Epitaxial growth and characterization of InAs/GaSb and InAs/InAsSb type-II superlattices on GaSb substrates by metalorganic chemical vapor deposition for long wavelength infrared photodetectors

We report on the epitaxial growth and characterization of InAs/GaSb and InAs/InAsSb type-?? superlattices (T2SLs) on GaSb substrates by metalorganic chemical vapor deposition. For InAs/GaSb strained T2SLs, interfacial layers were introduced at the superlattice interfaces to compensate the tensile strain and hence to improve the overall material quality of the superlattice structures. The optimal morphology and low strain was achieved via a combined interfacial layer scheme with 1 monolayer (ML) InAsSb+1 ML InGaSb layers. In contrast, the InAs/InAsSb strain-balanced T2SLs allow for a relatively easy strain management and simple precursor flow switching scheme while maintaining device-quality materials. Surface root mean square roughness of 0.108 nm and a nearly zero net strain were obtained, with effective bandgaps of 147 and 94 meV determined for two sets of InAs/InAsSb strain-balanced T2SLs.     

Studies on the lattice match and strain in the epitaxial growth of III – V alloys on inas and GaSb substrates

The compositional conditions to deposit the epitaxial films of III – V materials lattice matched to InAs and GaSb substrates have been investigated and the results are presented in the form of charts. The validity of our theoretical predictions has been tested by comparing with the available experimental results. Strain in the Ga_xIn_{1 − x}As_ySb_{1 − y} quaternary alloy has been visualised as three-dimensional perspective plots.     

GaSb薄膜生长的RHEED研究

采用分子束外延技术,在GaAs衬底上生长GaSb薄膜时,利用反射式高能电子衍射仪(RHEED)对衬底表面清洁状况、外延层厚度等进行在线监控.通过RHEED讨论低温缓冲层对GaSb薄膜表面结构和生长机制的作用,可以估算衬底温度,并能计算出薄膜的生长速率.实验测量GaSb的生长周期为1.96s,每秒沉积0.51单分子层.低温缓冲层提高了在GaAs衬底上外延GaSb薄膜的生长质量.     

The dependence of surface morphology of GaSb- and AlxGa1–xSb epitaxial layers on the conditions of LPE growth

The present work shows the dependence of surface morphology of the GaSb and Al_xGa_1–xSb epitaxial layers on the conditions of LPE growth. It is found that for LPE growth at 500 °C a supersaturation of 5—10 °C and a cooling rate of 0.24—0.4°C/min for GaSb epitaxial layers and 0.8—1.2 °C/min for Al_xGa_1–xSb epitaxial layers is necessary to obtain a flat and smooth surface.     

Growth of Heterostructures Based on InAs–AlxGa1–xSb

It is reported on the liquid phase epitaxial (LPE) growth of heterostructures on the base of InAs–Al_xGa_1–xSb. The paper includes the investigation of epitaxial layers of Al_xGa_1–xSb alloys on InAs substrates and results of experiments for the determination of optimum growth regimes.     

Critical thickness of the 2-dimensional to 3-dimensional transition in GaSb/GaAs(001) quantum dot growth

The phase transformation from planar to quantum dot growth is driven by strain energy reduction at the cost of surface energy. By calculating and comparing the strain energies of monolayer thick GaSb and InAs films on GaAs(001), a critical thickness for the 2-dimensional to 3-dimensional phase transformation of about 1.2 ML was derived for the GaSb/GaAs quantum dot system. This value is in agreement with the direct observation of the effectively deposited amount of material using cross-sectional scanning tunneling microscopy. Deviating experimental literature values can be traced back to the neglect of the Sb-for-As exchange process.     

A difference between initial growth stages of the AlGaAs/GaAs and GaAs/AlGaAs heterostructures produced by contact replacement of solutions

The method of liquid epitaxial growth of GaAs/AlGaAs/GaAs heterostructures when the change of solutions occurs due to pushing off one melt by another is discussed. It has been shown theoretically and experimentally that the initial stages of film growth after the change of the binary Ga As melt on the ternary Al Ga As melt differ from that when the Ga As solution pushes off the Al Ga As liquid. The difference is caused by the inequality of the diffusion coefficients of As and Al in a multicomponent Al Ga As liquid (D_Al > D_As). As a result, the growth of an AlGaAs film begins immediately in the case when the Al Ga As solution pushes off the Ga As liquid but in the opposite case the dissolution of an underlying AlGaAs solid is unavoidable and depends little on degree of a saturation of the Ga As washing solution. These peculiarities must be taken into account in discussions of abruptness and other properties of LPE-grown AlGaAs/GaAs and GaAs/AlGaAs heterojunctions.     

