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基于GaN/(BA)2PbI4异质结的自供电双模式紫外探测器

张盛源 夏康龙 张茂林 边昂 刘增 郭宇锋 唐为华

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基于GaN/(BA)2PbI4异质结的自供电双模式紫外探测器

张盛源, 夏康龙, 张茂林, 边昂, 刘增, 郭宇锋, 唐为华

Self-powered dual-mode UV detector based on GaN/(BA)2PbI4 heterojunction

Zhang Sheng-Yuan, Xia Kang-Long, Zhang Mao-Lin, Bian Ang, Liu Zeng, Guo Yu-Feng, Tang Wei-Hua
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  • 紫外探测器作为智能光电系统的重要组成部分, 近年来在诸多领域应用广泛, 其中自供电异质结光电二极管的研究显得尤为重要. 本文制备并讨论了一种双模式运行的GaN/(BA)2PbI4异质结紫外光电二极管. 通过金属有机化学气相沉积法在蓝宝石上沉积GaN薄膜, 再在GaN薄膜表面旋涂(BA)2PbI4薄膜, 用于构建平面异质结探测器. 当在+5 V偏压驱动、光强为421 μW/cm2的365 nm紫外光照射下, 响应度(R)和外量子效率(EQE)分别为60 mA/W和20%. 在自供电模式下, 上升时间(τr)和衰减时间(τd)分别为0.12 s和0.13 s. 这些结果共同证明了基于GaN/(BA)2PbI4异质结的自供电紫外光电二极管拥有旷阔的发展前景, 为智能光电系统的发展提供了新的思路.
    As an important part of an intelligent photoelectric system, ultraviolet detector has been widely used in many fields in recent years. The research on self-powered heterojunction photodiode is particularly important. In this work, a dual-mode self-powered GaN/(BA)2PbI4 heterojunction ultraviolet photodiode is prepared and discussed. The GaN film is deposited on sapphire by metal-organic chemical vapor deposition, and then the (BA)2PbI4 film is spin-coated onto the surface of the GaN film to construct a planar heterojunction detector. The X-ray diffraction, energy-dispersive X-ray spectroscopy mapping and scanning electron microscope measurements are used to determine the quality of GaN and (BA)2PbI4 thin films. When the film is illuminated by 365 nm light with a power density of 421 μW/cm2 at 5 V bias, the responsiveness (R) and external quantum efficiency (EQE) are 60 mA/W and 20%, respectively. In self-powered mode, the rise time (τr) and decay time (τd) are 0.12 s and 0.13 s, respectively, illustrating the fast photogeneration process and recombination process for photo-excited electron-hole pairs. And, the R is 1.96×10–4 mA/W, owing to the development of space charge region across the interface of GaN thin film and (BA)2PbI4 thin film. The outcomes of this study unequivocally demonstrate the extensive potential and wide-ranging applicability of self-powered UV photodiodes based on the GaN/(BA)2PbI4 heterojunction configuration. Moreover, this research presents a new concept that provides a novel avenue to the ongoing development of intelligent optoelectronic systems.
      通信作者: 张茂林, mlzhang@njupt.edu.cn ; 边昂, angbian@just.edu.cn ; 刘增, zengliu@njupt.edu.cn
    • 基金项目: 国家重点研发计划(批准号: 2022YFB3605404)、国家自然科学基金联合基金(批准号: U23A20349)、国家自然科学基金青年科学基金(批准号: 62204125, 62304113, 62305135)和南京邮电大学引进人才科研启动基金 (自然科学) (批准号: XK1060921115, XK1060921002)资助的课题.
      Corresponding author: Zhang Mao-Lin, mlzhang@njupt.edu.cn ; Bian Ang, angbian@just.edu.cn ; Liu Zeng, zengliu@njupt.edu.cn
    • Funds: Project supported by the National Key R&D Program of China (Grant No. 2022YFB3605404), the Joint Funds of the National Natural Science Foundation of China (Grant No. U23A20349), the Young Scientist Fund of the National Natural Science Foundation of China (Grant Nos. 62204125, 62304113, 62305135), and the Natural Science Research Start-up Foundation of Recruiting Talents of Nanjing University of Posts and Telecommunications, China (Grant Nos. XK1060921115, XK1060921002).
    [1]

