Growth Kinetic Studies for MOCVD CdTe and HgCdTe Epilayers on GaAs Substrates

The growth rates of CdTe and CMT on GaAs and on CdTe / GaAs substrates were studied as a functionof temperature and gas composition. A Langmuir-Hinshelwood Model for surface reaction control region issuggested. The CdTe/GaAs interface was examined by X-ray double crystal diffraction, laser Ramanspectroscopy and transmission electron microscopy (TEM). A defect layer was observed at CdTe / GaAs inter-face. The relationship between interface qualities and electrical properties of CMT overlayers was discussed.     

Characterization of GaSb Films by Metalorganic Chemical Vapour Deposition

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Preparation and Interface Studies on HgCdTe/CdTe/GaAs Grown by MOCVD

When we use MOCVD technique,an excellent CdTe epi-layer was grown on GaAs substrates and theCdTe/GaAs hybrid substrates suitable for growing Hg_(1-x)Cd_xTe(CMT)were obtained.The x value in CMT isbetween 0.2 and 0.8.The electrical properties of CMT depend upon the thickness of CdTe epi-layers.TheCdTe/GaAs interface was examined by both scanning electron microscope(SEM)and electron auger spectra(EAS).The influence of defects observed at interface on electrical and optical properties of CMT fihns was dis-cussed.     

MOCVD Growth of GaAs / Al_xGa_(1-x) As Superlattices

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Low temperature OMVPE growth of ZnSe withTertiary-butyl allyl selenide and dimethylzinc-triethylamine

The growth of high quality ZnSe by organometallic vapor phase epitaxy (OMVPE) has been investigated fortertiary-butyl allyl selenide (tBASe), combined with dimethylzinc-triethylamine (DMZn : NEt₃). Single crystalline ZnSe films were grown on GaAs at temperature as low as 350°C with a reasonable growth rate (~1 µm/h). Secondary ion mass spectrometry (SIMS) spectra show a negligible carbon incorporation in ZnSe films from tBASe even at high VI/II ratio, in contrast the carbon concentration of 10²¹ cm^-3 in ZnSe films grown from diallyl selenide (DASe)and methylallylselenide (MASe). Good surface morphology, crystalline and interface quality of ZnSe on (001) GaAs are confirmed by scanning electron microscopy, double crystal diffractometry (DCD) and Rutherford backscattering spectrometry (RBS). Photoluminescence at 10K shows sharp near-band-edge excitonic spectra.     

MOCVD Growth of Doped GaAs/AlGaAs Quantum Heterostructures

The influences of growth techniques of AP-MOCVD GaAs/AlGaAs silicon-doped multi-quantum wells(MQWs), heterostructure bipolar transistors (HBTs), double barrier resonant tunneling diodes(DBRTDs) ontheir structures and performances were studied. Continuously grown MQWs, that is, no growth interruption atthe heterointerfaces, shown blue-shifted, narrower and stronger photoluminescence(PL) compared withinterruptedly grown ones.TEM examination of the interrupted interfaces revealed a bright line correspondingto the compositional fluctuation and impurity adsorption, and indicated noncommutative structures ofAlGaAs/GaAs and GaAs/AlGaAs interfaces. High performance HBTs and DBRTDs were obtained bycontinuously grown method while growth interruption caused performance degradation. It was concluded thatgrowth interruption may cause accumulation of residua1 impurities in the ambient as well as compositionalfluctuation while continuous growth at very low growth rates can overcome such problems.     

A Phase Investigation of the Rh-Ga-As System

The Rh- Ga- As solid- state equilibrium phase diagram was determined at 800 °C with the use of powder X- ray diffraction (XRD), electron probe microanalysis (EPMA), and scanning electron microscopy (SEM). No ternary Rh- Ga- As phases were found, and very limited solid solubility was measured in GaAs and the constituent binary Rh- Ga and Rh- As compounds. GaAs, RhGa, and RhAs2 form a three- phase region that dominates the GaAs side of the phase diagram. The existence of this three- phase region confirms previous observations that RhGa and RhAs2 are the stable phases when Rh thin films are completely reacted on GaAs.     

Investigation of EL2 Defect in 10 MeV Electron Irradiated Undoped Semi－insulating LEC GaAs

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Phase equilibria in the Nb-Ga-As system below 1000 °C

The Nb-Ga-As solid state equilibrium phase diagram was determined at 600 °C with the use of powder X-ray diffraction (XRD), electron probe microanalysis (EPMA), and scanning electron microscopy (SEM). No ternary Nb-Ga-As phases were found, and limited solid solubilities were measured in the constituent binary Nb-Ga and Nb-As compounds. The phases GaAs, NbGa₃, and NbAs coexist with each other to form a three-phase equilibrium that dominates the GaAs side of the phase diagram. The phase diagram is in agreement with interfacial reaction studies, which have shown that NbGas and NbAs are the stable phases when Nb thin films are reacted to completion on GaAs.     

Modified AlAs/GaAs Double Barrier Quantum Resonant Tunneling Diodes Grown by AP-MOCVD

The MOCVD growth of modified AlAs/GaAs double barrier resonant tunneling diodes(DBRTD)withan A1GaAs chair was reported.The resonances to the first excited states were obtained.The peak-to-valley cur-rent ratio(PVCR)is 1.3 at 77K,room temperature peak current density is 8 kA/cm~2.The resonance voltagesare in agreement with the theoretical approach by transfer-matrix method.Influence of interrupted growthtime at the hetero-interface and incorporation of the AlGaAs chair to the device performances were studiedand the mechanism was discussed.The attempt to add an AlGaAs chair to the DBRTD by MOCVD resultedin improvement in the PVCR and peak current density.     

