Characterization of GaAs layers grown on polycrystalline GaAs by LPE and current controlled LPE

It is the purpose of this paper to investigate the suitability and effectiveness of growth of thin GaAs layers on polycrystalline GaAs substrates by liquid phase epitaxy (LPE) and current controlled LPE (CCLPE). During each growth run LPE and CCLPE were used to grow thin GaAs layers on two large-grain polycrystalline GaAs substrates cut from the same wafer and simultaneously placed in the same growth system. The grain boundary was exposed by cleaving the samples perpendicular to the grain boundary. Notnarski contrast, SEM, C-V and Hall measurements were performed in order to determine the surface morphology, discontinuity of epilayer at the grain boundary, epilayer thickness unform-ity, resistivity (in directions parallel and perpendicular to the grain boundary), and dopant concentration. The CCLPE system was carefully designed so that growth would take place only by electrotransport in the absence of convection or Peltier cooling. The results indicate that CCLPE yields layers with improved surface morphology and thickness uniformity as compared to those grown by LPE. In some samples the epilayer was discontinuous at certain grain boundaries. Results are presented on CCLPE growth rate dependence upon grain orientation, current density, and continuity of the epilayer at the grain boundary.     

Substrate quality impact on the carrier concentration of undoped annealed HgCdTe LPE layers

The impact of Te precipitates and impurities, in CdZnTe or CdTe substrates, on grown liquid phase epitaxy (LPE) HgCdTe layer hole concentrations was studied. The carrier concentrations in capped annealed LPE HgCdTe layers grown on CdZnTe substrates with large densities of Te precipitates are frequently significantly higher than those expected for HgCdTe annealed under Hg-deficient conditions. The carrier concentration in the LPE layer, due to the diffusion of copper ions from contaminated CdTe substrates into the layer, is strongly affected by the polarity of the (111)-oriented substrates. Layers grown on the (111)A face showed very high concentrations of Cu, whereas in those grown on the (111)B face normal carrier concentrations were achieved. These phenomena are discussed on the basis of defects formed either in the epilayer or in the layer-substrate interface.     

Study of grown-in defects and effect of thermal annealing in Al0.3Ga0.7As and GaAs LPE layers

Studies of the grown-in deep-level defects in the undoped n-Al_xGa_1-xAs (x = 0.3) and GaAs epitaxial layers prepared by the liquid phase epitaxy (LPE) techniques have been made, using DLTS, I-V and C-V measurements. The effect of 300 °C thermal annealing on the grown-in defects was investigated as a function of annealing time. The results showed that significant reduction in these grown-in defects can be achieved via low temperature thermal annealing process. The main electron and hole traps observed in the Al_0.3Ga_0.7As LPE layer were due to the E_c-0.31 eV and E_v+0.18 eV level, respectively, while for the GaAs LPE layer, the electron traps were due to the E_c-0.42 and 0.60 eV levels, and the hole traps were due to E_v+0.40 and 0.71 eV levels. Research supported in part by the Air Force Wright Aeronautical Laboratories, Aeropropulsion Lab., Wright Patterson Air Force Base, Ohio, subcontract through SCEEE, contract F33615-81-C-2011, task-4, and in part by AFOSR grant no. 81-0187.     

The growth of buffered GaAs mesfet structures by LPE

Layers of LPE GaAs have been grown with background carrier levels in the low 10¹⁴ cm⁻³ range by systematic bakeouts of the Ga melts together with between-run loading in a dry N₂ environment. High resistivity layers in the range 10₃-10⁴Ω cm have been grown by making use of the compensation of free carriers by the out diffusion of Cr from the substrate. Intentional Cr-doping from the melt resulted in layers with poor surface morphologies. Buffered MESFET structures have been grown which show near ideal carrier concentration profiles and which do not exhibit interfacial space charge effects.     