    Zhang S, Wei S, Liu Z, Li T, Li C, Huang X L, Wang C, Xie Z, Al-Hartomy O A, Al-Ghamdi A A, Wageh S, Gao J, Tang Y, Wang H, Wang Q, Zhang H 2022 Mater. Today Phys. 27 100812Google Scholar

    [2]

    Xie C, Lu X T, Tong X W, Zhang Z X, Liang F X, Liang L, Luo L B, Wu Y C 2019 Adv. Funct. Mater. 29 1806006Google Scholar

    [3]

    Monroy E, Omnès F, Calle F 2003 Semicond. Sci. Technol. 18 R33Google Scholar

    [4]

    Zheng W, Huang F, Zheng R, Wu H 2015 Adv. Mater. 27 3921Google Scholar

    [5]

    Liu Z, Tang W 2023 J. Phys. D: Appl. Phys. 56 093002

    [6]

    Su L, Yang W, Cai J, Chen H, Fang X 2017 Small 13 1701687Google Scholar

    [7]

    Jiang W Y, Liu Z, Li S, Yan Z Y, Lu C L, Li P G, Guo Y F, Tang W H 2021 IEEE Sens. J. 21 18663Google Scholar

    [8]

    Zhao B, Wang F, Chen H, Zheng L, Su L, Zhao D, Fang X 2017 Adv. Funct. Mater. 27 1700264Google Scholar

    [9]

    Song W, Chen J, Li Z, Fang X 2021 Adv. Mater. 33 2101059Google Scholar

    [10]

    Zuo C, Cai S, Li Z, Fang X 2021 Nanotechnology 33 105202

    [11]

    Li L, Liu Z, Tang K, Sha S L, Zhang S H, Jiang M M, Zhang M L, Bian A, Guo Y F, Tang W H 2023 IEEE Sens. J. 23 12767Google Scholar

    [12]

    Lan Z, Lei Y, Chan W K E, Chen S, Luo D, Zhu F 2020 Sci. Adv. 6 eaaw8065Google Scholar

    [13]

    Hu X, Liu H, Wang X, Zhang X, Shan Z, Zheng W, Li H, Wang X, Zhu X, Jiang Y, Zhang Q, Zhuang X, Pan A 2018 Adv. Opt. Mater. 6 1800293Google Scholar

    [14]

    Lan Z, Lau Y S, Cai L, Han J, Suen C W, Zhu F 2022 Laser Photonics Rev. 16 2100602Google Scholar

    [15]

    Sun W M, Sun B Y, Li S, Ma G L, Gao A, Jiang W Y, Zhang M L, Li P G, Liu Z, Tang W H 2022 Chin. Phys. B 31 024205Google Scholar

    [16]

    Ma G, Jiang W, Sun W, Yan Z, Sun B, Li S, Zhang M, Wang X, Gao A, Dai J, Liu Z, Li P, Tang W 2021 Phys. Scr. 96 125823Google Scholar

    [17]

    Xu T, Jiang M, Wan P, Liu Y, Kan C, Shi D 2023 J. Mater. Sci. Technol. 138 183Google Scholar

    [18]

    Tang K, Jiang M, Yang B, Xu T, Liu Z, Wan P, Kan C, Shi D 2023 Nanoscale 15 2292Google Scholar

    [19]

    Li L, Ye S, Qu J, Zhou F, Song J, Shen G 2021 Small 17 2005606Google Scholar

    [20]

    Lee J, Baek K, Lee J, Ahn H, Kim Y, Lim H, Kim Y, Woo J, Stranks S D, Lee S K, Sirringhaus H, Kang K, Lee T 2023 Adv. Funct. Mater. 33 2302048Google Scholar

    [21]

    Xia J, Gu H, Liang C, Cai Y, Xing G 2022 J. Phys. Chem. Lett. 13 4579Google Scholar

    [22]

    Senthil Kumar M, Kumar J 2003 Mater. Chem. Phys. 77 341Google Scholar

    [23]

