Growth of gallium antimonide epitaxial layers on indium arsenide substrates

In the present work the possibility is demonstrated of growing gallium antimonide epitaxial layers on indium arsenide substrates using the liquid phase epitaxial (LPE) method. The influence is nivestigated of the growth conditions on the morphology of the surface and interface of the epitaxial structures InAs GaSb. The optimum technological regimes for growth of heterostructures in the system InAs GaSb are found.     

Energy band-gap in elastic-strained heteroepitaxial layers

The effect of internal elastic stress on energy band-gap shift in the A³B⁵ heteroepitaxial layers was investigated. The possibilities to get higher accuracy of divergent beam X-ray stress determination method, designed in the scanning electron microscope (SEM), was presented. X-ray topography method in the SEM with X-ray magnification from 2 up to 10 was for the first time described. The epilayer photoluminescence (PL) peak energy shift as a function of internal elastic stress was measured on the GaInP/GaAs, GAInAsP/InP heterostructures and the influence of different factors on the accuracy of the results was discussed.     

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.     

Micromorphology and defects of non-doped gallium arsenide layers

Electron microscopy was used to study non-doped GaAs layers obtained in a chloride system Ga-AsCl₃-H₂. Electron concentrations is 10¹³–10¹⁵ cm⁻³, mobility at liquid nitrogen temprature reaches 200000 cm²/v. sec. It is shown that a fraction of the growth surface taken with (110) faces is less for films with less electron concentration. The main type of defects in pure GaAs layers is precipitates at pinning centres of growth steps. Estimations based on microdiffraction patterns and irradiation effects show that the impurity concentration in them is 10¹⁶–10¹⁹ cm⁻³. The impurity in precipitates is assumed to be electrically non-active, mainly, in interstitial positions.     

Effect of buffer layers on the dislocation structure of heteroepitaxial systems

Transmission electron microscopy (TEM) as well as X-ray topography (XRT) and X-ray diffractometry have been used for investigation of the structure of the LPE heteroepitaxial system In_0.05Ga_0.95As-In_yGa_1−yAs_1−xP_x-GaAs(111) A. A critical value of the lattice misfit has been shown to exist at the metallurgical boundary ((Δa/a)* ≈ 10⁻³) which results in the change of the film nucleation and growth mechanism as well as the change of misfit dislocations (MDs) generation mechanism. With (Δa/a)₀ > (Δa/a)* the nucleation and growth mechanism is mixed: island growth at the first stages of growth and layer-by-layer growth at large thicknesses. MDs are created in an “island film” developing a non-ordered dislocation network. The density of threading dislocations (N_d) is ∼ 10⁸ cm⁻². With (Δa/a)₀ < (Δa/a)* there is layer-by-layer mechanism of film's nucleation and growth from the very first stages of crystallization. MDs are injected into continuous layer along the inclined slip planes {111}, thus forming a regular three-dimensional grid of MDs. N_d is less than 10⁶ cm⁻² in the case. A model of dislocation structure formation in heterolayers has been proposed. Within the frame of this model the two critical values of phosphorus concentration in the quaternary melt have been quantitatively determined. These are corresponding to the change of MD generation mechanism. The expected values of N_d for (Δa/a)₀ > (Δa/a)* and (Δa/a)₀ < (Δa/a)* have been theoretically determined.     

On the scandium distribution in indium arsenide crystals grown by the Czochralski method

In this paper the behaviour of scandium in n-type monocrystalline indium arsenide grown by Czochralski method in sealed ampoule is studied. The crystals have been grown in [111] direction under different conditions: crystallization rate, As-partial pressure and scandium initial concentration in the melt. The effect of the above factors on the scandium distribution along the crystals have been investigated. Using these results and by means of the equation of normal freezing the effective Sc distribution coefficient (k) in InAs under different technological conditions has been determined. It has been found that k < 1 in all experiments. In order to find the equilibrium coefficient (k₀) at fixed growth conditions the Burton-Prim-Slichter model has been used. On the basis of Hall measurements and atomic absorption analysis of Sc-doped InAs it is concluded that connected with Sc electrically active centers behave as shallow donors, most probably monovalent ones.     

Diffuse X-ray scattering study of the temperature variation of elastic constants in indium arsenide

The elastic constants of indium arsenide have been determined in the temperature range from 80 to 750 K on n-type samples with a carrier concentration of about 8 · 10¹⁷ cm⁻³ by Wooster's method from the measurements of the thermal X-ray diffuse scattering intensities. An average decrease in the elastic constants with increasing temperature over the above mentioned temperature range is found to be about 8%.     

