Impurity states in GaAs:O

The ground state energy E, wavefunction, and wavevector dependence of the probability density of GaAs:O are presented. E is found to be 0.785 eV from the bottom of the conduction band.     

Diffusion along the Grain Boundaries in Crystals with Dislocations

A generalization of the Fisher model of the grain boundary diffusion is suggested, which takes into account the diffusion along short circuit diffusion paths (i.e., dislocations) in the bulk of crystalline grains. For the B-regime of the grain boundary diffusion, three different penetration modes have been found: at the short times the penetration depth of the element diffusing along the grain boundary is given by the Whipple solution of the Fisher model, but with the pipe diffusion coefficients along the dislocation cores instead of the volume diffusivities; at the intermediate times the penetration depth is a weak function of time, and at the large times the penetration depth again increases with time according to the Whipple solution, however, the rate of this increase is much smaller than in the initial period of time. The applications of the model for diffusion in nanomaterials are discussed.     

Dislocations in GaAs single crystals grown by the Czochralski method

The influence was studied of growth conditions on the dislocation density in gallium arsenide single crystals grown by the Czochralski method from a gallium-enriched melt. Etching in a solution of 1 part cone. HNO₃ and 2 parts H₂O served to determine the dislocation density across and along a single crystal. The dislocation density along the crystal was found to depend mainly on the angle of crystal diameter increase.     

Impurity state electroabsorption studies in oxygen-doped GaAs

Electroabsorption measurements at 300 K made within the band gap on high resistivity GaAs:O are reported. For a crystal with the Fermi level at 0.54 eV, major structure has been detected at 0.52, 0.57, 0.67, 0.75, 0.87, 0.93, 1.03, 1.12, 1.25, 1.36, and 1.39 eV. The 0.67 eV peak appears only in the second harmonic spectrum, indicating no change in permanent dipole for this transition. Polarized light, lock-in amplifier phase angle, and applied field variation data are presented.     

Impurity conduction and magnetoresistance in lightly dopedn-type GaAs

Measurements of the resistivity and magnetoresistance of epitaxially grownn-type GaAs (N _D ~ 1–2 × 10¹⁵ cm^–3) at 4.2 K and below are reported. The hopping resistivity ₃ depends onN _D according to ₃= ₀ exp (1.88/N _D ^1/3 a) in agreement with predictions of percolation theory, wherea is the Bohr radius of the impurity ground state. The experimentally obtained preexponential factor ₀ is very close to a recent theoretical prediction, which was derived from the computation of the topology of an infinite cluster. In magnetic fields below 1.3T the resistivity is found to be proportional to exp ,t having a value of 0.06 in disagreement with a recent theoretical calculation oft=0.04. In the high magnetic field region above 3T the data are described by exp [q ( ² a _B N _D)^–1/2], where is the characteristic magnetic length anda _B is the magnetic field dependent Bohr radius. From the experiments a value ofq=0.68 is deduced, while the theory predictsq=0.98.     

基于杂质光伏效应的镍掺杂对砷化镓太阳电池性能的影响

利用杂质光伏效应能够使太阳电池充分利用那些能量小于禁带宽度的太阳光子,从而提高电池的转换效率.为了更好地利用杂质光伏效应提高砷化镓太阳电池的转换效率,本文利用数值方法研究在砷化镓太阳电池中掺入镍杂质以形成杂质光伏太阳电池,分析掺镍对电池的短路电流密度、开路电压以及转换效率的影响;同时,探讨电池的陷光结构对杂质光伏太阳电池器件性能的影响.结果表明:利用杂质光伏效应掺入镍杂质能够增加子带光子的吸收,使得电池转换效率提高3.32%;转换效率的提高在于杂质光伏效应使电池的红外光谱响应得到扩展;另外,拥有良好的陷光结构是取得好的杂质光伏效应的关键.由此得出:在砷化镓太阳电池中掺镍形成杂质光伏太阳电池是一种能够提高砷化镓太阳电池转换效率的新方法.     

Influence Des Dislocations Sur La Conductibilite Thermique De GaAs

The dislocation-phonon interaction has been experimentally studied on GaAs:Te single crystals and discussed using the Klemens' theory. A controlled heat treatment allows to distinguish this specific mechanism even for non-stoichiometric material.     

Diffusion coefficient of hot electrons in GaAs

The longitudinal and transverse diffusion coefficient of hot electrons in GaAs at a lattice temperature of 300 K has been calculated by the Monte Carlo technique. The calculations showed that drift velocity and diffusion coefficient of hot electrons in GaAs can be fitted to available experimental data if the three-valley Γ-L-X model is used. The estimates of some parameter values of GaAs conduction band have been made.     

