Low temperature contact system intended for optoelectronic devices based on the AlGaAs/GaAs heterostructure was investigated. The technological routine for Pd/Ge/Au contact multilayer stack with annealing temperatures reduced to 170-190 degrees C was identified. This identification makes it possible to produce reproducibly the terminals with low resistance (specific resistivity of 1-3 & sdot;10-6 52 center dot cm2) for the n-GaAs layer in order to decrease the temperature impact on both the heterostructure and the metal layers of the integrated reflector, as well as to avoid their degradation. A peak efficiency of 60 % (180 W/cm2) was recorded for the AlGaAs/GaAs photovoltaic converters of laser radiation (800-850 nm) with ohmic contact Pd/Ge/Au. With the increased laser power density up to 500 W/cm2, the efficiency was constantly maintained at a level above 55 %.

The investigations of Pd/Ge/Au contact system forming regimes influence on the specific contact resistivity to n-type conductivity GaAs layer were carried out. The method of samples surface treatment before the layers evaporation and thermal annealing regimes in H 2 , N 2 and Ar atmosphere influence on contact system parameters was investigated. The specific contact resistivity value (2-3)· 10 -6 Ohm· cm 2 at the reduced annealing temperature 190 o C was archived.. Keywords: Pd/Ge/Au, n-GaAs, surface treatment, thermal annealing

Development of lift-off technique of AlGaAs/GaAs- heterostructures, grown by the Metalorganic vapour-phase epitaxy, to GaAs carrier-substrate using silver-containing paste or Au-In compound has been carried out. Forming process of frontal ohmic contact to GaAs n-type conductivity based on contact systems Au(Ge)/Ni/Au and Pd/Ge/Au with specific contact resistance (2-5)·10 -6 Ω·cm 2 has been investigated. Analyzed was the influence of heterostructure lift-off technique and forming process of frontal ohmic contact on the IR light-emitting diodes parameters: minimum light-emitting diodes (1 mm 2 square) series resistance was 0.16 Ω. Optical power 270 mW at current 1.5 A has been achieved. Keywords: AlGaAs/GaAs- heterostructure, light-emitting diode, transfer to carrier-substrate, Au--In- compound, ohmic contacts.

Development of lift-off technique of AlGaAs/GaAs heterostructures, grown by the MOCVD technique, to GaAs carrier-substrate using silver-containing paste or Au-In compound has been carried out. Forming process of frontal ohmic contact to GaAs n-type conductivity based on contact systems Au(Ge)/Ni/Au and Pd/Ge/Au with specific contact resistivity 2-5·10-6 Ом·см2 has been investigated. Analyzed was the influence of heterostructure lift-off technique and forming process of frontal ohmic contact on the IR light-emitting diodes parameters: minimum light-emitting diodes (1mm2 square) series resistance was 0.16 Ohm. Optical power 270 mW at current 1.5A has been achieved.

The paper presents the results of a study of factors affecting the thickness of transition (interface) layers in stressed InAs/GaSb superlattices during growth by MOCVD method. It is shown that the thicknesses of the interface layers between InAs and GaSb are practically independent of the growth temperature. The thickness of the interface layers is influenced by the direction of switching the layer growth. The smallest thickness of 1.2-1.4 nm of the interface layer InAs/GaSb was obtained for the direction of growth switching from GaSb to InAs. Keywords: MOCVD, stressed superlattice, InAs/GaSb, interface layer, transmission electron microscopy.

The investigations of Pd/Ge/Au contact system forming regimes influence on the specific contact resistivity to n-type conductivity GaAs layer were carried out. The method of samples surface treatment before the layers evaporation and thermal annealing regimes in H2, N2 and Ar atmosphere influence on contact system parameters was investigated. The specific contact resistivity value 2-3•10-6 Ohm•cm2 at the reduced annealing temperature 190 C was archived.

The zinc diffusion process into InP through a thin InGaAs layer using diethylzinc (DEZn) as a p-dopant source was investigated. The distribution profiles of electrically active dopant in InGaAs/InP heterostructures were obtained by electrochemical capacitance-voltage profiling technique. The influence of temperature and pressure in the reactor, DEZn flow rate and process time on the concentration of holes and the diffusion depth was investigated. The process of zinc diffusion strongly depends on the zinc concentration at the surface, however, the maximum concentration of holes and the depth of zinc diffusion into the InP layer might be chosen independently in a certain range of values.

The characterization of Si-doped GaSb epitaxial layers, grown by metal-organic vapor-phase epitaxy at a constant SiH4 flow with a TMSb/TEGa ratio ranging from 1 to 50, is presented. X-ray diffraction rocking curves, photoluminescence spectra, Raman scattering spectra, resistivity, concentration of free carriers, and their mobility in GaSb:Si layers are analyzed.

The paper presents the results of a study of factors affecting the thickness of transition (interface) layers in stressed InAs/GaSb superlattices during growth by MOCVD method. It is shown that the thicknesses of the interface layers between InAs and GaSb are practically independent of the growth temperature. The thickness of the interface layers is influenced by the direction of switching the layer growth. The smallest thickness of 1.2-1.4 nm of the interface layer InAs/GaSb was obtained for the direction of growth switching from GaSb to InAs.