GaSb/InAs heterojunctions grown by MOVPE: Effect of gas switching sequences on interface quality

The GaSb/InAs interface can be grown in two quite different ways either with In and Sb atoms forming the interface “InSb-like” or Ga and As atoms forming the interface “GaAs-like”. This is a result of both the Group III and Group V atoms changing at the interface. Different interfaces have been achieved in GaSb/InAs heterojunctions grown by atmospheric MOVPE using different gas switching sequences and the consequent changes in the electrical behaviour have been assessed using low field magnetotransport measurements. The results range from very poor (“GaAs-like”) to excellent (a particular “InSb-like”) interface. A further comparison is made to a previously used growth sequence for these structures. The effect of pauses during the interface sequence has also been investigated.     

Thin-layer GaInSbAsPBi/GaSb heterostructures obtained from liquid phase in a temperature-gradient field

The results of growing thin epitaxial GaInSbAsPBi layers on a GaSb substrate from a liquid bismuth-containing zone in a temperature-gradient field are discussed. The composition and properties of GaInSbAsPBi/GaSb heterostructures are investigated.     

Characteristics of Growing of Heterostructures in the System GaSb–AlSb

In the present work, some factors are pointed out hindering the growing of good-quality epitaxial layers and heterostructures in the system GaSb–AlSb. Their influence is studied on the morphology of the surface and the cleavage of the epitaxial structures GaSb–Ga_1–xAl_xSb. The characteristics of the optimal technological regime are shown.     

无位错Te-GaSb(100)单晶抛光衬底的晶格完整性

采用液封直拉(LEC)法批量生长的直径2英寸(1英寸=2.54 cm)n型Te-GaSb(100)单晶的位错腐蚀坑密度(EPD)通常低于300 cm^-2,达到无位错水平。本文利用X射线摇摆曲线以及倒易空间图(RSM)对这种GaSb单晶抛光衬底的晶格完整性和亚表面损伤情况进行了分析表征,结果表明经过工艺条件优化的化学机械抛光处理,GaSb单晶衬底表面达到原子级光滑,不存在亚表面损伤层。利用分子束外延在这种衬底上可稳定生长出高质量的Ⅱ类超晶格外延材料并呈现出优异的红外探测性能。在此基础上,对CaSb衬底材料的物性、生长制备和衬底加工条件之间的内在关系进行了综合分析。     

X-ray diffraction studies of interdiffusion in InP?GaP powder blends

Interdiffusion in the InP GaP solid solution system is investigated by means of X-ray diffraction of annealed powder blends. An activation energy of Q = (3.15 ± 0.3) eV for the interdiffusion process in the temperature interval 650… 725 °C was found. Diffusion parameters obtained by means of this method for InP GaP and InAs GaAs are discussed on the basis of lattice and atomic characteristics.     

Growth and properties of GaSb, Ga1-xInxSb and Ga1-xAlxSb epilayers by MOCVD

GaSb-based compound semiconductors are suitable materials for low-noise avalanche photo-diodes(APD's) and long wavelength laser diodes and photodetectors. In this paper, we review the metal organic chemical vapor deposition (MOCVD) growth conditions and the properties of GaSb, GaInSb and AlGaSb epitaxial layers, including the effects of III/V ratio, growth temperature, pressure and growth rate on electrical quality, optical properties, surface morphology and solid distribution coefficients.     

Application of the iodide synthesis to the preparation of indium arsenide bulk crystals and epitaxial layers

Bulk crystals and epitaxial layers have been prepared from iodidely synthesized InAs. Their parameters have been studied and compared with those of high-temperature synthesized InAs. The synthesis mixture composition substantially effects the electrical parameters of the samples. Iodine is supposed to be a donor-acting impurity in iodidely synthesized InAs.     

Molecular beam epitaxy of GaSb/AlxGa1 − xSb quantum well structures

Molecular beam epitaxy (MBE) is used to grow GaSb/Al_xGa_{1 − x}Sb quantum well (QW) structures on GaSb(001) substrates using both Sb₂ and Sb₄ molecules. While the optoelectronic properties of thick GaSb epitaxial layers are significantly affected by the type of molecule used, no influence is noted on the QW photoluminescence properties. It is shown that MBE allows a very precise and reproducible control of the QW structure parameters such as QW widths for which monolayer precision is obtained. Through the variation of the QW associated PL energy as a function of the growth temperature, the occurrence of a surface segregation-like phenomenon is evidenced. However, this effect is rather weak so that a good estimation of the valence band offset through the PL energy variation with the QW width can be made. Moreover, the QW width for which the Γ-L crossover occurs is very precisely determined.     