Investigation of GaN heteroepitaxial layers by means of the kossel effect technique

GaN heteroepitaxial layers grown on spinel substrates have been investigated by the Kossel effect technique. The excitation of GaK_α X-rays inside the crystal lattice was carried out either by means of 1.25 MeV protons or 40 KeV electrons. Both methods give similar results concerning the values of the lattice parameters and the sign of polarity. Following the proton irradiation a lattice expansion normal to the surface occurs. A comparison of our results with those of other authors shows that the growth direction is the same for {111} spinel and {0001} sapphire substrates.     

Investigation of InAs—InSb solid solution heteroepitaxial layers and structures

The results of investigations concerning the peculiarities of obtaining InAs—InAs_1−xSb_x heterostructure and of its properties revealed that the quality of epitaxial layers as well as photoelectric and electroluminescent device structure characteristics are to a great extent determined by a disagreement magnitude of heterostructure materials. — To decrease the magnitude of disagreement at the layer-substrate boundary and to achieve the composition with x > 0.1 at some distance the method of layer-by-layer growth (ANDREWS et al.) and the obtaining a graded heterojunction with optimization of component distribution along epilayer thickness seems to be promising.     

Dislocation density in pure crystals grown from melts

Physical reasons are considered which are responsible for dislocation formation in crystals grown by different ways, i. e. by Czochralski's, Stepanov's, Kyropoulos's, Verneuil's, Bridgman's, Stockbarger's methods and floating zone technique. Equations are presented allowing to evaluate the dislocation density in pure crystals prior to testing. The conditions for obtaining dislocation free crystals have been considered. The equations for dislocation density evalution have been compared with the experimental results of different authors. Thermal stresses have been proved to be the main source of dislocation formation, and the equations corresponding to this mechanism in most cases enable to predict the dislocation density with the error being a factor of 1–3.     

Mechanism of condensation of heteroepitaxial A3B5 layers pulse of moderate power

The mechanism of condensation of heteroepitaxial layers in laser deposition was studied on GaAs films on NaCl. Films were deposited in a superhigh vacuum using laser pulses of moderate power. Pulsed deposition proved to be more suitable for nucleation and growth than continuous deposition. However in this case it is important to compare the number of atoms deposited per pulse and the number of preferential adsorption centres in the substrate temperature of 310 °C. The density of dislocations in the films was about 10⁹ cm⁻². The main reasons for the dislocations are the excess of low volatile component and thermal stresses. Using a laser with quantum energy higher than the energy gap of the deposited semiconductor GaAs, which provides congruent evaporation, and making an additional deposition of As, we could reduce dislocations to 10⁷ cm⁻². A mechanism is proposed to explain the reduction of temperature in single crystal growth under laser deposition: high energy ion component of laser plasma gives rise to orienting defects on the substrate surface, and these defects determine epitaxial growth.     

Effect of electrical field on growth of gallium arsenide layers from vapour phase

The effect of electrical fields on the growth rate and morphology of gallium arsenide layers in the GaAs AsCl₃ H₂ system is investigated. The fields both parallel and perpendicular to the substrate surface are used. It is found that application of the parallel field results n increase of growth rate of (111)A face but does not change that of 2° (001). The morphology of layers grown in such a field is better than that grown without any. The application of perpendicular field results in decrease of growth rate for both crystallographic orientations, the layer morphology worthening. In both cases the effect is greater when the substrate has a negative potential. Possible mechanisms of the field influence on the growth rates of gallium arsenide layers are discussed such as: supersaturation decrease because of nucleation in vapour phase and the change in the rates of surface processes.     

The strain energy density of cubic epitaxial layers

We obtain a compact exact expression for the strain energy density of a cubic epitaxial medium in the limit of linear elasticity theory. Only the result for 001 is identical to the isotropic case: the greatest departure from isotropic theory occurs for 111. We have evaluated this difference for a large number of cubic media and have obtained an estimate of its impact on epilayer critical thickness t_c for [001] oriented growth. We suggest that it tends to lower t_c for [001] oriented growth relative to that given by isotropic theory: by 15%–30% for common semiconductors and by up to a factor of 3 for metals.     