    Cao D H, Stoumpos C C, Farha O K, Hupp J T, Kanatzidis M G 2015 J. Am. Chem. Soc. 137 7843Google Scholar

    [24]

    Lin Y, Bai Y, Fang Y, Chen Z, Yang S, Zheng X, Tang S, Liu Y, Zhao J, Huang J 2018 J. Phys. Chem. Lett. 9 654Google Scholar

    [25]

    Xia J, Liang C, Gu H, Mei S, Cai Y, Xing G 2022 ACS Appl. Electron. Mater. 4 1939Google Scholar

    [26]

    Liu Z, Du L, Zhang S H, Li L, Xi Z Y, Tang J C, Fang J P, Zhang M L, Yang L L, Li S, Li P G, Guo Y F, Tang W H 2022 IEEE Trans. Electron Devices 69 5595Google Scholar

    [27]

    Zhu H, Shan C X, Yao B, Li B H, Zhang J Y, Zhao D X, Shen D Z, Fan X W 2008 J. Phys. Chem. C 112 20546Google Scholar

    [28]

    Mishra M, Gundimeda A, Krishna S, Aggarwal N, Goswami L, Gahtori B, Bhattacharyya B, Husale S, Gupta G 2018 ACS Omega 3 2304Google Scholar

    [29]

    Lee C T, Lin T S, Lee H Y 2010 IEEE Photonics Technol. Lett. 22 1117Google Scholar

    [30]

    Prakash N, Singh M, Kumar G, Barvat A, Anand K, Pal P, Singh S P, Khanna S P 2016 Appl. Phys. Lett. 109 242102Google Scholar

    [31]

    Zhou H, Gui P, Yang L, Ye C, Xue M, Mei J, Song Z, Wang H 2017 New J. Chem. 41 4901Google Scholar

    [32]

    王顺利, 王亚超, 郭道友, 李超荣, 刘爱萍 2021 物理学报 70 128502Google Scholar

    Wang S L, Wang Y C, Guo D Y, Li C R, Liu A P 2021 Acta Phys. Sin. 70 128502Google Scholar

  • 图 1  (a) 异质结的SEM图像, 内插图为GaN/(BA)2PbI4异质结的XRD图谱; (b) 异质结的EDS元素图; (c) GaN/(BA)2PbI4异质结的能谱; (d) (BA)2PbI4薄膜的SEM图; (e) GaN薄膜的SEM图

    Fig. 1.  (a) SEM image of heterojunction, inset shows the XRD patterns of GaN/(BA)2PbI4 heterojunction; (b) EDS elemental maps of heterojunction; (c) energy spectrum of GaN/(BA)2PbI4 heterojunction; (d) SEM image of (BA)2PbI4 thin film; (e) SEM image of GaN thin film.

    图 2  (a), (b) (αhν)2与()的拟合函数图; (c) GaN/(BA)2PbI4异质结的紫外-可见光响应谱

    Fig. 2.  (a), (b) Plot of (αhν)2 as a function of photon energy (); (c) the UV-vis response spectrum of the GaN/(BA)2PbI4 heterojunction.

    图 3  (a) GaN/(BA)2PbI4 异质结光电探测器示意图; (b) 异质结光电探测器在黑暗中和不同强度的365 nm紫外光照明下的对数坐标I-V特性曲线; (c), (d) 在不同电压下探测器的PDCR和光强度的关系; (e), (f) 在不同电压下响应度(R)和外部量子效率(EQE)与光强度的关系

    Fig. 3.  (a) Schematic diagram of the GaN/(BA)2PbI4 heterojunction photodetector; (b) I-V characteristics in a log coordinate of the heterojunction photodetector in the dark and under 365 nm UV light illumination with various intensities; (c), (d) PDCR of the PD replying on the light intensity under various voltages; (e), (f) responsivity (R) and external quantum efficiency (EQE) replying on the light intensity under various voltages.

    图 4  GaN和(BA)2PbI4的电流-电压特性曲线.

    Fig. 4.  Current-voltage curves of GaN and (BA)2PbI4.

