GaSb and InAs: New Materials for Metal-Semiconductor Point-Contact Diodes

Metal-semiconductor point contact diodes have proved to be good detectors and mixers for radiation from the far-infrared to visible. Until now GaAs, InSb and InP are the most studied and used semiconductor materials for these devices. In this work we present the performance in the visible and infrared region for metal-semiconductor point-contact diodes with GaSb or InAs as the semiconductor layers. These two new materials have shown good characteristics.     

缓冲层对InSb/GaAs薄膜质量的影响

InSb是制作3~5μm红外探测器的重要材料。在GaAs衬底上外延生长InSb,存在的主要问题在于两种材料间14.6%的晶格失配度,会引入较大的表面粗糙度以及位错密度,使外延材料的结构和电学性能均会受到不同程度的影响。通过系列实验,研究了在生长过程中缓冲层对薄膜质量的影响。利用高能电子衍射仪(RHHEED)得到了合适的生长速率和Ⅴ/Ⅲ比,研究了异质外延InSb薄膜生长中低温InSb缓冲层对材料生长质量以及不同外延厚度对材料电学性质的影响。采用原子力显微镜(AFM)、透射电子显微镜(TEM)、X射线双晶衍射(DCXRD)等方法研究了InSb/GaAs薄膜的表面形貌、界面特性以及结晶质量。通过生长合适厚度的缓冲层,获得了室温下DCXRD半高峰宽为172″,77 K下迁移率为64300 cm²·V^-1·s^-1的InSb外延层。     

Sputtering of A 3 B 5 materials (GaP, GaAs, GaSb, InP, and InSb) by 2-to 14-keV N 2 + ions

Investigations of the general characteristics and distinctive features of sputtering of A ³ B ⁵ materials (GaP, GaAs, GaSb, InP and InSb) under bombardment with N ₂ ⁺ ions have been carried out. From the experimental data, dependences of the sputtering yield of these materials on the incidence angle and ion energy have been obtained and the surface relief patterns produced by target etching have been studied. It has been shown that the dependence on energy of the sputtering yield for GaP, GaAs, and InP can be adequately described by the Haffa-Switkovski formula for binary materials and Yudin’s approximation for elemental targets. Sputtering of GaSb and InSb proceeds in the surface layer recrystallization mode, and the sputtering yield agrees with calculations based on Onderlinden’s model. From a comparison of the experimental and calculated dependences, the surface bonding energies have been determined.     

Noise reduction in sputtered W/GaAs Schottky junctions

The noise characteristics of sputtered W/GaAs Schottky diodes, annealed at temperatures up to 700°C, have been investigated. A useful figure of merit for such millimeter and submillimeter mixer diodes is the noise performance at an RF where accurate measurements are available. Noise temperatures measured at a typical mixer intermediate frequency of 4GHz under DC biased conditions have been reduced significantly by rapid thermal annealing. The best noise data have been obtained with an annealing time of 2 minutes at 600°C and are consistent with good mixer performance.     

Surface morphology of highly mismatched InSb films grown on GaAs substrates by molecular beam epitaxy

InSb films on GaAs(001) substrates with and without GaAs buffer layer have been grown by molecular beam epitaxy. Rather than surface undulations, aligned ripples and pyramidal hillocks along the orthogonal 〈110〉 directions were observed on the surface of InSb films. Both the preferential growth and the termination of ripples were proved to be related to strain‐driven mass transport. A model was proposed to elucidate the formation of the hillocks, which are more efficient to relax strain than ripples. Due to the strain relaxation through hillocks with small bases predominantly, the surfaces of the InSb films grown without a GaAs buffer layer are smoother than those of films grown with a GaAs buffer layer. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Low noise oscillator approaches at 140 GHz

Conclusion It was demonstrated that approaches towards oscillators with sufficient noise performance familiar up to frequencies of 100 GHz can be applied at 140 GHz with only minor modifications.Mostly due to the limitations imposed by the available InP Gunn diodes the power levels reached with second harmonic mode operation were less than at 94 GHz with GaAs devices. The two approaches employing IMPATT diodes deliver substantial output power at D-band. Which one is preferrable will be dependent on the application.     