X-ray measurement of deformation and dislocation density in semiconductor strained layers

Double-crystal X-ray diffraction is commonly used to measure the misfit strain and relaxation of epitaxial semiconductor layers. In this paper, a framework is developed which links the measured parameters Δd / d and Δø to the deformation tensor of a semicoherent layer. Isotropic elasticity theory and the Frank-Bilby equation are used to derive an analytical expression for this deformation. By combining X-ray measurements of different planes, it is possible to obtain the misfit strain and details of the misfit dislocation array in a strained layer grown on a substrate of arbitrary orientation. In (001) layers, it is shown that the misfit strain and relaxation can be found from just six rocking curves, although the most accurate measurements require twelve rocking curves.     

Structural phase transitions in heteroepitaxial ferroelectric films

The changes in the structural—deformational characteristics occurring during the phase transitions in the crystal lattice of epitaxially grown thin (Ba,Sr)TiO₃ films on the (001) cleavage of MgO crystals have been studied. It is shown that microdeformations along the surface normal of the wall of a c-domain film increase with the temperature and attain maximum values in the vicinity of the phase transition. No decrease in the dimensions of the coherent-scattering regions was observed. The comparison of the deformation of the “average” lattice and microdeformations led to the assumption that the transition from the paraelectric to the ferroelectric phase is accompanied by the dislocation-induced formation of a dipole-glass-type intermediate phase at the temperatures exceeding that of the phase transition.     

X-ray diffraction study and quantitative measurements of high dislocation densities in superlattices and single crystal layers of heteroepitaxial systems with pronounced lattice mismatch

Plastic deformation in a single-crystal layer of the In_0.12Ga_0.88As/(111)InP solid solution is identified by the methods of X-ray diffractometry (XRD) and the double-crystal pseudorocking curves (DCPRC). X-ray topographs showed the generation of three intersecting systems of straight dislocations in the layer. In a one-layer ZnSe/GaAs structure and multilayer ZnSe/ZnSe_{1 − x} S_x/ZnSe/GaAs structures, the elastic and plastic strains were detected by the combined XRD-DCPRC method. The major components of the thermoelastic and plastic-deformation tensors were determined as ε_xx = ε_yy = 3.5 × 10⁻³ and ε_zz = 2.35 × 10⁻³. Using these data, the dislocation densities were determined as N _d ∼ 2.5 × 10⁸ cm⁻² and N _d ∼ 3 × 10¹⁰ cm⁻² for the 7 μm-thick ZnSe and 1 μm-thick InAs layers, respectively. In a superlattice of the Al_xGa_{1 − x} As/GaAs/⋯/GaAs-type with a large lattice parameter, the plastic deformation was detected. X-ray topography confirmed that the dislocation density in this superlattice equals ∼10⁵ cm⁻². __________ Translated from Kristallografiya, Vol. 45, No. 2, 2000, pp. 326–331. Original Russian Text Copyright ? 2000 by Kuznetsov.     

General orientational characteristics of heteroepitaxial layers of AIIBVI semiconductors on sapphire and semiconductor substrates with diamond and sphalerite structures (AIIIBV)

X-ray reflection and transmission diffractometric studies of nonisostructural heteroepitaxy showed that the spatial rotation of the crystal lattice of the grown heteroepitaxial layer with respect to the substrate lattice about the crystallographic direction common for both lattices is the most general characteristic feature of their mutual crystallographic orientation. This feature leads to the coincidence of the 〈0001〉 polar axis of the heteroepitaxial layer of the A^IIB^VI compounds with one of the 〈111〉 polar axes of the cubic substrate. The 30° and 90° rotations in the plane of heteroepitaxy and the vernier-type conjugating of the planar nets of the heteroepitaxial layer and the substrate are the particular cases of their mutual crystallographic orientations.     

Dislocation Photoconduction and Related Dislocation Memory Effects in KCl Crystals

Two types of memory phenomena are discussed, both related to dislocation photoconduction of highly pure and coloured KCl crystals, using the combination of Lyman- and F-illuminations. A very simplified explanation of the dislocation memory effects is given taking into consideration possible changes in the direction of the photocurrents. Some considerations may be of interest for the explanation of photoplastic effects.     

EPD investigation in LEC-grown silicon-doped gallium arsenide

The EPD distribution is investigated in silicon-doped LEC-grown gallium arsenide crystals, 30 ÷ 40 mm in mainbody diameter and weighing within 300 ÷ 500 grams. The silicon-doping-dependent hardening effect, previously observed in S-doped and Bridgman grown silicon-doped gallium arsenide is here confirmed. The EPD decreasing with silicon-doping increase is observed to be less pronounced than in the case of S-doped and Bridgman grown silicon-doped samples and possible reasons for this different behaviour are discussed. In any case, a large microprecipitate density together with the EPD reduction appears as a clustering of shallow-pits around dislocation pits.