Relationship of the longer wavelength threshold and the narrower surface band gap: For GaN and GaAlN photocathodes
Relationship of the longer wavelength threshold and the narrower surface band gap: For GaN and GaAlN photocathodes
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较长波长阈值与较窄表面带隙的关系：对于 GaN 和 GaAlN 光电阴极
DOI：
10.1016/j.ijleo.2016.08.099
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发表时间：
2016-11
期刊：
影响因子：
3.1
通讯作者：
Rao Weifeng
中科院分区：
文献类型：
--
作者：
Yang Mingzhu;Chang Benkang;Rao Weifeng
为了研究GaN和GaAlN光电阴极较长波长阈值的原因，设计并通过MOCVD后Cs/O活化法制备了3个GaN光电阴极和2个GaAlN光电阴极，并对GaN(0001)、Ga0.75Al0.25N(0001)和Ga0.625Al0.375N(0001)表面进行了第一性原理计算。结果表明，计算得出的块体 GaN、Ga0.75Al0.25N 和 Ga0.625Al0.375N 的带隙值分别为 1.630 eV、2.261 eV 和 2.272 eV。同时GaN(0001)、Ga0.75Al0.25N(0001)和Ga0.625Al0.375N(0001)表面的带隙远小于1 eV。讨论了较小表面带隙与较长波长阈值的关系。我们发现表面的晶格参数比块体GaN和GaAlN的晶格参数大，这导致带隙减小。从而从理论上解释了波长阈值较长的现象。
In order to study the cause of the longer-wavelength threshold of GaN and GaAlN photocathodes, three GaN photocathodes and two GaAlN photocathodes were designed and prepared by Cs/O activation following MOCVD, and first-principles calculations about the GaN(0001), Ga0.75Al0.25N(0001), and Ga0.625Al0.375N(0001) surfaces were performed. Results show that the calculated band gap values of the bulk GaN, Ga0.75Al0.25N, and Ga0.625Al0.375N are 1.630 eV, 2.261 eV, and 2.272 eV respectively. Meanwhile the band gap of GaN(0001), Ga0.75Al0.25N(0001) and Ga0.625Al0.375N(0001) surfaces are much smaller than 1 eV. The relation of the smaller surface band gap and the longer-wavelength threshold was discussed. We found that the lattice parameters of the surfaces are larger than those of bulk GaN and GaAlN, which results in the decrease of the band gap. So the phenomenon about the longer wavelength threshold is theoretically explained.
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