several hundred megahertz, if it is constructed using gallium arsenide integrated circuits, its speed is several gigahertz.

  2. Spin Correlation in Binary Systems

    CERN Document Server

    Farbiash, N; Farbiash, Netzach; Steinitz, Raphael


    We examine the correlation of projected rotational velocities in binary systems. It is an extension of previous work (Steinitz and Pyper, 1970; Levato, 1974). An enlarged data basis and new tests enable us to conclude that there is indeed correlation between the projected rotational velocities of components of binaries. In fact we suggest that spins are already correlated.

  3. Evolutionary Memory in Binary Systems?

    CERN Document Server

    Steinitz, N F R


    Correlation between the spins (rotational velocities) in binaries has previously been established. We now continue and show that the degree of spin correlation is independent of the components' separation. Such a result might be related for example to Zhang's non-linear model for the formation of binary stars from a nebula.

  4. Relativistic Binaries in Globular Clusters

    Directory of Open Access Journals (Sweden)

    Matthew J. Benacquista


    Full Text Available Galactic globular clusters are old, dense star systems typically containing 10^4 – 10^6 stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of tight binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct N-body integrations and Fokker–Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.


    Institute of Scientific and Technical Information of China (English)

    XuChengqian; ZhaoXiaoqun


    A new set of binary sequences-Periodic Complementary Binary Sequence Pair (PCSP)is proposed .A new class of block design-Difference Family Pair (DFP)is also proposed .The relationship between PCSP and DFP,the properties and exising conditions of PCSP and the recursive constructions for PCSP are given.


    Institute of Scientific and Technical Information of China (English)

    Xu Chengqian; Zhao Xiaoqun


    A new set of binary sequences-Periodic Complementary Binary Sequence Pair (PCSP) is proposed. A new class of block design-Difference Family Pair (DFP) is also proposed.The relationship between PCSP and DFP, the properties and existing conditions of PCSP and the recursive constructions for PCSP are given.

  7. Relativistic Binaries in Globular Clusters

    Directory of Open Access Journals (Sweden)

    Benacquista Matthew J.


    Full Text Available The galactic population of globular clusters are old, dense star systems, with a typical cluster containing 10^4 - 10^7 stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss the theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution which lead to relativistic binaries, and current and possible future observational evidence for this population. Globular cluster evolution will focus on the properties that boost the production of hard binary systems and on the tidal interactions of the galaxy with the cluster, which tend to alter the structure of the globular cluster with time. The interaction of the components of hard binary systems alters the evolution of both bodies and can lead to exotic objects. Direct N-body integrations and Fokker-Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.

  8. Relativistic Binaries in Globular Clusters

    Directory of Open Access Journals (Sweden)

    Benacquista Matthew


    Full Text Available The galactic population of globular clusters are old, dense star systems, with a typical cluster containing $10^4 - 10^6$ stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss the theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution which lead to relativistic binaries, and current and possible future observational evidence for this population. Globular cluster evolution will focus on the properties that boost the production of hard binary systems and on the tidal interactions of the galaxy with the cluster, which tend to alter the structure of the globular cluster with time. The interaction of the components of hard binary systems alters the evolution of both bodies and can lead to exotic objects. Direct $N$-body integrations and Fokker--Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.

  9. The ATLAS Semiconductor tracker: operations and performance

    CERN Document Server

    Pani, P; The ATLAS collaboration


    Tracker After more than 3 years of successful operation at the LHC, we report on the operation and performance of the Semi-Conductor Tracker (SCT) functioning in a high luminosity, high radiation environment. The SCT is part of the ATLAS experiment at CERN and is constructed of 4088 silicon detector modules for a total of 6.3 million strips. Each module is designed, constructed and tested to operate as a stand-alone unit, mechanically, electrically, optically and thermally. The modules are mounted into two types of structures: one barrel (4 cylinders) and two end-cap systems (9 disks on each end of the barrel). The SCT silicon micro-strip sensors are processed in the planar p-in-n technology. The signals are processed in the front-end ABCD3TA ASICs, which use a binary readout architecture. Data is transferred to the off-detector readout electronics via optical fibers. We find 99.3% of the SCT modules are operational, noise occupancy and hit efficiency exceed the design specifications; the alignment is very cl...

