OPTICAL AND PIEZOSPECTROSCOPIC PROPERTIES AND THE STRUCTURE OF GALLIUM-VACANCY-SILICON COMPLEXES IN N-TYPE GAAS - COMPARISON WITH GALLIUM-VACANCY-TIN COMPLEXES

This paper discusses the photoluminescence of VGaSiGa complexes in n-t ype GaAs at low temperatures. The excitation spectrum and the luminesc ence polarization spectrum with excitation by polarized light from the impurity absorption band have been measured, along with the effect of uniaxial pressure on the luminescence excited by light from the intri nsic absorption band of GaAs. A two-step alignment of distortions of t he complexes with pressure along the [111] or [110] axis and the chang es associated with them in the rate at which the luminescence band shi fts with pressure have been detected. The structure and properties of complexes of this type are qualitatively explained in a model which as sumes that, in the radiative state, the influence of the donor on the vacancy orbitals is small compared with the interaction of the hole lo calized at these orbitals with the incompletely symmetrical F-2 vibrat ions of the V(Ga)4As quasi-molecule. An analysis of the data shows tha t the difference in the piezospectroscopic properties of VGaSiGa and V GaSnGa is caused by a certain increase in the splitting of the ta vaca ncy states by the donor in VGaSiGa by comparison with VGaSnGa. The dif ferences in the piezospectroscopic behavior of these complexes, on one hand, and of the VGaTeAs complex, on the other, are mainly determined by the difference in the positions of the donors and not directly by their chemical nature. (C) 1996 American Institute of Physics.