Influence of buffer layer thickness and epilayer’s growth temperature on crystalline quality of InAs0.6P0.4/InP grown by LP-MOCVD

InAs_0.6P_0.4 epilayers grown on InP (100) substrates using two-step growth method by LP-MOCVD were investigated. A low temperature (450 °C) In_0.18Ga_0.82As buffer layer was introduced to relax the lattice mismatch between the InAs_0.6P_0.4 epilayer and the InP substrate. The influence of In_0.18Ga_0.82As buffer layer thickness and epilayer’s growth temperature on crystalline quality of InAs_0.6P_0.4 epilayer was characterized by Scanning electron microscopy, X-ray diffraction, Hall measurements, Transmission electron microscopy and Photoluminescence. The experimental results showed that the crystalline quality of InAs_0.6P_0.4 epilayers could be greatly improved by optimizing the In_0.82Ga_0.18As buffer layer thicknesses and the InAs_0.6P_0.4 epilayer’s growth temperatures. It was found that, when In_0.82Ga_0.18As buffer layer thickness was 100 nm and InAs_0.6P_0.4 epilayer’s growth temperature was 580 °C, the InAs_0.6P_0.4 epilayer exhibited the best crystalline quality and properties.     

InAs/GaAs和InAs/InxGa1-xAs/GaAs纳米线异质结构的生长研究

利用金辅助金属有机化学气相沉淀法(MOCVD)在GaAs(111)B衬底上分别制备了InAs/GaAs和InAs/In _{x Ga1-xAs/GaAs(0≤x≤1)纳米线异质结构.实验结果显示,直接生长在GaAs纳米线上的InAs纳米线生长方向杂乱或者沿着GaAs纳米线侧壁向衬底方向生长,生长的含有In x Ga1-xAs组分渐变缓冲段的InAs/In x Ga1-x关键词： 纳米线异质结构 xGa1-xAs')" href="#">InxGa1-xAs 组分渐变缓冲层 金属有机化学气相沉淀法}     

Influence of thermal annealing duration of buffer layer on the crystalline quality of In0.82Ga0.18As grown on InP substrate by LP-MOCVD

In_0.82Ga_0.18As epilayers were grown on InP substrates using a two-step growth technique by LP-MOCVD. A homogeneous low-temperature (450 °C) In_0.82Ga_0.18As buffer layer was introduced to improve the crystalline quality of epilayers. The influence of low-temperature buffer layer deposition condition, such as thermal annealing duration, on the crystalline quality of the In_0.82Ga_0.18As epilayer was investigated. Double-crystal X-ray diffraction measurement, Hall measurement, and Raman scattering spectrum were used to evaluate the In_0.82Ga_0.18As epilayers. Atomic force microscope was used to study the surface morphology. It is found that the In_0.82Ga_0.18As epilayer, with buffer layer thermal annealing for 5 min, exhibits the best crystalline quality. The change of the surface morphology of the buffer layer after thermal annealing treatment was suggested to explain the phenomenon.     

Lpe growth method possibilities in A3B5 semiconductors preparation

Pre-diffusion limited technique of liquid phase epitaxy is used for preparation of quaternary solid solution Ga _x In_1−x As _y P_1−y and binary InP. Surface morphology of the layers prepared at this condition has been compared with those prepared by conventional LPE. Quaternary strained layers with composition near to Ga_0.21In_0.79As_0.75P_0.25 were grown with perpendicular lattice mismatch up to 1.6% in compression, on the InP substrates of (100) orientation. The used epitaxial technique has been modified for perspective attempt to heal the growth interfaces. Modification was tested by InP growth. Presented at the 6th Joint Seminar “Development of Materials Science in Research and Education”, Karlštejn, Czech Republic, 17–19 September 1996.     

