Comparative research for GaAs photocathodes with graded compositional AlxGa1−xAs buffer layer
Comparative research for GaAs photocathodes with graded compositional AlxGa1−xAs buffer layer
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DOI：
10.1016/j.optcom.2014.10.004
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发表时间：
2015-03
影响因子：
2.4
通讯作者：
Liang Chen;Yang Shen;Shuqin Zhang;Y. Qian;Sunan Xu
中科院分区：
文献类型：
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作者：
Liang Chen;Yang Shen;Shuqin Zhang;Y. Qian;Sunan Xu
AlxGa 1 −xAs缓冲层中的渐变Al组分结构设计比固定Al组分结构设计能很好地提高量子效率，特别是在短波波段。为了深入研究，采用金属有机化学气相沉积法制备了两种结构的样品，对Cs-O激活前的表面光电压和Cs-O激活后的光谱响应电流进行了对比研究。通过拟合计算和分析，AlxGa 1 −xAs缓冲层中Al组分渐变和GaAs有源层中指数掺杂浓度的混合结构不仅可以在整个窗口层和有源层中形成连续的内电场，而且可以减少AlxGa 1 −xAs/GaAs界面处晶格失配引起的失配位错和层错。与标准结构设计相比，更好的界面特性可以进一步降低背界面复合速度。此外，连续的内电场可以很好地增加活性层的电子扩散和漂移长度以及表面势垒的表面逃逸几率，并可以将缓冲层中更多的短波光激发电子驱动到阴极表面。
The graded Al compositional structure design in AlxGa1−xAs buffer layer can well increase the quantum efficiency than the stationary Al compositional structure design, especially at short-wave band. For deep study, the samples of two structures were prepared by metal organic chemical vapor deposition for carrying out the comparative research between surface photovoltage before Cs–O activation and spectral response current after Cs–O activation. Through fitting calculations and analyzes, the mixed structure of graded Al composition in AlxGa1−xAs buffer layer and exponential doping concentration in GaAs active layer cannot only form continuous internal electric field throughout window layer and active layer, but also decrease the misfit dislocations and stacking faults arising from lattice mismatch at the AlxGa1−xAs/GaAs interface. The better interface properties can further decrease the back interface recombination velocity than the standard structure design. Furthermore the continuous internal electric field can well increase the electron diffusion and drift length for active layer and surface escape probability for surface barriers and can also drive more photo-excited electrons at short-wave band in buffer layer to cathode surface.