Resolution characteristics of graded band-gap reflection-mode AlGaAs/GaAs photocathodes
Resolution characteristics of graded band-gap reflection-mode AlGaAs/GaAs photocathodes
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DOI：
10.1016/j.optcom.2015.08.010
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发表时间：
2015-12
影响因子：
2.4
通讯作者：
Wenjuan Deng;Daoli Zhang;J. Zou;Xincun Peng;Weilu Wang;Yijun Zhang;Benkang Chang
中科院分区：
文献类型：
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作者：
Wenjuan Deng;Daoli Zhang;J. Zou;Xincun Peng;Weilu Wang;Yijun Zhang;Benkang Chang
利用二维泊松方程和连续性方程，通过数值方法计算了渐变带隙AlGaAs/GaAs反射式光电阴极的调制传递函数（MTF）。基于MTF模型，计算了渐变和均匀带隙反射式光电阴极的理论MTF。分析了Al组分、入射光子波长以及AlGaAs和GaAs层厚度对分辨率的影响。计算结果表明，渐变带隙结构可以提高反射式光电阴极的分辨率。当空间频率为800 lp/mm，波长为600 nm时，梯度带隙光电阴极的分辨率一般提高15.4- 29.6%。梯度带隙光电阴极分辨率的提高是由于梯度带隙光电阴极中的内建电场减小了光电子的横向扩散距离。
The modulation transfer function (MTF) of graded band-gap AlGaAs/GaAs reflection-mode photocathodes was determined using two-dimensional Poisson and continuity equations through numerical method. Based on the MTF model, we calculated the theoretical MTF of graded and uniform band-gap reflection-mode photocathodes. We then analyzed the effects of Al composition, wavelength of incident photon, and thicknesses of AlGaAs and GaAs layer on the resolution. Calculation results show that graded band-gap structures can increase the resolution of reflection-mode photocathodes. When the spatial frequency is 800 lp/mm and wavelength is 600 nm, the resolution of graded band-gap photocathodes generally increases by 15.4–29.6%. The resolution improvement of graded band-gap photocathodes is attributed to the fact that the built-in electric field in graded band-gap photocathodes reduces the lateral diffusion distance of photoelectrons.