应力导致InAs/In0.15Ga0.85As量子点结构中In0.15Ga0.85As阱层的合金分解效应研究

利用固源分子束外延技术，在In_0.15Ga_0.85As/GaAs量子阱生长了两个InAs/In_0.15Ga_0.85As量子点(DWELL)样品.通过改变其中一个InAs DWELL样品中的In_0.15Ga_0.85As阱层的厚度和生长温度，获得了量子点尺寸增大而且尺寸分布更均匀的结果.结合光致发光光谱(PL)和压电调制光谱(PzR)实验结果，发现该样品量子点的光学性质也同时得到 关键词： 合金分解效应 0.15Ga_0.85As量子点')" href="#">InAs/In_0.15Ga_0.85As量子点 光致发光光谱 压电调制光谱     

Electromodulation spectroscopy of In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum wells

In_0.53Ga_0.47As/In_0.53Ga_0.23Al_0.24As quantum wells (QWs) of various widths have been grown by molecular beam epitaxy on the InP substrate and investigated by electromodulation spectroscopy, i.e. photoreflectance (PR) and contactless electroreflectance (CER). The optical transitions related to the QW barrier and the QW ground and excited states have been clearly observed in PR and CER spectra. The experimental QW transition energies have been compared with theoretical predictions based on an effective mass formalism model. A good agreement between experimental data and theoretical calculations has been observed when the conduction band offset for the In_0.53Ga_0.47As/In_0.53Ga_0.23Al_0.24As interface equals 60%. In addition, it has been concluded that the conduction band offset for the In_0.53Ga_0.23Al_0.24As/InP interface is close to zero. The obtained results show that InGa(Al)As alloys are very promising materials in the band gap engineering for structures grown on InP substrate.     

A simple model for optimization design of high performance In1−x−y Ga y Al x As strained MQW DFB lasers

It is well known that complex rate equations and the couple wave equation have to be solved by the method of iteration in the simulation of multi-quantum well (MQW) distributed feedback Bragg (DFB) lasers, and a long CPU time is needed. In this paper, from the oscillation condition of lasers, we propose a simple and fast model for optimization of In_1–x–y Ga _y Al _x As strained MQW DFB lasers. The well number and the cavity length of 1.55 m wavelength In_1–x–y Ga _y Al _x As MQW DFB lasers are optimized using the model. As a result, the simple model gives almost the same results as the complex one, but 90% CPU time can be saved. In addition, a low threshold, high maximum operating temperature of 550–560 K, and high relaxation oscillation frequency of over 30 GHz MQW DFB laser is presented.     

Energy band gaps for the GaxIn1−xAsyP1−y alloys lattice matched to different substrates

A pseudopotential formalism within the virtual crystal approximation in which the effects of composition disorder are involved is applied to the Ga_xIn_1−xAs_yP_1−y quaternary alloys in conditions of lattice matching to GaAs, InP and ZnSe substrates so as to predict their energy band gaps. Very good agreement is obtained between the calculated values and the available experimental data for the alloy lattice matched to InP and GaAs. The alloy is found to be a direct-gap semiconductor for all y compositions whatever the lattice matching to the substrates of interest. The (Γ→Γ) band-gap ranges and the ionicity character are found to depend considerably on the particular lattice-matched substrates suggesting therefore that, for an appropriate choice of y and the substrate, Ga_xIn_1−xAs_yP_1−y could provide more diverse opportunities to obtain desired band gaps, which opens up the possibility of discovering new electronic devices with special features and properties.     

Elastic constants and mechanical stability of InxAl1 − xAsySb1 − y lattice-matched to different substrates

Based on a pseudopotential approach under the virtual crystal approximation, the elastic modulus of In_xAl_1???xAs_ySb_1???y quaternaries lattice-matched to InP, GaSb and InAs substrates has been investigated. Our findings show a reasonably good accord with experiment. The dependence of the elastic features of interest on the indium concentration x shows a monotonic behaviour when In_xAl_1???xAs_ySb_1???y is lattice-matched to InP substrate. In that case, the elastic constants have larger values and the material system of interest becomes less harder and its rigidity becomes weaker. The mechanical stability criteria is verified in terms of elastic constants and shows that In_xAl_1???xAs_ySb_1???y is mechanically stable for each x and substrate being considered here. The change in indium content x and the substrate is found to have no much effect on both the Poisson ratio and machinability. The present study showed that a proper choice of the indium composition x and substrate may provide more diverse opportunities as regards the elastic modulus of In_xAl_1???xAs_ySb_1???y.     

