Search

This work is devoted to the study of the luminescence inhomogeneity nature of bulk (GaxAl1–x)2O3 samples grown by the Czochralski method. In the study of sample cleavages by the local cathodoluminescence method, regions with different luminescence were observed. To determine the cathodoluminescence contrast nature, we studied the uniformity of the aluminum distribution, the surface topography, and compared the luminescence spectra and the kinetics of emission bands for different regions of the sample. Also, to determine the luminescence bands nature, the crystal was annealed in air at 1000°C. This made it possible to observe the change in luminescence for the same region of the sample. Based on the studies performed, it was concluded that inhomogeneous luminescence is associated with the distribution of point defects. Upon annealing in air, the transformation of nonradiative recombination centers into luminescent centers was observed. [ABSTRACT FROM AUTHOR]

The aluminum distribution in the surface layer of an (AlxGa1 –x)2O3 crystal grown on a sapphire seed by the Czochralski method has been studied using X-ray fluorescence and X-ray diffraction mapping and scanning electron microscopy. It is shown that the aluminum distribution correlates with a change in the physical broadening of the diffraction maxima of the (h00) plane system of the crystal and is related to a distance from the seeding zone. [ABSTRACT FROM AUTHOR]

A new mechanism of nonradiative recombination of nonequilibrium carriers in semiconductor quantum wells is suggested and discussed. For a studied Auger recombination process the energy of localized electron-hole pair is transferred to barrier carriers due to Coulomb interaction. The analysis of the rate and the coefficient of this process is carried out. It is shown, that there exists two processes of thresholdless and quasithreshold types, and thresholdless one is dominant. The coefficient of studied process is a non-monotonous function of quantum well width having maximum in region of narrow quantum wells. Comparison of this process with CHCC process shows that these two processes of nonradiative recombination are competing in narrow quantum wells, but prevail at different quantum well widths. [ABSTRACT FROM AUTHOR]

The luminescence properties of undoped epitaxial layers of gallium nitride grown on silicon carbide substrates by gas-phase epitaxy in a chloride system have been investigated. An edge band (361 nm, 96 K) and defect bands (380, 430, 560 nm, 96 K) were recorded in the photo- and cathodoluminescence spectra. It was observed that the parameters of the edge and defect luminescence bands for the GaN layers studied do not depend on the crystalline perfection of the substrate, but rather they are determined by the growth conditions, specifically, the position of the sample in the reactor. It is shown that there exists a characteristic symmetry of the distribution of the luminescence properties of a layer along the surface of the samples relative to the direction of the gas flow in the reactor. A correlation is established between the parameters of the edge and blue luminescence bands and the density of the electrically-active impurity in the epitaxial layer. [ABSTRACT FROM AUTHOR]

This work is devoted to the study of the luminescence inhomogeneity nature of bulk (GaxAl1–x)2O3 samples grown by the Czochralski method. In the study of sample cleavages by the local cathodoluminescence method, regions with different luminescence were observed. To determine the cathodoluminescence contrast nature, we studied the uniformity of the aluminum distribution, the surface topography, and compared the luminescence spectra and the kinetics of emission bands for different regions of the sample. Also, to determine the luminescence bands nature, the crystal was annealed in air at 1000°C. This made it possible to observe the change in luminescence for the same region of the sample. Based on the studies performed, it was concluded that inhomogeneous luminescence is associated with the distribution of point defects. Upon annealing in air, the transformation of nonradiative recombination centers into luminescent centers was observed. [ABSTRACT FROM AUTHOR]