Feng Cheng, Zhang Yijun, Qian Yunsheng, Chang Benkang, Shi Feng, Jiao Gangcheng, Zou Jijun
Opt Express. 2015 Jul 27;23(15):19478-88. doi: 10.1364/OE.23.019478.
A heterostructured Al(x)Ga(1-x)As/GaAs photocathode consisting of a composition-graded buffer layer and an exponential-doped emission layer is developed to improve the photoemission performance over the wavelength region of interest. The theoretical quantum efficiency models for reflection-mode and transmission-mode Al(x)Ga(1-x)As/GaAs photocathodes are deduced based on one-dimensional continuity equations, respectively. By comparison of simulated results with conventional quantum efficiency models, it is found that the multilevel built-in electric field can effectively improve the quantum efficiency, which is related to the buffer layer parameters and cathode thicknesses. This special graded bandgap structure arising from the compositional grade in the buffer layer and doping grade in the emission layer would bring about the reduction of back interface recombination losses and the efficient collection of photons generating photoelectrons. Moreover, a best fit of the experimental quantum efficiency data can be achieved with the aid of the deduced models, which would provide an effective approach to evaluate internal parameters for the special graded bandgap photoemitters.
开发了一种由成分渐变缓冲层和指数掺杂发射层组成的异质结构Al(x)Ga(1-x)As/GaAs光电阴极，以提高在感兴趣波长区域的光发射性能。分别基于一维连续性方程推导了反射模式和透射模式Al(x)Ga(1-x)As/GaAs光电阴极的理论量子效率模型。通过将模拟结果与传统量子效率模型进行比较，发现多级内建电场可以有效提高量子效率，这与缓冲层参数和阴极厚度有关。由缓冲层中的成分渐变和发射层中的掺杂渐变产生的这种特殊渐变带隙结构将减少背界面复合损失，并有效收集产生光电子的光子。此外，借助推导的模型可以实现对实验量子效率数据的最佳拟合，这将为评估特殊渐变带隙光发射体的内部参数提供一种有效方法。
