Interface engineering of InGaAs/InP layer for photocathode
Interface engineering of InGaAs/InP layer for photocathode
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光电阴极 InGaAs/InP 层的界面工程
DOI：
10.1016/j.ijleo.2020.164738
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发表时间：
2020-06-01
期刊：
影响因子：
3.1
通讯作者：
Yang, Mingzhu
中科院分区：
文献类型：
--
作者：
Guo, Jing;Zhao, Jing;Yang, Mingzhu
InGaAs光电阴极通常依靠缓冲层来减轻InGaAs发射层和衬底层之间的晶格失配，从而提高光电发射性能。本文研究了没有缓冲层的InGaAs光电阴极的InGaAs发射层和InP衬底层之间的界面层对光电性能的影响。 GaAs-As-InP模型和GaAs-P-InP模型是根据第一原理建立的。然后，经过能带结构和态密度的计算分析，以As原子层为界面，建立了InGaAs-As-InP模型。通过能带结构和形成能分析发现，InGaAs-As-InP界面能级增加，带隙没有大幅减小，形成能为-10.56 eV/nm2，因此可以形成相对稳定的界面。界面的光学特性表明，InGaAs光电阴极主响应区1000-2000nm波段的反射率和吸收率最低。这有利于发射层吸收光能并产生光电子。界面处的电荷转移导致形成内建电场，该电场从界面向两侧逐渐减弱并从InGaAs发射层指向InP衬底层，有利于界面处产生的光电子传输到发射层表面。对于没有缓冲层的InGaAs光电阴极，其InGaAs-As-InP界面有利于光电子的产生和光电子的传输。制备InGaAs光电阴极时直接在InP衬底层上生长InGaAs发射层可以提高InGaAs光电阴极的光电发射效率。
InGaAs photocathode commonly relies on the buffer layer to mitigate the lattice mismatch between the InGaAs emission layer and the substrate layer and thus enhance the photoemission performance. In this article, the influence of the interface layer between the InGaAs emission layer and the InP substrate layer of the InGaAs photocathode without the buffer layer on the photoemission performance is studied. The GaAs-As-InP model and the GaAs-P-InP model are built based on the First Principle. Then, after the calculation and analysis of the energy band structure and the density of states, As atom layer is used as the interface, based on which the InGaAs-As-InP model is established. It is found by the analysis of energy band structure and formation energy that the energy level is added at the InGaAs-As-InP interface, the band gap is not greatly reduced, and the formation energy is -10.56 eV/nm2, so a relatively stable interface can be formed. The optical properties of the interface show that both the reflectivity and the absorption rate are the lowest in the 1000–2000 nm band of the main response region of the InGaAs photocathode. This is conducive to the absorption of light energy in the emission layer and the generation of photoelectrons. The charge transfer at the interface leads to the formation of a built-in electric field which is gradually weakened from the interface to both sides and directed from the InGaAs emission layer to the InP substrate layer, facilitating the transport of photoelectrons generated at the interface to the surface of the emission layer. For the InGaAs photocathode without the buffer layer, its InGaAs-As-InP interface is beneficial to the generation of photoemission and the transport of photoelectrons. Growing the InGaAs emission layer directly on the InP substrate layer when preparing InGaAs photocathode can improve the photoemission efficiency of the InGaAs photocathode.