Kinetic study on uniformity of AlGaAs grown by MOVPE

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InGaP/InGaAs/GaAs DHBT structural materials grown by GSMBE

Heterojunction bipolar transistor (HBT) is of great interest for the application to microwave power and analog circuits.As known, decreasing bandgap energy of the base layer in HBT can result in a smaller turn-on voltage.Using InGaAs as a base material in GaAs HBT is a possible approach to achieve the aim.In this work, a novel InGaP/InGaAs/GaAs double heterojunction bipolar transistor (DHBT) structure with an InGaAs base was designed and grown by gas source molecular beam epitaxy (GSMBE).High-quality InGaAs/GaAs hetero epi-layers and a good doping figure were obtained through optimizing the layer structure and the growth condition.The DHBT devices of a 120 μm×120 μm emitter area were fabricated by normal process and the good DC performance was obtained.A breakdown voltage of 10 V and an offset voltage of just 0.4 V were achieved.These results indicate that the InGaP/InGaAs/GaAs DHBT is suitable for low power-dissipation and high power applications.     

Ga-rich precipitates in Fe ion implanted GaAs

Gallium-rich precipitates (named as γ′-Ga(Fe)) were observed in Fe ion implanted and annealed GaAs. Transmission electron microscopy (TEM) analysis shows that these precipitates have an orthorhombic structure (γ-Ga-type) with lattice parameters of a=1.04 nm, b=1.298 nm and c=0.511 nm. Most of these precipitates grow in GaAs as threefold-twinned hexagonal cylindrical particles with their hexagonal cylindrical axes running along the [110]_γ′-Ga(Fe) direction. The γ′-Ga(Fe) phase is stable either under the electron beam irradiation or at room temperature.     

Characterizing III–V heteroepitaxial structures

A complementary characterization scheme for high-volume production of III–V heteroepitaxial structures is described, focusing on the cost-effectiveness and utility of the techniques, AlGaAs/InGaAs/GaAs heteroepitaxial layers grown by molecular beam epitaxy were studied by cross-sectional transmission electron microscopy (TEM) and photoluminescence (PL) techniques. The presence of a range of layer thicknesses, fine periodic striation contrast due to Al composition variations, and layer contrasts in the lattice images observed by TEM in selected samples are discussed. The utility of room-temperature PL characterization for AlGaAs/InGaAs/GaAs heteroepitaxial layers is presented. Measures of layer thicknesses and alloy content as well as overall psuedomorphic high-electron-mobility transistor quality and channel sheet charge are derived from the PL signatures.     

An investigation of the Ir-Ga-As system

The Ir-Ga-As solid-state equilibrium phase diagram was determined at 600 °C with the use of X-ray powder diffraction, electron probe microanalysis, and scanning electron microscopy. No ternary Ir-Ga-As phases were found and very limited solid solubility was measured in GaAs and the constituent binary Ir-Ga and Ir-As compounds. GaAs, Ir₃Ga₅, and IrAs₂ were found to form a three-phase region which dominates the GaAs side of the phase diagram. The existence of this three-phase region confirms previous observations that Ir₃Ga₃ and IrAs₂ are the stable phases when Ir thin-films are completely reacted on GaAs.     

Effect of growth interruption and strain buffer layer on PL performance of AlGaAs／GaAs／InGaAs quantum well for 1065 nm wavelength lasers

Strained InGaAs/GaAs quantum well (QW) was grown by low-pressure metallorganic chemical vapor deposition (MOCVD). Growth interruption and strain buffer layer were introduced to improve the photoluminescence (PL) performance of the InGaAs/GaAs quantum well. Good PL results were obtained under condition of growth an interruption of 10 s combined with a moderate strain buffer layer. Wavelength lasers of 1064 nm using the QW were grown and processed into devices. Broad area lasers (100 μm × 500 μm) show very low threshold current densities (43 A/cm2) and high slop efficiency (0.34 W/A, per facet).     

Structural features of tilt grain boundaries in GaAs thin films

(fa181-1) and low-angle tilt grain boundaries in GaAs thin films were investigated by high-resolution transmission electron microscopy (HRTEM). Models for the atomic structure of the boundaries are proposed in this study. The structural unit for the boundaries consists of 5- and 7-member rings. The polarity of the grain on either side of the boundaries was confirmed by the convergent beam electron diffraction method. (110) low-angle tilt grain boundaries were observed to consist of a/2<110> edge dislocations. Anti-site type bonds are present at the core of the dislocations.     

Atomic-layer epitaxy for heterostructures

Atomic-layer epitaxy offers the ultimate control of interface abruptness and thickness uniformity across a large-area wafer. In the work reported here, GaAs, AlGaAs, and InGaP were grown by atomic-layer epitaxy with one monolayer of growth per deposition cycle. Atomic-layer-epitaxy-grown AlGaAs/ GaAs quantum well structures showed excellent thickness uniformity, and resonant tunneling diodes showed excellent uniformity in both threshold voltage and threshold current. GaInP/GaAs quantum structures were grown and studied; they had well widths as thin as One lattice constant. This 5.6 Å GaAs quantum well is believed to be one of the thinnest grown in this material system.     

Ⅲ-Ⅴ族三元化合物半导体材料分子束外延的生长热力学

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△G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。     

压痕诱导单晶GaAs非晶相变

利用高分辨电子显微镜观察了(100)GaAs单晶Vickers压痕诱发的形变行为.结果表明,这种材料在Vickers硬度计载荷的作用下产生许多孪晶和堆垛层错,导致发生晶格扭曲,最终诱发晶体的非晶转变.孪晶、层错和晶格扭曲很可能是压痕诱发GaAs非晶转变过程中经历的变形阶段.