Raman spectra of GaxIn1-xAsySb1- y alloy with x = 79-95 % and y = 5-25 % have been studied. Strong corre-lation of main LO1 and LO2 mode splitting with arsenic concentration is found. Model of Raman bands origin based on phase separation observed by structural studies is suggested. Ways of practical implementation of Raman spectroscopy for alloy composition determination are presented.

Charachterization of Si-doped GaSb epitaxial layers grown by metal organic vapor phase epitaxy is presented. Samples are grown at constant SiH4 flow with a TMSb/TEGa ratio ranged from 1 to 50. X-ray diffraction, Raman scattering, photoluminescence, resistivity, free carrier concentration and their mobility are studied.

The results of studying the conditions for obtaining an atomically smooth surface of GaSb substrates are presented for the first time. It has been shown experimentally that it is possible to improve the surface quality of the samples by changing the annealing conditions. The smallest roughness of 1.3 nm was obtained for an annealing time of 16 min at a temperature of 650°C in a flow of trimethylantimony and H 2 .

In the study of doped anisotypic heterostructures with layers of Ga(1-x)In(x)P(1-y)As(y) grown on InP substrates with a buffer layer of InP by MOC-hydride epitaxy, the presence of transition regions was detected in the Ga(1-x)In(x)P(1-y)As(y) layer on the substrate side for individual samples, across which the arsenic content (y) increased from the interface with the InP layer to the surface of the structure by the amount of (Δy) up to 0.15, and the content of elements of the third group (x) remained constant.

For the first time, the results of a study of the conditions for obtaining an atomically smooth surface of GaSb substrates are presented. It is shown experimentally that it is possible to improve the surface quality of the samples by changing the annealing conditions. The lowest obtained roughness of 1.27 nm was obtained at an annealing time of 16 minutes at a temperature of 650°C in the flow of TMSb and H2.

When studying doped anisotypic heterostructures with Ga1 – xInxAsyP1 – y layers grown on InP substrates with an InP buffer layer by metal organic chemical vapor deposition, the presence of transition regions is revealed in the Ga1 – xInxAsyP1 – y layer from the side of the substrate in some of the samples, along which the arsenic content (y) increases from the interface with the InP layer to the surface of the structure by a Δy value of up to 0.15, while the content of elements of the third group (x) remains constant.

In this work, we studied the surface quality dependence of GaSb and InP substrates prepared by various methods of pre-epitaxial preparation, specifically, etching, annealing, and growing a buffer layer. Our main goal was to obtain the most efficient method of pre-epitaxial treatment, which allows preparing substrates with the best surface quality. The experimental results were evaluated by the parameter of the average roughness of the substrate. As a result a combination of the methods of pre-epithelial preparation of GaSb and InP substrates was selected, which made it possible to obtain a root-mean-square surface roughness about 0.6–0.8nm.

Abstract It is necessary to minimize the resistance of electrical contacts to reduce heat losses in photovoltaic converters of laser radiation. The paper describes ways to reduce the resistance of electrical contacts for p-InP by choosing the composition of the subcontact layer based on p-InGaAs. For this purpose, layers of p-InGaAs with different compositions and bandgaps were grown by the MOCVD method. AgMn/Ni/Au contact metallization was deposited on samples to compare the characteristics of electrical contacts. The minimum specific contact resistance was 7• 10−5 Ω-cm2 for the layer with Eg = 0.51 eV.

Luminescence properties of epilayers of Ga 1 – x In x As y P 1 – y (GaInAsP) solid solutions with graded content of Group V elements (Δ y up to 0.08 over a total thickness of about 1 μm) were studied at 77 and 300 K. The photoluminescence (PL) spectra of GaInAsP epilayers with large Δ y values were broadened. The GaInAsP epilayers of low crystalline perfection exhibited either no PL emission or showed PL spectra characteristic of transitions involving impurity energy levels.

The electroluminescent characteristics of a type-II n-GaSb/n-InAs/p-GaSb heterostructure with a single deep quantum well grown by metalorganic vapor-phase epitaxy are investigated. The energy-band diagram of the structure and the positions of the electron and heavy-hole energy levels are calculated. The analysis of the current–voltage characteristics demonstrates that the dark current in the structure under study flows via the tunneling mechanism. Intense electroluminescence characterized by a weak temperature dependence was observed in the spectral range of 3–4 μm at T = 77 and 300 K. The main electroluminescence band (hν = 0.40 eV at 77 K) corresponds to direct radiative transitions between electrons from level E1 in the InAs quantum well and heavy holes from the continuum at the n-GaSb/n-InAs heterointerface. A low-intensity electroluminescence band at hν = 0.27 eV (T = 77 K) originates from indirect (tunneling) transitions from the first electron level in the quantum well to the second level of heavy holes localized in the valence-band “notch” at the n-InAs/p-GaSb heterointerface.

The photoluminescent properties at 77 and 300 K are investigated for Ga1 xInxAsyP1 y epilayers with V-group elements content gradient Δy up to 0.08 across whole thickness (about 1 µm). Ga1 xInxAsyP1 y layers with high Δy values have widened photoluminescence spectra. For GaInAsP layers of low crystaline perfection, photoluminescence was either absent or manifested itself as it is typical for transitions involving impurity levels.