  10. Semiconductors for plasmonics and metamaterials

    DEFF Research Database (Denmark)

    Naik, G.V.; Boltasseva, Alexandra


    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......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 semiconductors can alleviate these problems if only semiconductors could exhibit negative real permittivity. Aluminum doped zinc oxide (AZO) is a low loss semiconductor that can show negative real permittivity in the NIR. A comparative assessment of AZO-based plasmonic devices such as superlens and hyperlens...... with their metal-based counterparts shows that AZO-based devices significantly outperform at a wavelength of 1.55 µm. This provides a strong stimulus in turning to semiconductor plasmonics at the telecommunication wavelengths. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)....

  11. Survey of cryogenic semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

  12. A semiconductor laser

    Energy Technology Data Exchange (ETDEWEB)

    Naoko, O.; Khiroiti, S.


    An improved method is patented for increasing the service life of semiconductor lasers which does not hinder their characteristics, by applying a protective film to the end planes of the optical resonator of the laser. It is recommended that a mixture of an A1203 dielectric and an inert element such as argon be used for a GaAs, GaA1As laser as the protective film. The radii of gallium and arsenic atoms are equal to 1.24 and 1.25 angstroms, respectively. The radii of A1, O and Si atoms which make up the protective film are equal to 1.43, .61 and 1.17 angstroms, respectively. The radius of the argon atoms in the protective film, which is equal to 1.91 angstroms) is high compared to the atoms noted above. As a result, the movement of the gallium and arsenic atoms, which causes a drop in later characteristics during operation, is made more difficult.

  13. Signature Visualization of Software Binaries

    Energy Technology Data Exchange (ETDEWEB)

    Panas, T


    In this paper we present work on the visualization of software binaries. In particular, we utilize ROSE, an open source compiler infrastructure, to pre-process software binaries, and we apply a landscape metaphor to visualize the signature of each binary (malware). We define the signature of a binary as a metric-based layout of the functions contained in the binary. In our initial experiment, we visualize the signatures of a series of computer worms that all originate from the same line. These visualizations are useful for a number of reasons. First, the images reveal how the archetype has evolved over a series of versions of one worm. Second, one can see the distinct changes between version. This allows the viewer to form conclusions about the development cycle of a particular worm.

  14. Observing binary inspiral with LIGO

    CERN Document Server

    Finn, L S


    Gravitational radiation from a binary neutron star or black hole system leads to orbital decay and the eventual coalescence of the binary's components. During the last several minutes before the binary components coalesce, the radiation will enter the bandwidth of the United States Laser Inteferometer Gravitational-wave Observatory (LIGO) and the French/Italian VIRGO gravitational radiation detector. The combination of detector sensitivity, signal strength, and source density and distribution all point to binary inspiral as the most likely candidate for observation among all the anticipated sources of gravitational radiation for LIGO/VIRGO. Here I review briefly some of the questions that are posed to theorists by the impending observation of binary inspiral.

  15. EDITORIAL: Oxide semiconductors (United States)

    Kawasaki, M.; Makino, T.


    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

  16. 75 FR 49526 - Freescale Semiconductor, Inc., Technical Information Center, Tempe, AZ; Freescale Semiconductor... (United States)


    ... Employment and Training Administration Freescale Semiconductor, Inc., Technical Information Center, Tempe, AZ; Freescale Semiconductor, Inc., Technical Information Center, Woburn, MA; Amended Certification Regarding... Semiconductor, Inc., Technical Information Center, Tempe, Arizona. The notice was published in the...

  17. Towards Physarum Binary Adders

    CERN Document Server

    Jones, Jeff; 10.1016/j.biosystems.2010.04.005


    Plasmodium of \\emph{Physarum polycephalum} is a single cell visible by unaided eye. The plasmodium's foraging behaviour is interpreted in terms of computation. Input data is a configuration of nutrients, result of computation is a network of plasmodium's cytoplasmic tubes spanning sources of nutrients. Tsuda et al (2004) experimentally demonstrated that basic logical gates can be implemented in foraging behaviour of the plasmodium. We simplify the original designs of the gates and show --- in computer models --- that the plasmodium is capable for computation of two-input two-output gate $ \\to $ and three-input two-output $ \\to $. We assemble the gates in a binary one-bit adder and demonstrate validity of the design using computer simulation.

