Decay characteristics and mechanism of GaN UV photocathode

Summary form only given. Recent progress in Gallium Nitride (GaN, AlGaN, InGaN) photocathodes show great promise for future ultraviolet (UV) detector applications. Stability has been one main performance parameters for photocathode. The photoemission decay characteristics of GaN photocathode after the end of activation in ultra-high vacuum system was investigated using photocurrent and spectral response on-line monitoring measurement. It was found that under low-level light irradiation, the photocurrent of GaN photocathode decays at a very slow rate during a long period, and then began to decay suddenly at a faster speed. The spectral response curve reflects the attenuation of long-wave response is greater than short-wave one. GaN photoemission performance can be restored by Cs replenishment, which indicates that Cs desorption is the main reason for GaN cathode degradation in vacuum system. The influences of Cs desorption on GaN cathode surface barrier and photoelectron surface escape probability were analyzed based on surface model of cesium-oxygen activated GaN cathode, and the reasons for observed GaN cathode decay behaviors were explained.