Simulation of temperature-dependent material parameters and device performances for GaInAsSb thermophotovoltaic cell

Temperature-dependent material parameters and device performances of Ga_xIn_1−xAs_1−ySb_y TPV cells applied in low temperature (800–1200 °C) radiators are simulated using the PC-1D. As is well known, the optimum bandgap (E_g) decreases towards lower radiator temperatures. So far, the lowest achievable E_g of Ga_xIn_1−xAs_1−ySb_y at 300 K is 0.5 eV. We mainly considering the Ga_0.8In_0.2As_0.18Sb_0.82 (E_g = 0.5 eV) TPV cell. The effects of doping concentration and recombination mechanisms of the emitter layer on photovoltaic conversion efficiencies (η_cel) are analyzed in detail, and η_cel can be improved by optimizing doping concentration and suppressing carrier recombination. The effects of GaSb window layer on η_cel are also presented. It shows the type-II energy-band alignment GaSb(window)/GaInAsSb(emitter) heterostructure affect η_cel mainly through V_oc. For the first time, the effects of operating temperatures on device performances are analyzed based on temperature-dependent material parameters, and the temperature coefficients of the device performances are presented.     

双δ掺杂In0.65Ga0.35As/In0.52Al0.48As赝型高迁移率晶体管材料子带电子特性研究

研究了基于InP基的In_0.65Ga_0.35As/In_0.52Al_0.48As赝型高迁移率晶体管材料中纵向磁电阻的Shubnikov-de Haas(SdH)振荡效应和霍耳效应，通过对纵向磁电阻SdH振荡的快速傅里叶变换分析，获得了各子带电子的浓度，并因此求得了各子带能级相对于费米能级的位置.联立求解Schrdinger方程和Poisson方程，自洽计算了样品的导带形状、载流子浓度分布以及各子带能级和费米能级位置.理论计算和实验结果很好符合.实验和理论计算均表明，势垒层的掺杂电子几乎全部转移到了量子阱中，转移率在95%以上. 关键词： SdH振荡 二维电子气 FFT分析 自洽计算     

两个子带占据的In0.53Ga0.47As/In0.52Al0.48As量子阱中填充因子的变化规律

研究了低温(15K)和强磁场(0—13T)条件下, InP基In_053Ga_047As/In_052Al_048As量子阱中电子占据两个子带时填充因子随磁场的变化规律.结果表明,在电子自旋分裂能远小于朗道能级展宽的情况下,如果两个子带分裂能是朗道分裂能的整数倍时,即ΔE₂₁=kω_c(其中k为整数),填充因子为偶数;当两个子带分裂能为朗道分裂能的半奇数倍时,即ΔE₂₁=(2k+1)ω_c/2,填充因子出现奇数. 关键词： 053Ga_047As/In_052Al_048As量子阱')" href="#">In_053Ga_047As/In_052Al_048As量子阱 填充因子 磁输运     

Numerical analysis of the short-circuit current density in GaInAsSb thermophotovoltaic diodes

