High current density GaN∕CsBr heterojunction photocathode with improved photoyield

Abstract

A four fold improvement in photoyield has been observed in GaN films coated with CsBr films (CsBr∕GaN) relative to CsBr∕Cr photocathodes reported in previous studies. A model is presented involving photoemission from intraband states in the CsBr film and direct electron injection through the CsBr film from the GaN substrate. The lifetime of the films at high current density >90A∕cm2 is limited by the temperature rise in the GaN films caused by the high photon absorption at 257nm. The lifetime can be improved by utilizing a cooled substrate or a high thermal conductivity substrate under the GaN films.