Decay Characteristic of Gallium Nitride Photocathode in a High Vacuum System

Abstract

The decay characteristics of the originally-activated GaN photocathode are explored by testing the change of quantum efficiency (QE).The QE after degradation for 9 hours can still keep more than 42% of the original value, and after reactivated with cesium, the QEs are almost recovered. The restorations of both the band bending and the ideal Cs/O ratio on the surface, along with the double dipole model are proposed to explain the QE variation of the GaN photocathode. Further exploration should include the roles played by the achievement of the maximum band bending of the GaN surface when deposited with Cs and its relationship with the surface Mg doping concentration.