Fast photodischarge of selenium electrophotographic layers

Fast photodischarge (10(-3)-10(-7) sec) of electrophotographic selenium layers due to strongly absorbed light pulses (10(-7) sec) has been investigated by means of differential and integral methods. The results provide valuable information on the conditions of carrier drift and trapping during discharge. Se layers are found to possess high density of hole and shallow electron traps concentrated predominately at the surface of a layer. The discharge lag up to 10(-3) sec is caused by thermal release from the traps filled during exposure and carrier drift. Electron and hole drift mobilities in amorphous selenium layers, measured directly, do not differ from other similar data. Carrier mobility in As(2)Se(3) layers is measured; the electrons are found to be practically immobile, while hole mobility is equal (1-5) x 10(-5) cm(2)/V sec. Space charge influences the photodischarge kinetics and transit time. The theoretical dependence on geometrical distribution of space charge in a layer is found to be in satisfactory agreement with the experimental data.