In the design of photocathode, the internal electric field could be formed due to the graded Al compositional ${\mathrm{\text{Al}}}_x{\mathrm{\text{Ga}}}_{1-x}\mathrm{\text{As/GaAs}}$ nanostructure, which can improve the top surface emission probability of carriers. In this paper, ${\mathrm{\text{Al}}}_x{\mathrm{\text{Ga}}}_{1-x}\mathrm{\text{As/GaAs}}$ nanostructure array photocathode composed of two sub-layers is presented. Based on the finite element method, the influence of graded geometrical parameters on their optoelectronic characteristics is investigated. The results show that when the thickness of the sublayer is equal, the difference of the Al composition between the two sublayers of nanostructure is larger, the sub-layers are less, and the quantum efficiency is higher. The light capture ability of the photocathode can be enhanced by increasing the thickness and the array spacing of the first sublayer. Compared with the hexagonal cross-section structure, the light trapping effect and spectral response of the circular cross-section structure are better.

在光电阴极的设计中，由于Al组分的渐变，可以形成内部电场。 ${\mathrm{\text{铝}}}_X{\mathrm{\text{嘎}}}_{1-X}\mathrm{\text{砷化镓/砷化镓}}$纳米结构，可以提高载流子的顶面发射概率。在本文中，${\mathrm{\text{铝}}}_X{\mathrm{\text{嘎}}}_{1-X}\mathrm{\text{砷化镓/砷化镓}}$提出了由两个子层组成的纳米结构阵列光电阴极。基于有限元方法，研究了渐变几何参数对其光电特性的影响。结果表明，当亚层厚度相同时，两个纳米结构亚层之间的Al成分差异较大，亚层较少，量子效率更高。通过增加第一亚层的厚度和阵列间距，可以增强光电阴极的光捕获能力。与六边形截面结构相比，圆形截面结构的光捕获效果和光谱响应更好。