PIEZOSPECTROSCOPIC BEHAVIOR AND STRUCTURE OF THE 0.95-EV PHOTOLUMINESCENCE CENTERS IN GAAS DOPED WITH TE OR SN

The effect of uniaxial pressures of up to similar to 10 kbar on the ph otoluminescence band at similar to 0.95 eV in GaAs has been studied. T he dependence of the emitted light polarization on pressure indicates reorientation and alignment of centre distortions at certain pressure directions and magnitudes. These dependences for GaAs:Te and GaAs:Sn d iffer qualitatively but correlate with similar dependences observed fo r the photoluminescence band at similar to 1.2 eV in the same crystals , which are due to VGaTeAs and VGaSnGa complexes, respectively. These facts, together with those from the literature, suggest that photolumi nescence at similar to 0.95 eV is caused by VAsVGaTeAs complexes in Ga As:Te and by VAsVGaSnGa complexes in GaAs:Sn. Models describing the sp atial structure of these complexes are proposed which assume that, in the initial (undistorted) state, V-Ga, Te-As and Sn-Ga are respectivel y located at sites of the As or Ga sublattice adjacent to V-Ga It is s upposed that all the components of the VAsVGaSnGa complex lie in a pla ne of the (112) type. Moreover, in the region of the complex there exi sts an additional distortion directed along an axis of the (111) type which does not coincide with any axis connecting the components of the complex. For VAsVGaTeAs this distortion can reorientate itself withou t pressure at low temperatures. For VAs VGaSnGa this reorientation may occur in groups of complexes with a certain orientation with respect to the pressure direction when a pressure of 4-5 kbar is applied along a (111)- or (110)-type axis.