Stril'chuk O. Study of defect states in semi-insulating undoped gallium arsenide

Radiative recombination of excess change carriers on defect states induced by residual impurities and lattice defects in specially undoped semi-insulating GaAs. The aim - to reveal the interaction of defect states one with the another and make clear the effect of thermal treatment on them by means of a study of radiative recombination of excess charge carriers in GaAs. The method - the investigation of photoluminescence spectra of crystals with different content of residual impurities in a wide temperature range and at different excitation levels. It is shown that in semi-insulating GaAs essential interaction of defect states occurs, i.e. the impurities interact with each other and they interact with lattice defects and with free excitons. The role of carbon impurity in gallium divacancies formation is determined. It is shown that the luminescence band at h(m =1.5133 eV is caused by radiative recombination in the exciton-impurity complex consisting of ionized shallow donor and exciton. The effect of h eat treatment at 900 C, 20-90 min on the impurity content in semi-insulating GaAs crystals, in particular, the increase of the acceptor content and non- monotonous change of the donor concentration, was observed. A contactless express method for the quantitative determination of carbon, zinc and silicon content in semi-insulating GaAs is proposed.