透射式GaAs光电阴极时间分辨特性研究

时间分辨特性是GaAs光电阴极应用于泵浦探测等领域的一种极为重要的性能参量。采用矩阵差分求解光电子扩散模型的方式计算了光电子连续性方程和出射光电子流密度方程，发现影响GaAs光电阴极时间分辨特性的因素包括GaAs/GaAlAs后界面复合速率、GaAs电子扩散系数和GaAs激活层厚度，之后较为系统地研究了这三种物理因素对GaAs光电阴极时间分辨特性的影响。研究结果表明，GaAs电子扩散系数和GaAs/GaAlAs后界面复合速率与光电阴极的响应速率存在非线性正比关系，且随着两者的增大，GaAs光电阴极将出现饱和响应速率。激活层厚度对GaAs光电阴极响应时间的影响最大，通过激活层厚度的适当减薄可以将GaAs光电阴极的响应时间缩短至20 ps，可满足绝大多数光子、粒子探测的快响应需求。该研究为快响应GaAs光电阴极的实验和应用提供了必要的理论支撑。

Study on the time-resolved characteristics of the transmission-mode GaAs photocathode

Time-resolved characteristics are a very important performance parameter of GaAs photocathodes used in pump detection and other fields. In this paper, the photoelectron continuity equation and the outgoing photoelectron flow density equation are calculated by solving the photoelectron diffusion model by the matrix difference method. The factors affecting the time-resolved characteristics of the GaAs photocathode include the recombination rate of the GaAs/GaAlAs rear interface, GaAs electron diffusion coefficient and GaAs active layer thickness. Then, the effects of these three physical factors on the time-resolved characteristics of the GaAs photocathode are systematically studied. The research results show that the GaAs electron diffusion coefficient and the GaAs/GaAlAs rear interface recombination rate have a nonlinear proportional relationship with the response rate of the photocathode, and the saturation response rate of the GaAs photocathode will appear as the two increase. The thickness of the GaAs active layer has the greatest impact on the response time of the GaAs photocathode. The response time of the GaAs photocathode can be reduced to 20 ps by appropriately thinning the thickness of the active layer, which can meet the fast response requirements for most photon and particle detection. This study provides necessary theoretical support for the experiment and application of a fast-response GaAs photocathode.