Enhanced optical nonlinearities of superlattices within the Kronig-Penney model incorporating inherent bulk nonlinearities

Third order nonlinear optical susceptibilities χ⁽³⁾ of GaAs/Ga_1?xAlAs superlattices have been predicted which are two orders of magnitude larger than those of bulk GaAs. This enhancement is due to the band nonparabolicity arising from the additional periodicity of the superlattice. These predictions, based on a tight-binding model of the superlattice dispersion, are here extended to the more realistic Kronig-Penney (KP) model. Corrections to tight-binding are non-negligible; however, enhancements of χ⁽³⁾ are still large but reduced approximately 30%–50% over previous estimates. The KP model is also here applied to superlattices employing InSb as the quantum well material. Because of the smaller effective mass of InSb, and taking account of its bulk nonparabolicity, the minibands move to higher energy, enhancing the interwell overlap and increasing χ⁽³⁾ by about one order of magnitude over that of bulk InSb. The role of the barrier material in this case is important and is discussed. The interplay between the bulk nonparabolicity and that arising from the superlattice is also addressed.     

Influence of ultrasonic vibrations on the growth of semiconductor single crystals

The influence of ultrasonic vibrations on striations in InSb, GaAs and Bi-Sb alloy single crystals grown by a modified Czochralski method was investigated. Ultrasonic vibrations at frequencies of 0.15, 0.25, 0.6, 1.2, 2.5, 5 or 10 MHz were introduced into the melt parallel to the pulling axis. The introduction of ultrasonic vibrations at a frequency up to 5 MHz eliminates the striations in GaAs and Bi-Sb alloy single crystals growing with constant diameter. It was found that for Bi-Sb alloy single crystals of constant diameter growth, after ‘processing’ of the melt with ultrasonic vibrations, the striations do not reappear until after 2 h. The effectiveness of the influence of the ultrasonic vibrations on the decrease of growth striations in InSb, GaAs and Bi-Sb alloy growing crystals was estimated with the help of the calculation of the sound absorption coefficient.     

Intervalley Γ- X Deformation Potentials in Ⅲ-V Zincblende and Si Semiconductors by Ab Initio Pseudopotential Calculations

Intervalley Γ- X deformation potential constants (IVDP's) have been calculated by first principle pseudopotential method for the Ⅲ-V zincblende semiconductors Alp, AlAs, AlSb, Gap, GaAs, GaSb, InP, ZnAs and ZnSb. As a pro to type crystal we have also carried out calculations on Si. When comparing the calculated IVDP's of LA phonon for Gap, InP and InAs and LO phonon for AlAs, AlSb, GaAs, GaSb and InSb with a previous calculation by EPM in rigid approximation, good agreements are found. However, our ab initio pseudopotential results of LA phonon for AlAs, AlSb, GaAs, GaSb and InSb and LO phonon for Gap, InP and ZnAs are about one order of magnitude smaller than those obtained by EPM calculations, which indicate that the electron redistributions upon the phonon deformations may be important in affecting Γ- X intervalley shatteri'ngs for these phonon modes when the anions are being displaced. In our calculations the phonon modes of LA and LO at X point have been evaluated in frozen phonon approximation. We have obtained, at the same time, the LAX and LOX phonon frequencies for these materials from total energy calculations. The calculated phonon frequencies agree very well with experimental values for these semiconductors.     

