Study of Negative Electron Affinity Property for Varied Doping GaN Photocathode

Negative electron affinity (NEA) property means that the vacuum level is lower than the conduction band minimum in the bulk. For GaN photocathode, the effective electron affinity of the material is smaller than zero. According to Spicer "3-step model", the photoemission mechanism for varied GaN photocathode was studied. For the varied doping GaN photocathode, the photoelectrons can be transported to the surface by diffusing and drifting in the directional inside electric field, and the higher photoemission performance can be obtained. By covering with low escape power materials such as Cs or O on an atomically clean surface, Negative electron affinity property can be achieved for the varied doping GaN photocathode. Using the activation and evaluation system for NEA photocathode, the varied doping GaN photocathode was activated with Cs and O, and the photocurrent curve for varied doping GaN photocathode was gotten.