    图 5  在 365 nm紫外光照射下(a)正电压和(b)负电压下的 I-t 曲线, (a)的插图显示了 1 V 下的 I-t 曲线; (c)零偏置时365 nm 光照下的 I-t 曲线, 插图显示了器件在 365 nm 光照射下的瞬态响应, 零偏置时的功率密度为 113 μW/cm2; (d) 零偏置时异质结光电探测器的带状图

    Fig. 5.  The I-t curves at (a) positive voltages and (b) negative voltages under the illuminations of 356 nm UV light, inset of (a) shows the I-t curves at 1 V; (c) the I-t curves under 365 nm light illumination at zero bias, inset shows transient responses of the devices under the 365 nm light illumination with a power density of 113 μW/cm2 at zero bias; (d) the band diagram of the heterojunction photodetector at zero bias.

    表 1  基于GaN/(BA)2PbI4异质结的光电二极管紫外探测器性能参数比较

    Table 1.  Parameters comparison of self-powered GaN/(BA)2PbI4 heterojunction UV photodiode

    Photodetector Bias voltage/V Wavelength/nm R/(mA·W–1) Rise/Decay time/s Ref.
    n-ZnO/p-GaN 0 374 1×10–3 N/A [27]
    GaN nanorods 3 325 26 0.33/0.99 [28]
    GaN/ZnO/ZnO –5 360 90 N/A [29]
    r-GO/GaN 0 350 1.54 0.06/0.267 [30]
    ZnO/CdS/GaN 0 300 176 0.35 [31]
    GaN/(BA)2PbI4 0 365 1.96×10–4 0.12/0.13 This work
    GaN/(BA)2PbI4 +5 365 60 N/A This work
    下载: 导出CSV
  • [1]

    Zhang S, Wei S, Liu Z, Li T, Li C, Huang X L, Wang C, Xie Z, Al-Hartomy O A, Al-Ghamdi A A, Wageh S, Gao J, Tang Y, Wang H, Wang Q, Zhang H 2022 Mater. Today Phys. 27 100812Google Scholar

    [2]

    Xie C, Lu X T, Tong X W, Zhang Z X, Liang F X, Liang L, Luo L B, Wu Y C 2019 Adv. Funct. Mater. 29 1806006Google Scholar

    [3]

    Monroy E, Omnès F, Calle F 2003 Semicond. Sci. Technol. 18 R33Google Scholar

    [4]

    Zheng W, Huang F, Zheng R, Wu H 2015 Adv. Mater. 27 3921Google Scholar

    [5]

    Liu Z, Tang W 2023 J. Phys. D: Appl. Phys. 56 093002

    [6]

    Su L, Yang W, Cai J, Chen H, Fang X 2017 Small 13 1701687Google Scholar

    [7]

    Jiang W Y, Liu Z, Li S, Yan Z Y, Lu C L, Li P G, Guo Y F, Tang W H 2021 IEEE Sens. J. 21 18663Google Scholar

    [8]

    Zhao B, Wang F, Chen H, Zheng L, Su L, Zhao D, Fang X 2017 Adv. Funct. Mater. 27 1700264Google Scholar

    [9]

    Song W, Chen J, Li Z, Fang X 2021 Adv. Mater. 33 2101059Google Scholar

    [10]

    Zuo C, Cai S, Li Z, Fang X 2021 Nanotechnology 33 105202

    [11]

    Li L, Liu Z, Tang K, Sha S L, Zhang S H, Jiang M M, Zhang M L, Bian A, Guo Y F, Tang W H 2023 IEEE Sens. J. 23 12767Google Scholar

    [12]

    Lan Z, Lei Y, Chan W K E, Chen S, Luo D, Zhu F 2020 Sci. Adv. 6 eaaw8065Google Scholar

    [13]

    Hu X, Liu H, Wang X, Zhang X, Shan Z, Zheng W, Li H, Wang X, Zhu X, Jiang Y, Zhang Q, Zhuang X, Pan A 2018 Adv. Opt. Mater. 6 1800293Google Scholar

    [14]