  18. Towards Physarum binary adders. (United States)

    Jones, Jeff; Adamatzky, Andrew


    Plasmodium of Physarum polycephalum is a single cell visible by unaided eye. The plasmodium's foraging behaviour is interpreted in terms of computation. Input data is a configuration of nutrients, result of computation is a network of plasmodium's cytoplasmic tubes spanning sources of nutrients. Tsuda et al. (2004) experimentally demonstrated that basic logical gates can be implemented in foraging behaviour of the plasmodium. We simplify the original designs of the gates and show - in computer models - that the plasmodium is capable for computation of two-input two-output gate x, y-->xy, x+y and three-input two-output x,y,z-->x yz,x+y+z. We assemble the gates in a binary one-bit adder and demonstrate validity of the design using computer simulation.

  19. Eccentric Binary Millisecond Pulsars

    CERN Document Server

    Freire, Paulo C C


    In this paper we review the recent discovery of several millisecond pulsars (MSPs) in eccentric binary systems. Timing these MSPs we were able to estimate (and in one case precisely measure) their masses. These results suggest that, as a class, MSPs have a much wider range of masses (1.3 to > 2 solar masses) than the normal and mildly recycled pulsars found in double neutron star (DNS) systems (1.25 < Mp < 1.44 solar masses). This is very likely to be due to the prolonged accretion episode that is thought to be required to form a MSP. The likely existence of massive MSPs makes them a powerful probe for understanding the behavior of matter at densities larger than that of the atomic nucleus; in particular, the precise measurement of the mass of PSR J1903+0327 ($1.67 +/- 0.01 solar masses) excludes several "soft" equations of state for dense matter.

  20. Temperature dependence of frequency dispersion in III–V metal-oxide-semiconductor C-V and the capture/emission process of border traps

    Energy Technology Data Exchange (ETDEWEB)

    Vais, Abhitosh, E-mail:; Martens, Koen; DeMeyer, Kristin [Department of Electrical Engineering, KU Leuven, B-3000 Leuven (Belgium); IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Lin, Han-Chung; Ivanov, Tsvetan; Collaert, Nadine; Thean, Aaron [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Dou, Chunmeng [Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Xie, Qi; Maes, Jan [ASM International, B-3001 Leuven (Belgium); Tang, Fu; Givens, Michael [ASM International, Phoenix, Arizona 85034-7200 (United States); Raskin, Jean-Pierre [Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Universiteé Catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium)


    This paper presents a detailed investigation of the temperature dependence of frequency dispersion observed in capacitance-voltage (C-V) measurements of III-V metal-oxide-semiconductor (MOS) devices. The dispersion in the accumulation region of the capacitance data is found to change from 4%–9% (per decade frequency) to ∼0% when the temperature is reduced from 300 K to 4 K in a wide range of MOS capacitors with different gate dielectrics and III-V substrates. We show that such significant temperature dependence of C-V frequency dispersion cannot be due to the temperature dependence of channel electrostatics, i.e., carrier density and surface potential. We also show that the temperature dependence of frequency dispersion, and hence, the capture/emission process of border traps can be modeled by a combination of tunneling and a “temperature-activated” process described by a non-radiative multi-phonon model, instead of a widely believed single-step elastic tunneling process.

  1. Spatial light modulation in compound semiconductor materials (United States)

    Cheng, Li-Jen (Inventor); Gheen, Gregory O. (Inventor); Partovi, Afshin (Inventor)


    Spatial light modulation (22) in a III-V single crystal (12), e.g., gallium arsenide, is achieved using the photorefractive effect. Polarization rotation created by beam coupling is utilized in one embodiment. In particular, information (16)on a control beam (14) incident on the crystal is transferred to an input beam (10), also incident on the crystal. An output beam (18) modulated in intensity is obtained by passing the polarization-modulated input beam through a polarizer (20).

  2. Wide-Bandgap Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Chinthavali, M.S.


    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

  3. Dielectric screening in semiconductors (United States)

    Harrison, Walter A.; Klepeis, John E.