Measurement of low-frequency noise in tunnel diodes

Conclusions Our studies have revealed that the spectral density of low-frequency current fluctuations in GaAs tunnel diodes can be described by the relation Wi(u, F)=f² (u)mF^–, where the nonlinear function f²(u) is not proportional to the rms of excess diode current. The flicker nature of the current noise in tunnel diodes derives from conductance fluctuations on the p-n junction, which occur in tunnel diodes as well as in low-noise transistors at frequencies ranging from near zero to a few kiloheriz and produce noise of almost the same absolute intensty in both kinds of devices.Leningrad Polytechnic Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 20, No. 5, pp. 777–784, May, 1977.     

Far-infrared spectroscopy of impurities in semiconductors

Far-infrared spectroscopy of the electronic transitions between bound states of impurities provides a very high resolution technique for studying chemical shifts and thereby identifying residual contaminants. The use of photoconductivity generated within the sample itself, usually by the photothermal mechanism (“photothermal ionisation spectroscopy”), enables very high sensitivity to be achieved even with very thin films or ultrahigh-purity material. The current knowledge about the identity of the residual shallow donors in GaAs, InP, InAs and InSb obtained with this technique is reviewed. With high-purity materials the magneto-optical spectrum of the shallow donors can be particularly rich and more than fifty lines can be observed with both GaAs and InP.

Hydrostatic pressure provides a valuable additional experimental parameter in studies of impurities. Not only does the pressure-induced increase in mass improve the resolution of the “fine structure” due to different chemical species but additional states can be introduced into the forbidden energy gap. Results with both InSb and GaAs have shown that generally donors in direct-gap III-V materials may be expected to have three types of state: the familiar gamma-associated donors, localised states with A₁ symmetry which are normally resonant within the conduction band and metastable DX states.

Negatively charged shallow donor states (D^- states) and “molecular” combinations where the electrons are shared between two or more donor sites have been studied by infrared spectroscopy of III-V materials. These states are important precursors of the metal-insulator transition.

Recently there have been a number of studies of impurities within quantum wells and heterostructures. The dependence of impurity energy on distance from the well edge has been established and it has been shown that high concentrations of D^- states can be formed by remote deping of the structures.     

Potential electrical characteristics of interference transistors made from various materials

A theoretical analysis of the electrical characteristics of GaAs, InAs, InSb, and Si quantum interference T transistors is performed with consideration of the dependence of the effective masses on the quantum wire dimensions. It is shown for extremely small wire dimensions that none of the materials has significant advantages over the others with respect to the frequency characteristics of the transistors investigated. Zh. Tekh. Fiz. 69, 130–131 (November 1999)     

Electrical characterization of argon-ion sputtered n-GaAs

Epitaxially grown n-type GaAs was sputtered with 0.5 keV Ar ions at doses of 10¹² and 10¹⁵ ions/cm². The sputter-induced defects in the GaAs were characterized using deep-level transient spectroscopy (DLTS) and the effect of these defects on the characteristics of Au Schottky barrier diodes (SBD's) fabricated on the sputtered GaAs was evaluated by current-voltage measurements. It was found that the barrier height of the SBD's decreased with ion dose from 0.97 eV for unsputtered diodes to 0.48 eV after sputtering at a dose of 10¹⁵/cm². DLTS showed the presence of a multitude of sputter-induced defects at and near the GaAs surface. The defects formed during the initial stages of sputtering had the same properties as some of the primary defects introduced during electron and proton irradiation of GaAs. Isochronal annealing at temperatures of up to 350°C showed that although some defects were removed by annealing, others appeared.     

Detection and Mixing Properties of an InSb Metal-Semiconductor Point Contact Diode

We present preliminary data on the performance of a new fast photodetector based on a W–InSb metal-insulator-semiconductor point contact diode operating at room temperature and with no bias voltage. The device can work either as a video detector or as harmonic mixer for radiation from far–infrared (FIR) to visible. In the FIR region, for wavelengths from 200 to 400 m, the W–InSb point contact diode showed a sensitivity comparable to that of Golay cells. In the visible region the device showed a video and heterodyne detection responsivity much higher with respect to standard M.I.M. point contact diodes. Owing to its ruggedness, low cost and wide band of operation, the W–InSb point contact diode may be very attractive as a general purpose optical sensor.     

