A DFT study on NEA GaN photocathode with an ultrathin n-type Si-doped GaN cap layer

Abstract

Due to the drawbacks of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, a new-type NEA GaN photocathodes with heterojunction surface dispense with Cs activation are proposed. This structure can be obtained through the coverage of an ultrathin n-type Si-doped GaN cap layer on the p-type Mg-doped GaN emission layer. The influences of the cap layer on the photocathode are calculated using DFT. This study indicates that the n-type cap layer can promote the photoemission characteristics of GaN photocathode and demonstrates the probability of the preparation of a NEA GaN photocathode with an n-type cap layer.