Laser Saturation of Photoconductivity and Determination of Imperfection Parameters in Sensitive Photoconductors

Saturation of photoconductivity is a valuable technique in the determination of imperfection parameters in sensitive photoconductors. Measurements of saturation of photoconductivity using high-intensity excitation from a ruby laser have been made on a single crystal of Cd(S0.5—Se0.5), selected for its band gap to give appreciable but approximately homogeneous excitation, as a function of temperature between 80° and 400°K. The density of sensitizing centers can be obtained directly from such measurements, together with information about the densities and depths of traps that influence the saturation process. For the crystal investigated, the density of sensitizing centers is 7×1015 cm−3. Knowledge of the density of sensitizing centers permits a direct determination of both photon absorption and electron-capture cross sections for these centers. Values obtained in this way are in good agreement with values independently determined.