    Lan Z, Lau Y S, Cai L, Han J, Suen C W, Zhu F 2022 Laser Photonics Rev. 16 2100602Google Scholar

    [15]

    Sun W M, Sun B Y, Li S, Ma G L, Gao A, Jiang W Y, Zhang M L, Li P G, Liu Z, Tang W H 2022 Chin. Phys. B 31 024205Google Scholar

    [16]

    Ma G, Jiang W, Sun W, Yan Z, Sun B, Li S, Zhang M, Wang X, Gao A, Dai J, Liu Z, Li P, Tang W 2021 Phys. Scr. 96 125823Google Scholar

    [17]

    Xu T, Jiang M, Wan P, Liu Y, Kan C, Shi D 2023 J. Mater. Sci. Technol. 138 183Google Scholar

    [18]

    Tang K, Jiang M, Yang B, Xu T, Liu Z, Wan P, Kan C, Shi D 2023 Nanoscale 15 2292Google Scholar

    [19]

    Li L, Ye S, Qu J, Zhou F, Song J, Shen G 2021 Small 17 2005606Google Scholar

    [20]

    Lee J, Baek K, Lee J, Ahn H, Kim Y, Lim H, Kim Y, Woo J, Stranks S D, Lee S K, Sirringhaus H, Kang K, Lee T 2023 Adv. Funct. Mater. 33 2302048Google Scholar

    [21]

    Xia J, Gu H, Liang C, Cai Y, Xing G 2022 J. Phys. Chem. Lett. 13 4579Google Scholar

    [22]

    Senthil Kumar M, Kumar J 2003 Mater. Chem. Phys. 77 341Google Scholar

    [23]

    Cao D H, Stoumpos C C, Farha O K, Hupp J T, Kanatzidis M G 2015 J. Am. Chem. Soc. 137 7843Google Scholar

    [24]

    Lin Y, Bai Y, Fang Y, Chen Z, Yang S, Zheng X, Tang S, Liu Y, Zhao J, Huang J 2018 J. Phys. Chem. Lett. 9 654Google Scholar

    [25]

    Xia J, Liang C, Gu H, Mei S, Cai Y, Xing G 2022 ACS Appl. Electron. Mater. 4 1939Google Scholar

    [26]

    Liu Z, Du L, Zhang S H, Li L, Xi Z Y, Tang J C, Fang J P, Zhang M L, Yang L L, Li S, Li P G, Guo Y F, Tang W H 2022 IEEE Trans. Electron Devices 69 5595Google Scholar

    [27]

    Zhu H, Shan C X, Yao B, Li B H, Zhang J Y, Zhao D X, Shen D Z, Fan X W 2008 J. Phys. Chem. C 112 20546Google Scholar

    [28]

    Mishra M, Gundimeda A, Krishna S, Aggarwal N, Goswami L, Gahtori B, Bhattacharyya B, Husale S, Gupta G 2018 ACS Omega 3 2304Google Scholar

    [29]

    Lee C T, Lin T S, Lee H Y 2010 IEEE Photonics Technol. Lett. 22 1117Google Scholar

    [30]

    Prakash N, Singh M, Kumar G, Barvat A, Anand K, Pal P, Singh S P, Khanna S P 2016 Appl. Phys. Lett. 109 242102Google Scholar

    [31]

    Zhou H, Gui P, Yang L, Ye C, Xue M, Mei J, Song Z, Wang H 2017 New J. Chem. 41 4901Google Scholar

    [32]

    王顺利, 王亚超, 郭道友, 李超荣, 刘爱萍 2021 物理学报 70 128502Google Scholar

    Wang S L, Wang Y C, Guo D Y, Li C R, Liu A P 2021 Acta Phys. Sin. 70 128502Google Scholar

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    [20] 李书平, 王仁智, 郑永梅, 蔡淑惠, 何国敏. 平均键能方法在应变层异质结带阶研究中的应用. 物理学报, 2000, 49(8): 1441-1446. doi: 10.7498/aps.49.1441
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出版历程
  • 收稿日期:  2023-10-25
  • 修回日期:  2023-12-14
  • 上网日期:  2023-12-29
  • 刊出日期:  2024-03-20

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