Laser-induced damage in InSb at 1.06 μm wavelength—a comparative study with Ge, Si and GaAs

This paper deals with the study of laser-induced damage in n-type single crystal InSb irradiated with a Nd: glass laser of 1.06 μm wavelength and 300 μs pulse duration. Samples of different surface quality were prepared by mechanical lapping and polishing by diamond paste. Evolution of damage morphological features observed at different power densities is discussed. Damage threshold results are analysed in terms of a thermal model taking into account the temperature dependence of various physical parameters and using the finite difference method of calculation. A comparative study of laser induced damage in InSb, Ge, Si and GaAs irradiated under similar conditions is also presented.     

Charge transfer from chemical shifts at (110) surfaces of III–V compound semiconductors

Surface charge-transfer are calculated from surface core-level shifts determined by Eastman et al. and Taniguchi et al. by using soft X-ray photoemission spectroscopy. A simple electrostatic model which was first applied by Shevchik et al. to the analysis of bulk data is adapted for surfaces of compound semiconductors. The charge transferred from cations to anions is found to be the same in the bulk and at the (110) surfaces of GaP, GaAs, GaSb, and InSb.     

First-principles study of interface relaxation effect on interface and electronic structures of InAs/GaSb superlattices with different interface types

We have implemented first-principles relativistic pseudopotential calculations within general gradient approximation to investigate the structural and electronic properties of quaternary InAs/GaSb superlattices with an InSb or GaAs type of interface. Because of the complexity and low symmetry of the quaternary interfaces, the interface energy and strain in the InAs/GaSb superlattice system have been calculated to determine the equilibrium interface structural parameters. The band structures of InAs/GaSb superlattices with InSb and GaAs interfaces have been calculated with respect to the lattice constant and atomic position relaxations of the superlattice interfaces. The calculation of the relativistic Hartree–Fock pseudopotential in local density approximation has also been performed to verify the calculated band structure results that have been predicted in other empirical theories. The calculated band structures of InAs/GaSb superlattices with different types of interface (InSb or GaAs) have been systematically compared. We find that the virtual–crystal approximation fails to properly describe the quaternary InAs/GaSb superlattice system, and the chemical bonding and ionicity of anion atoms are essential in determining the interface and electronic structures of InAs/GaSb superlattice system.     

Manifestation of 1/<Emphasis Type="Italic">f</Emphasis> leakage noise in nanoscale light-emitting structures

We present the results of studies of the 1/f noise spectrum in light-emitting diodes and lasers with nanoscale structures based on GaAs and its solid solutions. Leakage current was detected from an analysis of I–V characteristics and voltage noise spectrum dependences on the current. Leakage current appeared to be the main source of noise in the samples and leads to intensity fluctuations of the spontaneous radiation. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 2, pp. 149–161, February 2008.     

Non equilibrium phonon distribution and electron-phonon coupling in semiconductors

A comparison is made for different semiconductors, of the non equilibrium phonon distributions induced by photon absorption. It is found that energetic carriers create preferentially LO-phonons for GaAs where Fröhlich type interaction dominates. For Si and the intermediate case of InSb the energetic carriers still relax through optical phonons. For InSb LO- and TO-phonons participate in the same proportion. Highest phonon temperatures are obtained in the layer semiconductor GaSe.     

Microscopical studies at cadmium impurities in compound semiconductors

Molecule-like defect complexes have been studied at Cd acceptors in the III–V semiconductors GaAs, GaP, InP, InAs, and InSb by PAC spectroscopy. After hydrogen plasma treatment, the formation of Cd-H complexes was observed in all these compounds. Additionally, the formation and stability of Cd-S and Cd-Se pairs in GaAs have been analyzed.