中文摘要：

GaN阴极中光电子的发射分为价带电子的激发、光生载流子的输运和载流子的发射3个阶段。分析了激发阶段GaN光电阴极中电子吸收入射光产生从价带到导带的跃迁过程和输运阶段导带中的光电子从体内到表面的扩散过程及发射阶段GaN阴极表面光电子的逸出过程;推导了Cs激活过程中到达阴极表面光激发电子的逸出几率公式;比较了仅用Cs激活和共用Cs/O激活过程中到达阴极表面光激发电子逸出几率的变化情况;结果表明：GaN阴极的光电发射为直接跃迁激发,输运阶段仅遭受电子-声子散射,表面光激发电子的逸出几率取决于激活程度,引入Cs是激活的必需因素,O的引入仅可小幅度提升光电发射效率;最后利用实验证实了Cs激活的充分性。

英文摘要：

The photoemission process of negative electron affinity （NEA） GaN photocathode can be divided into three steps： photoexcitation in valence band, transport from bulk to the surface, and escape to vacuum by traversing surface harrier. Photoelectrons excited by incident light from valence band to conduction band, photoelectrons in conduction band transport from bulk to surface and photoelectrons escape to vacuum activated by only Cs or Cs/O were analyzed detailly. Then, the photoemission mechanism of NEA GaN photocathode is excited by direct transition, suffered only by electron-phonon scattering, and activation with Cs is the sufficient condition for the formation of NEA, and the photoemission efficiency only upgraded slightly by addition of O. Finally, the experiments confirmed the adequacy of Cs in the process of activation.