    Intra-atomic and interatomic Coulomb interactions are incorporated into bond-orbital theory, based upon universal tight-binding parameters, in order to treat the effects of charge redistribution in semiconductor bonds. The dielectric function ɛ(q) is obtained for wave numbers in a [100] direction. The screening of differences in average hybrid energy across a heterojunction is calculated in detail, indicating that the decay length for the potential depends upon the relative values of Madelung and intra-atomic Coulomb terms. The parameters used here predict an imaginary decay length and thus an oscillating potential near the interface. The same theory is applied to point defects by imbedding a cluster in a matrix lattice, taking charges in that lattice to be consistent with continuum theory. Illustrating the theory with a phosphorus impurity in silicon, it is seen that the impurity and its neighboring atoms have charges on the order of only one-tenth of an electronic charge, alternating in sign from neighbor to neighbor as for planar defects. Although there are shifts in the term values on the order of a volt, the difference in these shifts for neighboring atoms is much smaller so that the effect on the bonds is quite small. This behavior is analogous to the response of a dielectric continuum to a point charge: The medium is locally neutral except at the center of the cluster and there are slowly varying potentials e2/ɛr. Because of this slow variation, free-atom term values should ordinarily suffice for the calculation of bond properties and bond lengths at impurities. Corrections are larger for homovalent substitutions such as carbon in silicon.

  4. Dynamical Evolution of Wide Binaries

    Directory of Open Access Journals (Sweden)

    Esmeralda H. Mallada


    Full Text Available We simulate numerically encounters of wide binaries with field stars and Giant Molecular Clouds (GMCs by means of the impulse approximation. We analyze the time evolution of the distributions of eccentricities and semimajor axes of wide binaries with given initial conditions, at intervals of 109 yr, up to 1010 yr (assumed age of the Galaxy. We compute the fraction of surviving binaries for stellar encounters, for GMC encounters and for a combination of both, and hence, the dynamical lifetime for different semimajor axes and different masses of binaries (0.5, 1, 1.2, 1.5, 2.5, and 3 Msolar. We find that the dynamical lifetime of wide binaries considering only GMCs is half than that considering only stars. For encounters with GMCs we analyze the influence of the initial inclination of the orbital plane of the binary with respect to the plane perpendicular to the relative velocity vector of the binary and the GMC. We find that the perturbation is maximum when the angle is minimum.

  5. Defect-Rich Dopant-Free ZrO2 Nanostructures with Superior Dilute Ferromagnetic Semiconductor Properties. (United States)

    Rahman, Md Anisur; Rout, S; Thomas, Joseph P; McGillivray, Donald; Leung, Kam Tong


    Control of the spin degree of freedom of an electron has brought about a new era in spin-based applications, particularly spin-based electronics, with the potential to outperform the traditional charge-based semiconductor technology for data storage and information processing. However, the realization of functional spin-based devices for information processing remains elusive due to several fundamental challenges such as the low Curie temperature of group III-V and II-VI semiconductors (semiconductors in a multilayer device structure, which are caused by precipitation and migration of dopants from the host layer to the adjacent layers. Here, we use catalyst-assisted pulsed laser deposition to grow, for the first time, oxygen vacancy defect-rich, dopant-free ZrO2 nanostructures with high TC (700 K) and high magnetization (5.9 emu/g). The observed magnetization is significantly greater than both doped and defect-rich transparent conductive oxide nanomaterials reported to date. We also provide the first experimental evidence that it is the amounts and types of oxygen vacancy defects in, and not the phase of ZrO2 that control the ferromagnetic order in undoped ZrO2 nanostructures. To explain the origin of ferromagnetism in these ZrO2 nanostructures, we hypothesize a new defect-induced bound polaron model, which is generally applicable to other defect-rich, dopant-free transparent conductive oxide nanostructures. These results provide new insights into magnetic ordering in undoped dilute ferromagnetic semiconductor oxides and contribute to the design of exotic magnetic and novel multifunctional materials.

  6. Chaotic zones around gravitating binaries

    CERN Document Server

    Shevchenko, Ivan I


    The extent of the continuous zone of chaotic orbits of a small-mass tertiary around a system of two gravitationally bound bodies (a double star, a double black hole, a binary asteroid, etc.) is estimated analytically, in function of the tertiary's orbital eccentricity. The separatrix map theory is used to demonstrate that the central continuous chaos zone emerges due to overlapping of the orbital resonances corresponding to the integer ratios p:1 between the tertiary and the binary periods. The binary's mass ratio, above which such a chaotic zone is universally present, is also estimated.

