The effects of the porous buffer layer and doping with dysprosium on internal stresses in the GaInP:Dy/por-GaAs/GaAs(100) heterostructures

Semiconductors - In structures with a porous buffer layer, residual internal stresses caused by a mismatch between the crystal-lattice parameters of the epitaxial GaInP alloy and the GaAs substrate...     

Optical generation of free charge carriers in thin films of tin oxide

The methods of infrared absorption spectroscopy and Raman spectroscopy are used to study nanocrystalline SnO _x films (1 ≤ x ≤ 2) prepared by thermal oxidation of metallic tin layers. A monotonic decrease in the transmittance of films in the infrared region has been observed as a result of exposure of the films to light with the wavelength of 380 nm at room temperature. The effect is at a maximum for the samples with x ≈ 2 and is observed for ∼10 min after switching off of illumination. The mentioned variations in optical properties, similarly to those observed in the case of heating of the samples in the dark, are accounted for by an increase in the concentration of free charge carriers (electrons) in nanocrystals of tin dioxide. The data of infrared spectroscopy and the Drude model are used to calculate the concentrations of photogenerated charge carriers (∼10¹⁹ cm⁻³); variations in these concentrations in the course of illumination and after switching off of illumination are determined. Mechanisms of observed photogeneration of charge carriers in SnO _x films and possible applications of this effect to gas sensors are discussed.     

The substructure and luminescence of low-temperature AlGaAs/GaAs(100) heterostructures

The substructure and luminescence of low-temperature epitaxial AlGaAs alloys are studied by Raman spectroscopy and photoluminescence spectroscopy. It is shown that the experimental data obtained in the study are consistent with the results of the previous structural and optical study. The assumption that, at high concentrations of carbon acceptors, the acceptor atoms concentrate at lattice defects of the AlGaAs crystal alloys to form carbon nanocrystals is confirmed.