Impurity conduction and magnetoresistance in lightly dopedn-type GaAs

Measurements of the resistivity and magnetoresistance of epitaxially grownn-type GaAs (N _D ~ 1–2 × 10¹⁵ cm^–3) at 4.2 K and below are reported. The hopping resistivity ( \fractal⁴ N_D )\left( {\frac{{ta}}{{\lambda ^4 N_D }}} \right) ,t having a value of 0.06 in disagreement with a recent theoretical calculation oft=0.04. In the high magnetic field region above 3T the data are described by exp [q ( ² a _B N _D)^–1/2], where is the characteristic magnetic length anda _B is the magnetic field dependent Bohr radius. From the experiments a value ofq=0.68 is deduced, while the theory predictsq=0.98.     

Impurity bands in Ga1-xAlxAs/GaAs quantum wells

We calculate the Density-of-States (DOS) for electrons bound to impurities in a thin sheet inside a Ga_1-xAl_xAs/GaAs quantum well. Impurities are considered at the center, midway to the interface and at the interface of the GaAs layer. It is shown that for reasonable impurity concentrations an impurity band appears separated from the lowest subband. The bandwidth is comparable with that obtained due to diagonal disorder assuming a uniform distribution inside the whole well.     

Model of Formation of Discrete Dislocations of the Thermoelastic Martensitic Transformation

Physics of the Solid State - The problem of the transition of a pre-martensite nanostructure of a SME crystal to a structure of discrete dislocation loops of the martensitic transformation is...     

Impurity cyclotron resonance in InGaAs/GaAs superlattice and InGaAs/AlAs superlattice grown on GaAs substrates

Various temperature measurements of cyclotron resonance (CR) under pulsed ultra-high magnetic field up to 160 T were carried out in InGaAs/GaAs superlattice (SL) and InGaAs/AlAs SL samples grown by molecular beam epitaxy on GaAs substrates. Clear free-electron CR and impurity CR signals were observed in transmission of CO₂ laser with wavelength of 10.6 μm. A binding energy of impurities in these SLs was roughly estimated based on the experiment as result, and we found it was smaller than the previous experimental result of GaAs/AlAs SLs and theoretical calculation with a simple model.     

Two-Time Diffusion Process in the Porous Medium

We find that there are two time scales t and ε ln t in the asymptotic behaviour of diffusion process in the porous medium, which give us a new insight to the anomalous dimension in this problem. Further we construct an iterative method to calculate the anomalous dimension and obtain an improved result.     

Diffusion of deuterium in GaAs from a molecular gas source

It is shown for the first time that deuterium can diffuse into GaAs from a gaseous source. Experiments performed at 500° C show two-component diffusion profiles with diffusion coefficients in the range 10^–15–4×10^-1cm²s^–1 depending on the conductivity type of the samples. These diffusion coefficients are considerably lower than those determined after RF plasma hydrogenation. Such a slow diffusion process is related to the reaction of molecular deuterium with the sample surface leading to the dissociation of the deuterium molecules.     

Formation of gallium microinclusions in GaAs single crystals

In this report we analyze the causes of gallium microinclusion formation in gallium arsenide single crystals. We present a model in which microinclusions result from the decomposition of a supersaturated solid solution. From experimental data available in the literature and calculated kinetic parameters of the model we demonstrate that microinclusion formation in bulk single crystals follows the mechanism of homogeneous nucleation and Brownian coalescence of precipitated liquid gallium metal.Translated from Izvestiya Vysshikh Uchbenykh Zavedenii, Fizika, No. 2, pp. 32–35, February, 1988.     

Zn杂质扩散诱导AlGaInP/GaInP量子阱混杂

杂质扩散诱导量子阱混杂技术可用于制作腔面非吸收窗口,提高大功率半导体激光器的输出功率.以Zn2As2为扩散源,采用闭管扩散方式,在550℃下对650 nm半导体激光器的外延片进行了一系列Zn杂质扩散诱导量子阱混杂的实验.实验发现,随着扩散时间从20～120 min,样品光致发光(PL)谱蓝移偏移增加,峰值波长蓝移53 nm;当扩散时间超过60 min后,样品的PL谱中不仅出现了常见的蓝移峰,同时还出现了红移峰,峰值波长红移32 nm.分析表明PL谱蓝移来自Zn扩散引起的AlGaInP/GaInP间的量子阱混杂;红移来自Zn杂质扩散对样品中Ga0.51In0.49P缓冲层的影响.还研究了扩散温度(550℃)和扩散时间对样品晶体品质的影响,并在理论上计算了AlGaInP/GaInP量子阱混杂巾的Al-Ga的互扩散系数.     

Impurity lattice sites after implantation of Te and Sb in GaAs: Search for the DX centre

¹¹⁹Sn Mössbauer Spectroscopy has been applied to study the nearest environment of radioactive^119mTe and¹¹⁹Sb atoms implanted into GaAs. After a low-dose implantation and annealing above 300°C the impurity atoms are found at As sites. High-dose implantation and annealing above 600°C results in the population of at least two additional sites; these are clearly different for Te and Sb. No evidence is found for the population of DX-centres. A likely possibility is the formation of coherent Ga₂Te₃ precipitates.