Investigation of Photoconductivity in n-type Galium Doped PbTe

Persistent photoconductivity at low temperature in PbTe + 0.4 at. % Ga has been investigated using kinetic equations which describe the transport process on DX-like impurity centers. Measured and calculated photoconductivity as a function of illumination and temperature is presented. Experimental results are interpreted assuming the mixed valence of Ga in lead telluride and the formation of centers with negative correlation energy. Numeric values of the mathematical model constant at steady state are calculated by comparing the measured and calculated temperature dependence of the resistivity and carrier concentrations for illuminated and unilluminated n-type samples. Thus, the positions and concentrations of different impurity states are determined