  7. Semiconductors for solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, H.J. (Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering)


    This review covers the historical background of the solar cell development, the physical principles of photovoltaic energy conversion, technology of solar cell devices and the structural and physical properties of lattice defects in semiconductors. Single crystal and polycrystalline silicon, single crystal and epitaxial gallium arsenide, polycrystalline thin films and amorphous thin films are discussed in detail. Semiconductors have emerged as the most promising group of materials which can convert sunlight directly into electrical energy. They utilize the fundamental physical process that a photon that penetrates into the semiconductor and is absorbed can generate electron-hole pairs. Because of their opposite charges they can be separated by an internal electrical field and collected at two contacts thus giving rise to a voltage and photocurrent if the two contacts are connected externally. In semiconductors internal electric fields occur in connection with space charges at junctions and a variety of technological concepts are used to produce a built-in voltage. The most widely used device principle is the operation of a solar cell as a diode or p-n junction. Alternative concepts are heterojunction devices where the materials on either side of the junction are different semiconductors. (author).

  8. Modified evolution of stellar binaries from supermassive black hole binaries (United States)

    Liu, Bin; Wang, Yi-Han; Yuan, Ye-Fei


    The evolution of main-sequence binaries resided in the galactic centre is influenced a lot by the central supermassive black hole (SMBH). Due to this perturbation, the stars in a dense environment are likely to experience mergers or collisions through secular or non-secular interactions. In this work, we study the dynamics of the stellar binaries at galactic centre, perturbed by another distant SMBH. Geometrically, such a four-body system is supposed to be decomposed into the inner triple (SMBH-star-star) and the outer triple (SMBH-stellar binary-SMBH). We survey the parameter space and determine the criteria analytically for the stellar mergers and the tidal disruption events (TDEs). For a relative distant and equal masses SMBH binary, the stars have more opportunities to merge as a result from the Lidov-Kozai (LK) oscillations in the inner triple. With a sample of tight stellar binaries, our numerical experiments reveal that a significant fraction of the binaries, ∼70 per cent, experience merger eventually. Whereas the majority of the stellar TDEs are likely to occur at a close periapses to the SMBH, induced by the outer Kozai effect. The tidal disruptions are found numerically as many as ∼10 per cent for a close SMBH binary that is enhanced significantly than the one without the external SMBH. These effects require the outer perturber to have an inclined orbit (≥40°) relatively to the inner orbital plane and may lead to a burst of the extremely astronomical events associated with the detection of the SMBH binary.

  9. High-speed binary CMOS image sensor using a high-responsivity MOSFET-type photodetector (United States)

    Choi, Byoung-Soo; Jo, Sung-Hyun; Bae, Myunghan; Choi, Pyung; Shin, Jang-Kyoo


    In this paper, a complementary metal oxide semiconductor (CMOS) binary image sensor based on a gate/body-tied (GBT) MOSFET-type photodetector is proposed. The proposed CMOS binary image sensor was simulated and measured using a standard CMOS 0.18-μm process. The GBT MOSFET-type photodetector is composed of a floating gate (n+- polysilicon) tied to the body (n-well) of the p-type MOSFET. The size of the active pixel sensor (APS) using GBT photodetector is smaller than that of APS using the photodiode. This means that the resolution of the image can be increased. The high-gain GBT photodetector has a higher photosensitivity compared to the p-n junction photodiode that is used in a conventional APS. Because GBT has a high sensitivity, fast operation of the binary processing is possible. A CMOS image sensor with the binary processing can be designed with simple circuits composed of a comparator and a Dflip- flop while a complex analog to digital converter (ADC) is not required. In addition, the binary image sensor has low power consumption and high speed operation with the ability to switch back and forth between a binary mode and an analog mode.

  10. Binary Oscillatory Crossflow Electrophoresis (United States)

    Molloy, Richard F.; Gallagher, Christopher T.; Leighton, David T., Jr.


