A. S. Lenshin

Structure and optical properties of heterostructures based on MOCVD (AlxGa1 − xAs1 − yPy)1 − zSiz alloys

Epitaxial heterostructures produced by MOCVD on the basis of AlxGa1 − xAs ternary alloys with the composition parameter x ≈ 0.20–0.50 and doped to a high Si and P atomic content are studied. Using the high-resolution X-ray diffraction technique, scanning electron microscopy, X-ray microanalysis, Raman spectroscopy, and photoluminescence spectroscopy, it is shown that the epitaxial films grown by MOCVD are formed of five-component (AlxGa1 − xAs1 − yPy)1 − zSiz alloys.

XANES and IR spectroscopy study of the electronic structure and chemical composition of porous silicon on n- and p-type substrates

The differences in the electronic structure and composition of porous silicon samples obtained under identical conditions of electrochemical etching on the most commonly used n- and p-type substrates with different conductivities are demonstrated by X-ray absorption near-edge spectroscopy (XANES) and Fourier transform IR spectroscopy (FTIR) methods. It is shown that significantly higher oxidation and saturation with hydrogen is observed for the porous layer on n-type substrates.

Study of the morphological growth features and optical characteristics of multilayer porous silicon samples grown on n -type substrates with an epitaxially deposited p + -layer

This study is concerned with the growth features of multilayer porous silicon with layers of different porosity, obtained by electrochemical etching on an n-type single-crystal silicon (111) wafer with a p+-layer epitaxially deposited onto the surface. The possibility of obtaining a multilayer system of ordered pores of various sizes within a single technological cycle is demonstrated. The differences in the optical characteristics of separate layers of the grown structure are shown.

Structural and spectral features of MOCVD AlxGayIn1 − x − yAszP1 − z/GaAs (100) alloys

The study is concerned with MOCVD epitaxial heterostructures grown on the basis of AlxGayIn1 − x − yAszP1 − z quinary alloys in the region of alloy compositions isoperiodic to GaAs. By the X-ray diffraction technique and atomic force microscopy, it is shown that, on the surface of the heterostructures, there are nanometric objects capable of lining up along a certain direction. From calculations of the crystal lattice parameters with consideration for internal strains, it can be inferred that the new compound is a phase based on the AlxGayIn1 − x − yAszP1 − z alloy.

Investigations of nanodimensional Al2O3 films deposited by ion-plasma sputtering onto porous silicon

The purpose of this study is the deposition of nanodimensional Al2O3 films on the surface of nanoporous silicon and also fundamental investigations of the structural, optical, and morphological properties of these materials. Analyzing the results obtained here, it is possible to state that ultrathin nanostructured Al2O3 films can be obtained in the form of threads oriented in one direction and located at a distance of 300–500 nm from each other using ion-plasma sputtering on a layer of porous silicon. Such a mechanism of aluminum-oxide growth is conditioned by the crystallographic orientation of the initial single-crystalline silicon wafer used to fabricate the porous layer. The results of optical spectroscopy show that the Al2O3/por-Si/Si(111) heterophase structure perfectly transmits electromagnetic radiation in the range of 190–900 nm. The maximum in the dispersion of the refractive index obtained for the Al2O3 film grown on por-Si coincides with the optical-absorption edge for aluminum oxide and is located in the region of ~5.60 eV. This fact is confirmed by the results of calculations of the optical-absorption spectrum of the Al2O3/por-Si/Si(lll) heterophase structure. The Al2O3 films formed on the heterophase-structure surface in the form of nanodimensional structured threads can serve as channels of optical conduction and can be rather efficiently introduced into conventional technologies, which are of great importance in microelectronics and optoelectronics.

Study of the processes of degradation of the optical properties of mesoporous and macroporous silicon upon exposure to simulated solar radiation

The effect of solar radiation on the surface composition of mesoporous and macroporous silicon is studied by infrared spectroscopy, Raman spectroscopy, and photoluminescence measurements in order to analyze the possibility of using these materials as a material for solar-power engineering. The studies are conducted in the laboratory environment, with the use of a solar-radiation simulator operating under conditions close to the working conditions of standard silicon solar cells. The studies show that, in general, the materials meet the requirements of solar-power engineering, if it is possible to preclude harmful effects associated with the presence of heat-sensitive and photosensitive bonds at the nanomaterial surface by standard processing methods.

Specific features of the sol-gel formation and optical properties of 3d metal/porous silicon composites

The composition and optical properties of composite materials based on porous silicon with iron, cobalt, and nickel deposited by the sol-gel technique are studied. It is shown that the deposition of metal-oxide films onto the surface of porous silicon enables stabilization of the photoluminescence and an increase in its intensity, as well as the storage of hydrogen in the porous layer.

Structural and optical properties of heavily doped AlxGa1 − xAs1 − yPy:Mg alloys produced by metal-organic chemical vapor deposition

The high-resolution X-ray diffraction technique, Raman spectroscopy, and photoluminescence spectroscopy are used to study the structural, optical, and electron energy properties of epitaxial AlxGa1 − xAs1 − yPy:Mg alloy films grown by metal-organic chemical vapor deposition (MOCVD). It is shown that the introduction of a Mg impurity into the quaternary alloy provides high charge-carrier concentrations. A decrease in the growth temperature yields a decrease in the charge-carrier concentration in films doped with magnesium at a small gas-carrier flux of the acceptor impurity, whereas an increase in the flux results in an increase in the acceptor-impurity concentration, which is reflected in the character of the photoluminescence spectra.

Experimental studies of the effects of atomic ordering in epitaxial Ga x In1–x P alloys on their structural and morphological properties

The properties of epitaxial GaxIn1–xP alloys with an ordered arrangement of atoms in the crystal lattice are studied by a number of structural and microscopic methods. The alloys are grown by metal-organic chemical vapor deposition onto single-crystal GaAs(100) substrates. It is shown that, under conditions for the coherent growth of an ordered GaxIn1–xP alloy on a GaAs(100) substrate, atomic ordering results in radical modifications of the structural properties of the semiconductor compared to the properties of disordered alloys. Among these modifications are a change in the crystal-lattice parameter and, as a consequence, lowering of the crystal symmetry and the formation of two different types of surface nanorelief. With consideration for elastic strains, the parameters of GaxIn1–xP alloys with ordering as functions of the order parameter are calculated for the first time. It is shown that all experimental data are in good agreement with the developed theoretical concepts.

Al x Ga 1 − x As/GaAs(100) hetermostructures with anomalously high carrier mobility

Structural and spectroscopic methods are used to study the epitaxial layers of n-type AlxGa1 − xAs solid solutions produced by the metal-organic chemical vapor deposition method. It is shown that, when AlxGa1 − xAs solid solutions are doped with carbon to a level of (1.2–6.7) × 1017 cm−3, the electron mobility is anomalously high for the given impurity concentration and twice exceeds the calculated value. It is assumed that the ordered arrangement of carbon in the metal sublattice of the solid solution leads to a change in the average distance between impurity ions, i.e., to an increase in the mean free path of the carriers and, consequently, in the carrier mobility. The observed effect has immediate practical importance in the search for various technological ways of increasing the operating speed of functional elements of modern optoelectronic devices. The effect of the anomalously high carrier mobility in the epitaxial layer of a heteropair opens up new opportunities for the development of new structures on the basis of AlxGa1 − xAs compounds.