透射式GaN光电阴极在正面光照和背面光照下的量子效率特性研究

Quantum Efficiencies of Transmission-Mode GaN Photocathode under Front and Back Illumination

研究了透射式GaN光电阴极在正面光照和背面光照两种工作模式下的光电发射特性差异及影响因素,并推导了这两种工作模式下的量子效率理论公式,利用所推导的公式对实验获得的GaN光电阴极量子效率曲线进行了分析。研究结果表明,两种工作模式下光电子的表面逸出几率与光子能量具有不同的依赖关系,背面光照下,光电子将以一个一致的表面逸出几率从表面发射出去,并且短波响应会受到缓冲层及界面特性的影响,总体光电发射效率依赖于阴极表面势垒所决定的平均电子逸出几率。利用所推导的量子效率公式对实验曲线进行拟合,可实现多个阴极参量的评估,这为透射式GaN阴极材料与制备工艺水平的分析提供了重要依据。

The photoemission characteristics and the influencing factors of the transmission-mode GaN photocathode under front and back illumination were studied.The quantum efficiencies under front and back illumination were theoretically formulated and measured.The results show that the illumination mode strongly affects the emission probability and energy of the photoelectrons.Under back illumination,the photoelectrons have a fairly uniform emission probability,and the buffer layers and the interfacial property limit its shortwave response.The total photoemission efficiency depends on the average emission probability,strongly affected by the surface barrier.In addition,the key parameters of the transmission-mode photocathode,fabricated with different materials and by different techniques,can be evaluated by fitting the experimental data with the newly-developed,quantum efficiency formula.