    Electrophoresis has long been recognized as an effective analytic technique for the separation of proteins and other charged species, however attempts at scaling up to accommodate commercial volumes have met with limited success. In this report we describe a novel electrophoretic separation technique - Binary Oscillatory Crossflow Electrophoresis (BOCE). Numerical simulations indicate that the technique has the potential for preparative scale throughputs with high resolution, while simultaneously avoiding many problems common to conventional electrophoresis. The technique utilizes the interaction of an oscillatory electric field and a transverse oscillatory shear flow to create an active binary filter for the separation of charged protein species. An oscillatory electric field is applied across the narrow gap of a rectangular channel inducing a periodic motion of charged protein species. The amplitude of this motion depends on the dimensionless electrophoretic mobility, alpha = E(sub o)mu/(omega)d, where E(sub o) is the amplitude of the electric field oscillations, mu is the dimensional mobility, omega is the angular frequency of oscillation and d is the channel gap width. An oscillatory shear flow is induced along the length of the channel resulting in the separation of species with different mobilities. We present a model that predicts the oscillatory behavior of charged species and allows estimation of both the magnitude of the induced convective velocity and the effective diffusivity as a function of a in infinitely long channels. Numerical results indicate that in addition to the mobility dependence, the steady state behavior of solute species may be strongly affected by oscillating fluid into and out of the active electric field region at the ends of the cell. The effect is most pronounced using time dependent shear flows of the same frequency (cos((omega)t)) flow mode) as the electric field oscillations. Under such conditions, experiments indicate that

  11. Stability of binaries. Part II: Rubble-pile binaries (United States)

    Sharma, Ishan


    We consider the stability of the binary asteroids whose members are granular aggregates held together by self-gravity alone. A binary is said to be stable whenever both its members are orbitally and structurally stable to both orbital and structural perturbations. To this end, we extend the stability analysis of Sharma (Sharma [2015] Icarus, 258, 438-453), that is applicable to binaries with rigid members, to the case of binary systems with rubble members. We employ volume averaging (Sharma et al. [2009] Icarus, 200, 304-322), which was inspired by past work on elastic/fluid, rotating and gravitating ellipsoids. This technique has shown promise when applied to rubble-pile ellipsoids, but requires further work to settle some of its underlying assumptions. The stability test is finally applied to some suspected binary systems, viz., 216 Kleopatra, 624 Hektor and 90 Antiope. We also see that equilibrated binaries that are close to mobilizing their maximum friction can sustain only a narrow range of shapes and, generally, congruent shapes are preferred.

  12. Closing photoconductive semiconductor switches

    Energy Technology Data Exchange (ETDEWEB)

    Loubriel, G.M.; Zutavern, F.J.; Hjalmarson, H.P.; O' Malley, M.W.


    One of the most important limitations of Photoconductive Semiconductor Switches (PCSS) for pulsed power applications is the high laser powers required to activate the switches. In this paper, we discuss recent developments on two different aspects of GaAs PCSS that result in reductions in laser power by a factor of nearly 1000. The advantages of using GaAs over Si are many. First of all, the resistivity of GaAs can be orders of magnitude higher than that of the highest resistivity Si material, thus allowing GaAs switches to withstand dc voltages without thermal runaway. Secondly, GaAs has a higher carrier mobility than Si and, thus, is more efficient (per carrier). Finally, GaAs switches can have naturally fast (ns) opening times at room temperature and low fields, microsecond opening times at liquid nitrogen temperature of 77 K, or, on demand, closing and opening at high fields and room temperature by a mechanism called lock-on (see Ref. 1). By contrast, Si switches typically opening times of milliseconds. The amount of laser light required to trigger GaAs for lock-on, or at 77 K, is about three orders of magnitude lower than at room temperature. In this paper we describe the study of lock-on in GaAs and InP, as well as switching of GaAs at 77 K. We shall show that when GaAs is switched at 77 K, the carrier lifetime is about three orders of magnitude longer than it is at room temperature. We shall explain the change in lifetime in terms of the change in electron capture cross section of the deep levels in GaAs (these are defect or impurity levels in the band gap). In the second section, we describe the lock-on effect, now seen in GaAs and InP, and at fields as high as 70 kV/cm. We show how lock-on can be tailored by changing the GaAs temperature or by neutron bombardment. In the third section, we discuss possible lock-on mechanisms. 5 refs., 5 figs.

