Specific features of photoconductivity in thin n-PbTe:Ga epilayers

Abstract

Photoconductivity and transient processes in thin (0.2–0.3 µm) n-PbTe:Ga epilayers were studied. The films were grown by the hot-wall technique on BaF2 〈111〉 substrates. Photoelectric properties of the samples were investigated in the temperature range from 4.2 to 300 K. A GaAs light-emitting diode and miniature incandescent lamp were used as sources of pulsed and continuous infrared radiation, respectively. The most important characteristic of the films is the very wide temperature range of photosensitivity. At an illumination power density of 10−5 to 10−4 W/cm2, the temperature at which the films become photosensitive TC is as high as 150 K, which exceeds TC for thicker films (2–3 µm) and high-resistivity single crystals of n-PbTe:Ga by 40 and 70 K, respectively. An analysis of the transient behavior of photoconductivity shows that photoexcited carriers are uniformly distributed over the volume of the thin films. A barrier for recombination of nonequilibrium charge carriers was estimated for slow relaxation processes.