InP/InGaAs转移电子光阴极吸收层厚度设计与计算

采用基于密度泛函理论的第一性原理平面波赝势法计算了InP/InGaAs转移电子光阴极吸收层材料的电学结构和光学性质,交换关联能采用杂化泛函HSE06来描述。首先对闪锌矿结构GaAs材料能带图进行计算验证,接着建立标准InGaAs材料体结构模型,并对模型进行了动力学的自洽优化,在优化后的基础上进行了非自洽的计算,得到标准InGaAs材料的复介电函数,然后根据Kramers-Kronig关系推出标准InGaAs材料光吸收系数。最后,结合转移电子光阴极量子效率模型,在给定P型标准InGaAs材料非平衡少子扩散长度分别是0.8、1.0、1.2、1.4、1.6和2.0 mm的条件下,得到对能量在0.780 260~0.820 273 eV区间内、间距为0.002 eV的不同光子能量优化的InP/InGaAs转移电子光阴极吸收层厚度。

Design and calculation of absorption layer thickness on InP/InGaAs transferred-electron photocathode

The electonic structure and optical properties of standard InGaAs material, which formed the absorption layer of transferred-electron InP/InGaAs photocathode, were studied based on the density functional theory, the exchange and correlation potential energy was described by Heyd-Scuseria-Ernzerh(HSE06). First, the energy band structure of zinc blende GaAs was verified with this hybrid density functional, then the standard InGaAs bulk model was established, and dynamically optimized by self-consistent method before complex dielectric function was obtained, then the optical absorption coefficient was derivated from Kramers-Kronig relation. Finally, under the estimation of P-type standard InGaAs unequilibrium minority carriers effusion length were 0.8, 1.0, 1.2, 1.4, 1.6 and 2.0 m separately, combined with quantum efficiency formula of transferred-electron photocathode, the optimized absorption layer thickness of InP/InGaAs photocathode was derivated according to the photon energy between 0.780 260 eV and 0.820 273 eV with spacing 0.002 eV.