PHOTOCONDUCTIVITY SPECTRA AND THE PROBLEM OF IMPURITY STATES IN PBTE(GA)

The photoconductivity spectra near the intrinsic absorption edge were investigated for PbTe(Ga) single crystals and films in the temperature range 77-100 K. In the case of single crystals a sharp peak in the ph otoconductivity is observed in the energy range similar to 20 meV belo w the band gap. The relative amplitude of the peak is determined by th e method employed to synthesize the single crystals and is virtually i ndependent of the temperature. In the case of the PbTe(Ga) films the s tructure of the absorption edge is described well by the standard rela tion for undoped PbTe, and the amplitude of the additional peak is sma ll. The data are interpreted on the basis of a model of electronic tra nsitions which presupposes the existence of one- and two-electron stat es of the Ga impurity in PbTe. (C) 1995 American Institute of Physics.