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AlGaAs光电阴极具有响应速度快和光谱响应范围可调的特性, 可被应用于水下光通信领域. 为了解决AlGaAs发射层较低的光吸收限制其量子效率提高的问题, 利用分布式布拉格反射镜(DBR)结构对特定波长光的反射作用, 将透过光重新反射回发射层进一步提高吸收率, 从而增强阴极在532 nm波长处的响应能力. 通过求解一维连续性方程, 建立了具有DBR结构的AlGaAs光电阴极光谱响应模型. 采用时域有限差分法, 分析了DBR结构中子层周期对数、子层材料以及发射层、缓冲层厚度对发射层吸收率的影响, 对比了有无DBR结构AlGaAs光电阴极的光吸收分布. 结果表明, 周期对数为20、子层材料为Al0.7Ga0.3As/AlAs的DBR结构对532 nm光的反射效果最优. 基于该DBR结构, 发射层和缓冲层厚度分别为495 nm和50 nm时, 发射层对532 nm光具有最佳吸收率. 通过对外延生长的AlGaAs光电阴极进行激活实验, 结果表明具有DBR结构的AlGaAs光电阴极在532 nm波长处的光谱响应率相比无DBR结构的AlGaAs光电阴极光谱响应率提升了约1倍.
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关键词:
- AlGaAs光电阴极 /
- 分布式布拉格反射镜 /
- 光谱响应 /
- 光吸收
The AlGaAs photocathode can be used in the field of underwater optical communication because of its fast response speed and adjustable spectral response range. In order to solve the problem that the low light absorption of the AlGaAs emission layer limits the improvement of its quantum efficiency, the distributed Bragg reflector (DBR) structure is used to reflect the light at a specific wavelength back to the emission layer to further increase the absorption rate, thus improving the response capability of the photocathode at 532 nm. The spectral response model of the AlGaAs photocathode with DBR structure is obtained by solving one-dimensional continuity equation. The optical model of the AlGaAs photocathode with enhanced response at 532 nm is established by the finite-difference time-domain method. The effects of the sublayer periodic pairs, the sublayer material and the thickness of emission layer and buffer layer on the absorption rate of emission layer are analyzed. The light absorption distributions of AlGaAs photocathode with and without DBR structure are compared, and the influence mechanism of DBR structure on the blue-green light absorption capacity of AlGaAs photocathode emission layer is clarified, which can provide a theoretical basis for designing its structural parameters. The results show that the DBR structure with a periodic pair of 20 and Al0.7Ga0.3As/AlAs has the best reflection effect on 532 nm light. Based on the DBR structure, when the thickness of the emission layer and buffer layer are 495 nm and 50 nm, respectively, the emission layer has the best absorption rate of 532 nm light. Furthermore, two kinds of AlGaAs photocathodes with and without DBR structure are prepared by the metal-organic chemical vapor deposition technology, and the reflectivity and profile structure of the grown samples are characterized. Then the Cs/O activation experiments are performed to compare the spectral response curves. It is found that the spectral response of the AlGaAs photocathode sample with DBR structure at 532 nm wavelength is about twice that of the sample without DBR structure.-
Keywords:
- AlGaAs photocathode /
- distributed Bragg reflector /
- spectral response /
- optical absorption
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图 1 AlGaAs光电阴极结构示意图 (a) 设计的自上而下结构; (b) 传统结构与设计结构的光路对比
Fig. 1. Structure diagram of AlGaAs photocathode: (a) The designed top-down structure; (b) comparison of the optical path between the traditional structure and the designed structure.
图 3 不同子层交替对数的DBR层反射谱
Fig. 3. Reflectivity of DBR layer with different sublayer alternating pairs.
图 4 DBR层的光学性质 (a) 不同子层材料的反射谱; (b) 不同子层材料的消光系数
Fig. 4. Optical properties of DBR layer: (a) Reflectivity for different sublayer materials; (b) extinction coefficient of different sublayer materials.
图 5 发射层吸收率随阴极厚度的变化 (a) 发射层厚度; (b) 缓冲层厚度
Fig. 5. Variation of emission layer absorptivity with cathode thickness: (a) Different emission layer thickness Le; (b) different buffer layer thickness Lb.
图 6 有无DBR结构情况下的AlGaAs光电阴极在532 nm处的光吸收强度分布图
Fig. 6. Optical absorption intensity distribution at 532 nm of AlGaAs photocathodes with or without DBR structure.
图 7 结构A与结构B阴极样品SEM图
Fig. 7. SEM images of cathode samples with structure A and structure B.
图 8 (a)结构A与(b)结构B阴极样品反射率实测、理论和拟合结果对比图
Fig. 8. Comparison of measured, theoretical and fitting results of reflectivity of cathode samples with (a) structure A and (b) structure B.
图 9 (a)结构A与(b)结构B 阴极样品的Cs/O激活光电流曲线
Fig. 9. Cs/O activation photocurrent curves of cathode samples with structure A and structure B.
图 10 结构A与结构B 阴极样品的光谱响应实测和拟合曲线与反射率实测曲线
Fig. 10. Measured and fitted spectral response curves and measured reflectivity curves of cathode samples with structure A and structure B.
表 1 阴极样品结构参数拟合结果
Table 1. Fitting results of structure parameters of the cathode samples.