InGaAsP/GaAs单量子阱SCH半导体激光器的液相外延

利用一种改进的液相外延技术进行了ＧａＡｓ衬底上ＩｎＧａＡｓＰ材料的生长，１０Ｋ温度下光荧光半宽度（ＦＷＨＭ）为１４ｍｅＶ，获得了阈值电流密度为３００Ａ／ｃｍ２的ＳＣＨ多层结构外延片，宽台面激光器最大连续输出功率达到２．１Ｗ。     

LPE—GaAs掺Er的研究＊

本文采用液相外延(LPE)法研究在GaAs中掺鼯土元素Er的外延生长,并对外延层的质量及光荧光等测量结果进行讨论。     

Ge在GaAs液相外延中的行为

本文用霍耳、SIMS、电化学C-V和光致发光等方法,研究了在550℃至950℃生长温度范围内 LPE GaAs中Ge的分凝行为以及占Ga位Ge原子与占As位Ge原子的占位比.得到Ge的分凝系数随生长温度降低而增大,占位比Ge_(Ga)/Ge_(As)随生长温度降低而减小.     

Spectral characteristics of GaAs solar cells grown by LPE

This paper describes the spectral characteristics of GaAs solar cells grown by low-temperature liquid phase epitaxy (LPE). It demonstrates improvements in blue response and peak internal quantum efficiencies of 100 percent for an optimized cell structure with isovalent In doped base and ultrathin (<100Å) heavily doped cap p⁺-GaAs layer on the photosensitive surface. The conversion efficiency obtained from the optimized cells under one-sun AM 1.5 conditions is 23.4 percent. Our results indicate that the low-cost LPE-grown films are suitable for high-efficiency solar cells.     

The study of lattice match in GaInAsP/InP heterojunction LPE layers

The effects of the growth conditions of two-phase solution liquid phase epitaxy (LPE) (i.e. growth temperature, cooling rates and solution composition) on lattice mismatch and band-gap wavelength in GaInAsP/InP heterojunction LPE layers have been investigated by X-ray doublecrystal diffractometry and double-beam spectrophotometry. The stress in the grown interface free of misfit dislocations and lattice mismatch at growth temperature have been calculated.     

Doping of LPE layers of CdTe grown from te solutions

Good quality epitaxial layers of CdTe have been grown by LPE from Te-rich solutions at ˜ 500‡C onto (111) CdTe substrates. The layers have been characterised by a wide variety of techniques including capacitance-voltage profiling, photoluminescence at 4K and secondary-ion mass spectrometry (SIMS) . Undoped layers had good electrical properties (p ˜ 1 × 10¹⁶ cm⁻³, L_e ˜ 3 μm) and SIMS showed the layers to be of high purity. Those doped with In and Al however, had low n-type carrier concentrations and very short diffusion lengths, while the photoluminescence spectra showed a strong peak at ˜ 1.4 eV commonly seen in n-type bulk CdTe. The most heavily doped layers showed marked decreases in lattice parameter.     

MBE生长中缓冲层对InSb/GaAs质量影响的研究

用分子束外延(MBE)方法在GaAs(001)衬底上外延生长了InSb薄膜,并研究了异质外延InSb薄膜生长中缓冲层对材料质量的影响.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272",迁移率为64 300 cm2V-1s-1的InSb外延层.     

Investigation of high quality GaAs:In layers grown by liquid phase epitaxy

Indium-doped GaAs layers are investigated by low-field Hall effect, photoluminescence, and double crystal x-ray diffraction in order to study the influence of the In concentration on the electrical, optical, and crystallographic properties. The layers were grown by liquid phase epitaxy from solution with In concentrations in the range 0–10 at.%. It was found that epitaxial growth from the melt with 7 at.% In content produces the highest quality epitaxial layers.     

Annealing effect in Si-doped GaAs and AlGaAs layers grown by MBE

The effect of annealing on Si-doped GaAs and Al0·3Ga0·7As layers grown by MBE has been studied. In the heavily doped samples, the donor concentration decreased considerably and the broad luminescence characteristic of the SA centre reported in bulk n-GaAs appeared. The results suggest evidence that annealing converts some of the Si donors into complexes like the SA centre, which does not act as a donor.     

