SIMULATION OF THE EL2 CENTER PHYSICAL PROPERTIES IN GALLIUM ARSENIDE ACCORDING TO THE RESULTS OF THE IMPURITIES HIGH-TEMPERATURE DIFFUSION

Abstract

The nature of the annealing and diffusion effects of impurities of cadmium and selenium atoms on the change of the radiation induced by EL2 centers quantum efficiency in gallium arsenide single crystals was studied. A comparative technique of high-temperature diffusion of impurities in vacuum and arsenic atmosphere was used. According to the obtained results, modeling of structural, radiative and other physical properties of EL2 centers in single crystals of gallium arsenide was carried out. It was established that the nature and degree of change in the quantum efficiency of radiation through these centers is determined by the vacancy composition of the crystals and is determined by the probability of the formation of EL2-impurity complexes. Crystals of semiinsulating unalloyed n-type GaAs conductivity grown by the Czochralsky method with (100) orientation and resistivity ρ=7×107-2×108 Om×cm were used for the research. The concentration of EL2 centers, which are deep donors, in them was N=(1.2-1.8)×1016 cm-3. The impurity of selenium or cadmium was introduced into samples with a thickness of ~2 mm at a temperature of 900°C for 4-8 hours followed by quenching. A control annealing of samples without inclusion of impurities was also carried out. It took place in a vacuum and under excessive pressure of arsenic vapors under the same conditions as during the diffusion of selenium and cadmium. The study and modeling of the mechanisms of formation of photoluminescence spectra, selective excitation of luminescence and photoquenching of radiation through EL2 centers was carried out according to standard methods. An analysis of the obtained data was made from the point of view of modeling the structure of EL2 centers. It has been established that Ga vacancies are found in gallium-deficient crystals near AsGa antistructural defects (arsenic atoms at gallium positions). At the same time, an increase in the concentration of arsenic vacancies determines precisely their localization near AsGa antistructural defects. Therefore, the most likely solution to the question regarding the composition of the EL2 center is that the probability of formation of complexes of a certain composition is determined by the concentration of certain point defects in the crystal. A change in the concentration of point defects causes a change in the structure of the AsGa-point defect complex in favor of the dominant defect or the absence of a point defect near AsGa.