Temperature dependence of the photocurrent excited above the fundamental absorption edge of PbW04

Photocurrent of lead tungstate (PbWO4) single crystals has been studied in the temperature range from 4 K to 270 K. The excitation spectrum of the photocurrent characterized by a prominent peak at 4.1 eV and a rise above 4.5 eV was obtained at 270 K. Below 150 K, the photocurrents excited at 4.15 eV and 4.7 eV show analogous temperature dependence with each others. However, the photocurrent excited at 4.15 eV exhibits thermal activation type temperature dependence above 150 K. We find that the photocurrent showing thermal activation is induced efficiently by the excitation at 4.12 eV, but by neither the exci-tonic transition nor the band-to-band transition. The temperature dependence of the photocurrent is discussed in terms of temperature dependence of the mobility and the carrier density.