基于Silvaco-ATLAS的Na₂KSb/K₂CsSb/Sb·Cs光阴极光电特性模拟及结构优化

Silvaco-ATLAS-Based Numerical Simulation and Structural Optimization of Photoelectric Performance for Na₂KSb/K₂CsSb/Sb·Cs Photocathodes

摘要: 多碱光阴极是一类以碱金属锑化合物为核心发射材料的高性能光电转换体系，被广泛应用于高灵敏度探测领域。本文基于Silvaco-ATLAS半导体器件仿真平台，建立了三层多碱光阴极结构的数值模型，系统研究了厚度、掺杂和能带参数对量子效率与暗电流的影响。通过引入光生载流子模型、漂移–扩散方程与复合机制，得到了不同波长下的光响应特性和偏压下的电流密度变化规律。对不同Na₂KSb厚度和掺杂浓度的多碱光阴极光电特性进行了比较，对最优结构下的量子效率和暗电流密度进行了分析。结果表明，当Na₂KSb层厚度为100 nm、K₂CsSb层为20 nm、Sb·Cs层为10 nm，并在吸收层掺杂浓度为N_A ≈ 5 × 10¹⁷ cm⁻³时，光阴极的峰值量子效率可达45%，0.3 V偏压下暗电流密度为9 × 10⁻⁷ A/cm²。

Abstract: Multi-alkali photocathodes, which utilize alkali antimonide compounds as the core photoemissive material, represent a class of high-performance photoelectric conversion systems widely employed in high-sensitivity detection. In this paper, a numerical model of a three-layer multi-alkali photocathode structure is established based on the Silvaco-ATLAS semiconductor device simulation platform. The influences of thickness, doping concentration, and band-structure parameters on the quantum efficiency and dark current are systematically investigated. By incorporating the photogenerated carrier model, drift-diffusion equations, and recombination mechanisms, the photoresponse characteristics at different wavelengths and the dependence of current density on bias voltage are obtained. The photoelectric properties of multi-alkali photocathodes with different Na₂KSb thicknesses and doping concentrations are compared, and the quantum efficiency and dark current density under the optimal structure are analyzed. The results show that when the Na₂KSb layer thickness is 100 nm, the K₂CsSb layer is 20 nm, the Sb·Cs layer is 10 nm, and the doping concentration in the absorption layer is N_A ≈ 5 × 10¹⁷ cm⁻³ , the photocathode achieves a peak quantum efficiency of 45% and a dark current density of 9 × 10⁻⁷ A/cm² at 0.3 V bias.