  13. Broadband fast semiconductor saturable absorber. (United States)

    Jacobovitz-Veselka, G R; Kellerm, U; Asom, T


    Kerr lens mode-locked (KLM) solid-state lasers are typically not self-starting. We address this problem by introducing a broadband semiconductor saturable absorber that could be used as a tunable, all-solid-state, passive starting mechanism. We extend the wavelength tunability of a semiconductor saturable absorber to more than 100 nm using a band-gap-engineered low-temperature molecular-beam-epitaxy (MBE)-grown bulk AlGaAs semiconductor saturable absorber in which the absorption edge of the saturable absorber has been artificially broadened by continuously reducing the Al concentration during the MBE growth. We demonstrate its tunability and its feasibility as a starting mechanism for KLM with a picosecond resonant passive mode-locked Ti:sapphire laser. The extension to femtosecond KLM lasers has been discussed previously.

  14. Organic Semiconductors and its Applications (United States)

    Kamalasanan, M. N.


    Organic semiconductors in the form of evaporated or spin coated thin films have many optoelectronic applications in the present electronic industry. They are frequently used in many type of displays, photo detectors, photoconductors for photocopiers and photovoltaic cells. But many p-conjugated molecules and polymer based devices do not provide satisfactory device performance and operational stability. Most of these problems are related to the interfaces they make with other organic materials and electrodes and the low conductivity of the organic layers. The study of organic-metal and organic—organic interfaces as well as electrical doping of organic semiconductors are very important areas of research at present. In this talk, I will be discussing some of the recent advances in this field as well as some of our own results in the area of interface modification and electrical doping of organic semiconductors.

  15. Catalysts, Protection Layers, and Semiconductors

    DEFF Research Database (Denmark)

    Chorkendorff, Ib


    Hydrogen is the simplest solar fuel to produce and in this presentation we shall give a short overview of the pros and cons of various tandem devices [1]. The large band gap semiconductor needs to be in front, but apart from that we can chose to have either the anode in front or back using either...... 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...

  16. Binary nucleation beyond capillarity approximation

    NARCIS (Netherlands)

    Kalikmanov, V.I.


    Large discrepancies between binary classical nucleation theory (BCNT) and experiments result from adsorption effects and inability of BCNT, based on the phenomenological capillarity approximation, to treat small clusters. We propose a model aimed at eliminating both of these deficiencies. Adsorption

  17. Discs in misaligned binary systems

    CERN Document Server

    Rawiraswattana, Krisada; Goodwin, Simon P


    We perform SPH simulations to study precession and changes in alignment between the circumprimary disc and the binary orbit in misaligned binary systems. We find that the precession process can be described by the rigid-disc approximation, where the disc is considered as a rigid body interacting with the binary companion only gravitationally. Precession also causes change in alignment between the rotational axis of the disc and the spin axis of the primary star. This type of alignment is of great important for explaining the origin of spin-orbit misaligned planetary systems. However, we find that the rigid-disc approximation fails to describe changes in alignment between the disc and the binary orbit. This is because the alignment process is a consequence of interactions that involve the fluidity of the disc, such as the tidal interaction and the encounter interaction. Furthermore, simulation results show that there are not only alignment processes, which bring the components towards alignment, but also anti-...

  18. Simulating relativistic binaries with Whisky (United States)

    Baiotti, L.

    We report about our first tests and results in simulating the last phase of the coalescence and the merger of binary relativistic stars. The simulations were performed using our code Whisky and mesh refinement through the Carpet driver.

  19. An adaptable binary entropy coder (United States)

    Kiely, A.; Klimesh, M.


    We present a novel entropy coding technique which is based on recursive interleaving of variable-to-variable length binary source codes. We discuss code design and performance estimation methods, as well as practical encoding and decoding algorithms.

  20. Magnetic braking in ultracompact binaries

    CERN Document Server

    Farmer, Alison


    Angular momentum loss in ultracompact binaries, such as the AM Canum Venaticorum stars, is usually assumed to be due entirely to gravitational radiation. Motivated by the outflows observed in ultracompact binaries, we investigate whether magnetically coupled winds could in fact lead to substantial additional angular momentum losses. We remark that the scaling relations often invoked for the relative importance of gravitational and magnetic braking do not apply, and instead use simple non-empirical expressions for the braking rates. In order to remove significant angular momentum, the wind must be tied to field lines anchored in one of the binary's component stars; uncertainties remain as to the driving mechanism for such a wind. In the case of white dwarf accretors, we find that magnetic braking can potentially remove angular momentum on comparable or even shorter timescales than gravitational waves over a large range in orbital period. We present such a solution for the 17-minute binary AM CVn itself which a...