反射式GaN光电阴极表面势垒对量子效率衰减的影响

针对反射式GaN光电阴极长波段量子效率衰减较大, 短波段量子效率衰减较小的实验现象, 在考虑谷间散射的情况下, 利用玻尓兹曼分布和基于Airy函数的传递矩阵法, 计算了发射电子能量分布, 分析了表面势垒变化对量子效率衰减的影响, 理论与实验符合较好. 激活层有效偶极子数的减少使表面势垒宽度和高度增加, 引起长波光子激发产生的发射电子能量分布衰减较大, 短波光子激发产生的发射电子能量分布衰减较小, 这是量子效率在长波段衰减较大, 短波段衰减较小的根本原因.

Effect of surface potential barrier on quantum efficiency decay of reflection-mode GaN photocathode

Quantum efficiency decay of reflection-mode GaN photocathode is small at short wavelengths and large at long wavelengths. In light of this experimental phenomenon, the emitted electron energy distribution is calculated by using the Boltzmann distribution and transfer matrix method based on Airy function, with the intervalley scattering considered. The effect of surface potential barrier change on quantum efficiency decay is investigated. The results of theoretical calculation are in good agreement with the experiments al results. The reduction of effective dipole in activated layer leads to inereased length and height of surface barrier, which causes more decay of the emitted electron energy distribution generated by longer wavelength photons, and less decay of the emitted electron energy distribution generated by shorter wavelength photons. It is the fundamental reason of phenomenon that the decay of quantum efficiency is small at short wavelengths and large at long wavelengths.