Liquid Phase Epitaxy of SiC in the System Tb?Si?SiC by Temperature Gradient Zone Melting (II). Liquid Phase Epitaxy of SiC from Tb?Si Solvent

The liquid phase epitaxy of SiC by the gradient temperature zone melting in the Si Tb solvent is studied. A new variant of this growth method is presented. The comparison of the new variant with the previous one shows that the new variant allows for epitaxial layers with significant better electrophysical properties. It is easier and can be carried out at lower temperature.     

Growth of InAsSb/InAs MQWs on GaSb for mid-IR photodetector applications

We report the OMVPE growth and characterization of InAsSb/InAs strain balanced multiple quantum wells lattice-matched to GaSb substrates for potential application as mid-infrared detectors for wavelengths beyond 4 μm$\mathrm{\mu }\mathrm{m}$. Detailed transmission electron microscopy measurements were performed to evaluate the degree of Ga and Sb intermixing at the GaSb/InAsSb and InAs/InAsSb interfaces. Photoluminescence emission up to 5 μm$\mathrm{\mu }\mathrm{m}$ was observed for superlattice structures with only 15% antimony. The dependence of PL on wavelength is red shifted compared to expectations based on type I band alignment.     

Characteristics of GaSb growth using various gallium and antimony precursors

We report the epitaxial growth of GaSb using trimethylgallium (TMGa) or triethylgallium (TEGa) with trimethylantimony (TMSb), triethylantimony (TESb), or trisdimethylaminoantimony (TDMASb) in a low-pressure vertical rotating-disk reactor. Growth is kinetically limited for TMGa in the temperature range 560 to 640°C, and is mass-transport limited for TEGa in the range 525 to 640°C. A minimum V/III ratio is necessary to obtain stoichiometric GaSb, and is dependent on the pyrolysis temperature of Ga and Sb precursors. Featureless morphology is achieved for layers grown with TMGa or TEGa and TMSb, while surface defects are observed for layers grown with TEGa and TESb or TDMASb. These observations are consistent with Fourier transform infrared measurements, which indicate interactions between TEGa and TESb or TDMASb. All nominally undoped layers are p-type, with overall superior properties being obtained for layers grown with TEGa and TMSb. However, growth conditions that yield layers with the best electrical properties do not necessarily correspond to the same conditions for highest optical quality.     

Kinetic aspects in the vapour phase epitaxy of III–V compounds

Successful exploitation of the unique properties of III–V compound semiconductors has resulted in development of several new devices for optoelectronic and solid state microwave applications. These achievements, however, would not have been possible without major advances in the technology for epitaxial growth of such materials. Further improvements in device performances together with new applications of III–V compounds must be closely coupled with even more progress toward achievement of material with properties approaching the theoretical values. Chemical vapour deposition has emerged as the most common technique for epitaxial growth. Although significant improvements can be obtained through empirical methods of investigation of such processes, it is recognized that in the long run a firm fundamental understanding is essential. This realization provides the motivation for detailed, basic studies of the kinetics and thermodynamics of epitaxial growth by chemical vapour deposition. This review will examine the progress, both past and projected, in measurement and interpretation of the kinetics of vapour phase deposition of III–V epitaxial layers. The scope will be limited to near-atmospheric pressure, open flow epitaxial systems utilizing chemical transport. To date, most of the studies have concerned GaAs, GaP, InAs, InP, and their alloys. It has been demonstrated for GaAs, and for some of the other compounds as well, that, depending on the growth conditions, epitaxial deposition may proceed in two fundamentally different rate-limiting regimes. At low temperatures the rate is limited by a surface process; while at higher temperatures mass transport limitations appear to prevail. For mass-transport-limited deposition the sensitivity of the growth rate to various operating parameters can, in many cases, be predicted from theoretical considerations. Investigation of kinetically limited growth offers a path toward a fundamental understanding of the atomistic surface events that result in epitaxial growth. The progress in these areas will be discussed; in addition, experimental and theoretical tasks for future studies will be recommended.     

Transport Coefficients and Structural Principles of PbO?Ga2O3 Melt

More Precise knowledge of the growth mechanism of garnets in form of epitaxial layers or single crystals in high temperature solutions on the base of trivalent oxides Me₂O₃ in PbO B₂O₃ solvent is desirable. Data of physicochemical properties of the melts especially density, shear viscosity, and electrical conductivity and their dependence on the temperature are useful in endeavour to recognize the structural principles of oxidie melts. Therefore as a first step the binary system PbO Ga₂O₃ was investigated to understand the influence of the Ga component on a complete mixed garnet solution, for instance (Y, Sm)₃ (Fe, Ga)₅O₁₂ in PbO B₂O₃ solvent.