材料 结构A 结构B 设计值/nm 实际值/nm 设计值/nm 实际值/nm Al0.63Ga0.37As发射层 495 500 495 522 Al0.8Ga0.2As缓冲层 50 60 50 60 DBR层Al0.7Ga0.3As子层 36 34.9 — — DBR层AlAs子层 41 38.8 — — 
下载: 导出CSV
表 2 阴极性能参量拟合结果
Table 2. Fitting results of cathode performance parameters.
结构A 结构B 描述 P0 0.36 0.25 表面电子逸出概率 K 0.2 0.6 表面势垒因子 Sv/(cm·s–1) 4×104 1×105 后界面电子复合速率
下载: 导出CSV
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[1] Guo X, Shi F, Jia T T, Zhang R Y, Du J J, Chen P, Wu H Y, Cheng H C, Zhang Y J 2023 IEEE Photonics J. 15 6801005
Google Scholar
[2] Schindler P, Riley D C, Bargatin I, Sahasrabuddhe K, Schwede J W, Sun S, Pianetta P, Shen Z X, Howe R T, Melosh N A 2019 ACS Energy Lett. 4 2436
Google Scholar
[3] Bae J K, Andorf M, Bartnik A, Galdi A, Cultrera L, Maxson J, Bazarov I 2022 AIP Adv. 12 095017
Google Scholar
[4] 梁羽铁, 杨一玻, 赵宇翔 2020 物理 49 525
Google Scholar
Liang Y T, Yang Y B, Zhao Y X 2020 Physics 49 525
Google Scholar
[5] Morishita H, Ohshima T, Otsuga K, Kuwahara M, Agemura T, Ose Y 2021 Ultramicroscopy 230 113386
Google Scholar
[6] Chen X L, Tang G H, Wang D C, Xu P X 2018 Opt. Mater. Express 8 3155
Google Scholar
[7] Xu Y, Zhang Y J, Feng C, Shi F, Zou J J, Chen X L, Chang B K 2016 Opt. Commun. 380 320
Google Scholar
[8] Nishitani T, Tabuchi M, Takeda Y, Suzuki Y, Motoki K, Meguro T 2009 Jpn. J. Appl. Phys. 48 06FF02
Google Scholar
[9] Spagnolo G S, Cozzella L, Leccese F 2020 Sensors 20 2261
Google Scholar
[10] Kaushal H, Kaddoum G 2016 IEEE Access 4 1518
Google Scholar
[11] 曾凤娇, 杨康建, 晏旭, 赵孟孟, 杨平, 文良华 2021 激光与光电子学进展 58 0300002
Google Scholar
Zeng F J, Yang K J, YAN X, Zhao M M, Yang P, Wen L H 2021 Laser Optoelectron. Prog. 58 0300002
Google Scholar
[12] 李坤, 杨苏辉, 廖英琦, 林学彤, 王欣, 张金英, 李卓 2021 70 084203
Google Scholar
Li K, Yang S H, Liao Y Q, Lin X T, Wang X, Zhang J Y, Li Z 2021 Acta Phys. Sin. 70 084203
Google Scholar
[13] Chen X L, Zhao J, Chang B K, Yu X H, Hao G H, Xu Y, Cheng H C 2013 J. Appl. Phys. 113 213105
Google Scholar
[14] Chen X L, Jin M C, Zeng Y G, Hao G H, Zhang Y J, Chang B K, Shi F, Cheng H C 2014 Appl. Opt. 53 7709
Google Scholar
[15] Chen X L, Zhao J, Chang B K, Hao G H, Xu Y, Zhang Y J, Jin M C 2014 Mater. Sci. Semicond. Process. 18 122
Google Scholar
[16] Li S M, Zhang Y J, Wang Z H, Wang D Z, Tang S, Zhang J J, Shi F, Jiao G C, Cheng H C, Hao G H 2023 Opt. Express 31 26014
Google Scholar
[17] Spicer W E 1977 Appl. Phys. 12 115
Google Scholar
[18] Xia J, Beomhoan O, Lee S G, Lee E 2005 Opt. Laser Technol. 37 125
Google Scholar
[19] Wang S C, Lu T C, Kao C C, Chu J T, Huang G S, Kuo H C, Chen S W, Kao T T, Chen J R, Lin L F 2007 Jpn. J. Appl. Phys. 46 5397
Google Scholar
[20] Liu L J, Wu Y D, Wang Y, An J M, Hu X W 2018 Optoelectron. Lett. 14 342
Google Scholar
[21] Jahed M, Gustavsson J S, Larsson A 2021 IEEE J. Quantum Electron. 57 2400307
Google Scholar
[22] Martinelli R U, Fisher D G 1974 Proc. IEEE 62 1339
Google Scholar
[23] Zou J J, Chang B K, Chen H L, Liu L 2007 J. Appl. Phys. 101 033126
Google Scholar
[24] Liu W, Chen Y Q, Lu W T, Moy A, Poelker M, Stutzman M, Zhang S K 2016 Appl. Phys. Lett. 109 252104
Google Scholar
[25] Sun X J, Hu L Z, Song H, Li Z M, Li D B, Jiang H, Miao G Q 2009 Solid State Electron 53 1032
Google Scholar
[26] Chen X L, Chang B K, Zhao J, Hao G H, Jin M C, Xu Y 2013 Opt. Commun. 309 323
Google Scholar
[27] Zhang Y J, Zhang K M, Li S M, Li S, Qian Y S, Shi F, Jiao G C, Miao Z, Guo Y L, Zeng Y G 2020 J. Appl. Phys. 128 173103
Google Scholar
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