用回熔再生长LPE工艺制备高效AlGaAs／GaAs太阳电池

报道了采用欠饱和溶液的回熔—再生长液相外延（ＬＰＥ）方法制备高效ＡＩｘＧａ１－ｘＡｓ／ＧａＡｓ异质结构太阳电池的工艺。研究表明，与传统的过冷生长技术相比，回熔工艺对衬底质量的要求不严格，且能形成有利于光生少子被收集的带隙结构。在工艺优化的情况下，获得大阳电池的全面积转换效率在ＡＭ０，１ｓｕｎ的测试条件下为１８．７８％（０．７２ｃｍ２），在ＡＭ１．５，１ｓｕｎ下为２３．１７％。     

Structural and electrical contact properties of LPE grown GaAs doped with indium

We have studied the effects of In doping on the structural and electrical properties of a liquid phase epitaxially (LPE) grown GaAs. The results of surface morphology studies show that macroscopically, a terrace-free area in certain regions can be seen on the surface of a GaAs layer doped with In of 2.4 × 10¹⁹ cm³. The full widths at half-maximum (FWHM) of x-ray double crystal rocking curves show that a GaAs epi-layer of good crystalline quality can be obtained by doping In to a concentration up to 4.3 × 10¹⁹ cm^-3, beyond which a sharp increase in the FWHM is observed. Etch pit density (EPD) study also shows that the dislocation density is reduced by doping the epi-layer with In. At an optimum In concentration, 2.4 × 10¹⁹ cm^-3, the EPD was reduced by a factor of 20 when measured at the surface of a 9μm thick epi-layer. The I-V characteristics of Au-GaAs Schottky diodes show, for the layer with an optimal In concentration, an ideality factor close to 1.04 over more than seven decades of current. For the same layer, the reverse I-V characteristics are close to an ideal Schottky diode and could be fitted by a theoretical curve, combining the thermionic field emission and thermionic emission. For doping levels higher than 6 × 10¹⁹ cm^-3, the epitaxial layer quality deteriorated. We report the results obtained from the Nomarski optical microscope, double crystal x-ray rocking curves, etch pit density, forward and reverse I-V characteristics, and the theoretical current transport models.     

Electrical properties of indium-doped LPE layers of Pb1−xSnx Te

Liquid-phase epitaxial (LPE) layers of Pb_1−xSn_xTe with an alloy composition 0≤×≤0.25 were doped n-type by adding from 0.002 to 10 at.% indium to the growth solution. Doping characteristics of indium and electrical properties of the epilayers at 77 and 4.2K were studied by Hall and resistivity measurements made directly on the grown layers. Electron concentration and mobility at 77 and 4.2K are presented as a function of indium doping for various x values. Doping coefficients of ~0.05 and ~0.03 are found for PbTe and Pb_0.8Sn_0.2Te, respectively, grown at ~450°C. For medium to high indium doping, the electron concentration saturates to a constant value independent of doping and LPE growth temperature. The saturation values decrease substantially with increasing x and increase with a decrease in sample temperature. Bulklike mobilities practically independent of doping are recorded up to an indium concentration N_ln~0.3 at.%, above which the mobility decreases with increasing indium concentration. The data shows that indium is a suitable donor in liquid-phase epitaxial layers of Pb_l-XSn_xTe.     

Photoluminescence of Si-doped GaAs epitaxial layers

The effect of arsenic pressure on the amphoteric behavior of Si during the growth of the Si-doped (100)-, (111)Ga-, and (111)As-oriented GaAs layers is studied by photoluminescence spectroscopy. The edge luminescence band is examined, and the concentration and the degree of compensation as functions of the arsenic pressure are determined. Nonstoichiometry defects in GaAs layers grown with a deficit and an excess of arsenic are studied. It is shown that the defects formed in the (111)Ga- and (111)As-oriented layers are different in nature.     

Low-threshold InGaAsP/InGaP lasers at 810 nm grown on GaAs substrate by LPE

InGaAsP/InGaP double-heterostructure lasers emitting at 810 nm have been fabricated on GaAs substrates using liquid-phase epitaxy (LPE). A threshold current as low as 2.0 kA/cm2 with an external differential quantum efficiency of 54% is obtained. Thus it has been shown that high-quality InGaAsP/InGaP lasers can be obtained by LPE growth.