In this paper, a simulation and analysis on the short-circuit current density (J_sc) of the P-GaSb window/P-Ga_xIn_1−xAs_1−ySb_y emitter/N-Ga_xIn_1−xAs_1−ySb_y base/N-GaSb substrate structure is performed. The simulations are carried out with a fixed spectral control filter at a radiator temperature (T_rad) of 950 °C, diode temperature (T_dio) of 27 °C and diode bandgap (E_g) of 0.5 eV. The radiation photons are injected from the front P-side. Expressions for minority carrier mobility and absorption coefficient of Ga_xIn_1−xAs_1−ySb_y semiconductors are derived from Caughey–Thomas and Adachi’s model, respectively. The P-Ga_xIn_1−xAs_1−ySb_y emitter with a much longer diffusion length is adopted as the main optical absorption region and the N-Ga_xIn_1−xAs_1−ySb_y base region contribute little to J_sc. The effect of P-GaSb window and P-Ga_xIn_1−xAs_1−ySb_y emitter region parameters on J_sc is mainly analyzed. Dependence of J_sc on thickness and carrier concentration of the window are analyzed; these two parameters need to be properly selected to improve J_sc. Contributions from the main carrier recombination mechanisms in the emitter region are considered; J_sc can be improved by suppressing the carrier recombination rate. Dependence of J_sc on the carrier concentration and layer thickness of the emitter P-region are also analyzed; these two parameters have strong effect on J_sc. Moreover, adding a back surface reflector (BSR) to the diode can improve J_sc. The simulated results are compared with the available experimental data and are found to be in good agreement. These theoretical simulations help us to better understand the electro-optical behavior of Ga_xIn_1−xAs_1−ySb_y TPV diode and can be utilized for performance enhancement through optimization of the device structure.     

Effect of compressive and tensile stresses in GaMnAs layers on their magnetic properties

The effect of elastic stresses (compressive, tensile) on the magnetic properties of epitaxial GaMnAs layers prepared by laser deposition of solid-state targets in a gas atmosphere on different buffer sublayers (In _x Ga_{1 − x} As and In _x Ga_{1 − x} P) and substrates (GaAs, InP) has been investigated. It has been established from the investigations of magnetic-field dependences of the Hall resistance that all layers exhibit ferromagnetic properties with the Curie temperature ∼50 K. It has been shown that, in the case of tensile stresses in GaMnAs layers (In _x Ga_{1 − x} As and In _x Ga_{1 − x} P buffers and InP substrate), the anomalous Hall effect shape demonstrates a predominant orientation of the easy-magnetization axis in the growth direction, unlike the GaMnAs layers prepared on a GaAs substrate (with compressive stresses), which demonstrate the predominance of the component of the magnetization vector in the layer plane.     

Evidence by Raman scattering on In1−xGaxAsyP1−y of the two-mode behaviour of In1−xGaxP

We report the Raman scattering study of optical vibrations in indium rich In_1?xGa_xAs_yP_1?y epitaxial layers grown on InP. We evidence the splitting of the LO line of InP even for very small x and demonstrate it is due to the presence of gallium in the samples. These results lead us to ascribe to In_1?xGa_xP a somewhat modified two-mode behaviour and to In_1?xGa_xAs_yP_1?y a four-mode behaviour.     

Highly strained InxGa(1−x)As−InyAl(1−y)As (x>0.8,y<0.3) layers for short wavelength QWIP and QCL structures grown by MBE

Highly strained quantum cascade laser (QCL) and quantum well infrared photodetector (QWIPs) structures based on In_xGa_(1−x)As−In_yAl_(1−y)As (x>0.8,y<0.3) layers have been grown by molecular beam epitaxy. Conditions of exact stoichiometric growth were used at a temperature of 420°C to produce structures that are suitable for both emission and detection in the 2–5 μm mid-infrared regime. High structural integrity, as assessed by double crystal X-ray diffraction, room temperature photoluminescence and electrical characteristics were observed. Strong room temperature intersubband absorption in highly tensile strained and strain-compensated In_0.84Ga_0.16As/AlAs/In_0.52Al_0.48As double barrier quantum wells grown on InP substrates is demonstrated. Γ–Γ intersubband transitions have been observed across a wide range of the mid-infrared spectrum (2–7 μm) in three structures of differing In_0.84Ga_0.16As well width (30, 45, and 80 Å). We demonstrate short-wavelength IR, intersubband operation in both detection and emission for application in QC and QWIP structures. By pushing the InGaAs–InAlAs system to its ultimate limit, we have obtained the highest band offsets that are theoretically possible in this system both for the Γ–Γ bands and the Γ–X bands, thereby opening up the way for both high power and high efficiency coupled with short-wavelength operation at room temperature. The versatility of this material system and technique in covering a wide range of the infrared spectrum is thus demonstrated.     

