Wavelength dependence of persistent photoconductivity in indium-doped Pb1-xSnxTe

Abstract

The authors have measured the wavelength dependence of persistent photoconductivity in films of indium-doped Pb0.75Sn0.25Te using a cryogenically cooled spectrometer to avoid saturation of the photoresponse from the room-temperature thermal background. Using only the 300 K blackbody radiation incident on the entrance slit of the spectrometer, they observed a 2% drop in the sample resistivity when the grating was rotated to pass a 0.1 mu m band width centred at lambda =14 mu m. At longer wavelengths the resistivity drop increased, reaching 30% at 50 mu m. They interpret these results in terms of a configuration coordinate model of the lattice relaxation around the indium impurity site. They estimate the quantum efficiency of this material to be about 0.3% before the photoresponse saturates. The large photoconductive gain ( approximately 107) which results from the long persistence may be useful in detectors for some slow imaging applications.