Theoretical calculation of dark current for a field-assisted semiconductor photocathode

The dark-current source of a semiconductor field-assisted photocathode has been theoretically analysed and calculated. Under a given temperature of operation, a principal source of dark-current emission from the cathode is the impact ionisation component of hot holes in the Schottky barrier range. A specific expression for the multiplication factor of the impact ionisation is obtained. According to the theoretical calculation, the emission intensity of dependence of dark-current on the applied bias, doping concentration and operating temperature has been predicted. It may be helpful to design a field-assisted photocathode and choose an optimum operation condition.