Dark-current of field-assisted GaAs semiconductor photocathodes

The dark-current of GaAs field-assisted photocathodes with red and near infrared response is larger than that of common GaAs photocathodes. The major source of dark- current of the photocathodes is impact ionization of hot holes in high field deple- tion region. In this paper, a model and creating mechanism of impact ionization in the photocathodes is described in detail, and a specific expression of the dark-curren of the photocathodes at different operation conditions can be predicted once the appro- priate parameters have been determined. It may be helpful to design a field-assisted photocathode and choose an optimum operation condition.