Influence of stoichiometry on the luminescent properties of InAs quantum dots grown on a heterostructure

We report photoluminescence (PL) spectra of InP/In_xGa_1-xAs/InAs/InP dot-in-a-well structures grown by MOVPE, with different compositions of the ternary layer. Measurements with atomic force microscopy showed that the largest quantum dot (QD) height is obtained when the InAs QDs are grown on the In_xGa_1-xAs layer with a mismatch of 1000 ppm, and the height decreases as the mismatch departs from this value. PL spectra of the QDs showed an asymmetric band, which involves transitions between dot energy levels and can be deconvoluted into two peaks. The highest energy PL peak of this band was observed for the sample with the QDs grown on top of the lattice-matched In_xGa_1-xAs layer and it shifted to lower energies for strained samples as the degree of mismatch increased. Theoretical calculations of the energy levels of the entire structure were used to interpret the obtained PL spectra and determine the possible detection tunability range.     

A convenient band-gap interpolation technique and an improved band line-up model for InGaAlAs on InP

The band-gap energy and the band line-up of InGaAlAs quaternary compound material on InP are essential information for the theoretical study of physical properties and the design of optoelectronics devices operating in the long-wavelength communication window. The band-gap interpolation of In_1−x−y Ga _x Al _y As on InP is known to be a challenging task due to the observed discrepancy of experimental results arising from the bowing effect. Besides, the band line-up results of In_1−x−y Ga _x Al _y As on InP based on previously reported models have limited success by far. In this work, we propose an interpolation solution using the single-variable surface bowing estimation interpolation method for the fitting of experimentally measured In_1−x−y Ga _x Al _y As band-gap data with various degree of bowing using the same set of input parameters. The suggested solution provides an easier and more physically interpretable way to determine not only lattice matched, but also strained band-gap energy of In_1−x−y Ga _x Al _y As on InP based on the experimental results. Interpolated results from this convenient method show a more favourable match to multiple independent experiment data sets measured under different temperature conditions as compared to those obtained from the commonly used weighted-sum approach. On top of that, extended framework of the model-solid theory for the band line-up of In_1−x−y Ga _x Al _y As/InP heterostructure is proposed. Our model-solid theory band line-up result using the proposed extended framework has shown an improved accuracy over those without the extension. In contrast to some previously reported works, it is worth noting that the band line-up result based on our proposed extended model-solid theory has also shown to be more accurate than those given by Harrison’s model.     

High-temperature operation of AlGaInAs/InP lasers1994

We discuss the design of uncooled lasers which minimizes the change in both threshold current and slope efficiency over the temperature range from–40 to +85°C [1]. To prevent carrier overflow under high-temperature operation, the electron confinement energy is increased by using the Al _x Ga _y In_1–x–y As/InP material system [1] instead of the conventional Ga _x In_1–x As _y P_1–y /InP material system. Experimentally, we have investigated strained quantum well lasers with three different barrier layers and confirmed that the static and dynamical performance of the lasers with insufficient carrier confinement degrades severely under high-temperature operation [2]. With an optimized barrier layer, the Al _x Ga _y In_1–x–y As/InP strained quantum well lasers show superior hightemperature performance, such as a small drop of 0.3 dB in slope efficiency when the heat sink temperature changes from 25 to 100°C [3], a maximum CW operation temperature of 185°C [4], a thermally-limited 3-dB bandwidth of 13.9 GHz at 85°C [2], and a mean-time-to-failure of 33 years at 100°C and 10 mW output power [5].     

超晶格中GaAs/InGaAs界面与InGaAs/GaAs界面的特性差异

In_xGa_1-xAs缓冲层上生长In_yGa_1-yAs/GaAs超晶格（x＜y）．阱层处于压缩应变，垒层处于伸张应变，其厚度均小于Mathews-Blakeslee（M-B）平衡理论计算的临界厚度．透射电子显微镜及俄歇电子能谱、二级离子质谱测试发现，GaAs/In_yGa_1-yAs界面铟组分过渡区比In_yGa_1-yAs/GaAs界面铟组 关键词：