本論文主要探討利用超音波噴霧熱裂解法沉積法製備氧化鋁鎵應用於紫外光檢測器。超音波噴霧熱裂解沉積法是一種成本低廉、非真空、製成時間短且易於調變前驅物內容物濃度之薄膜沉積技術。我們將該技術應用於紫外光檢測器上製作金屬-半導體-金屬( MSM )結構。在此研究中，我們通過調整前驅體溶液中乙酰丙酮鋁之摩爾比例以比較其所沉積薄膜的特性。X-射線繞射分析結果顯示本研究所沉積之薄膜均為α相。另外觀察Tauc plot後可發現通過調整前驅體溶液中乙烯丙酮鋁之摩爾比例能有限度調變薄膜之能隙。藉由XPS分析結果可知當前驅體溶液中乙烯丙酮鋁之摩爾比例增加，其薄膜中將產生更多的氧空缺。通過元件電性分析比較我們得知當前驅體溶液中乙烯丙酮鋁之摩爾比例為0.4時，基於其薄膜之光檢測器有最優異之表現。由於有著寬能隙及大量氧空缺作為載流子，因此展現了卓越的光暗電流比(4.74x106)與響應度(1918.6A/W)，此外其深紫外光-可見光拒斥比高達(8.4x104)，表現出很好的對於深紫外光(UVC)的選擇性。同時由於表面較為緻密，因此元件之響應速度十分優秀，分別為上升時間1.29s /下降時間0.11s。
此外為了解決實驗器材對沉積溫度之限制，我們分別採用兩種替代方式，希望能藉此幫助鋁前驅體的分解，進而提升薄膜中鋁含量，從而實現具更寬能隙之氧化鋁鎵薄膜。然而實驗結果發現過高的溫度與長時間的加熱將導致薄膜中發生相轉變，進而使元件之電學表現下降。在本論文中，我們以超音波噴霧熱裂解沉積法製備的氧化鋁鎵深紫外光檢測器相對於其他沉積方法展現出卓越之電性表現。

This study primarily investigates the application of the ultrasonic spray pyrolysis method for depositing aluminum gallium oxide (Al1-xGa1-x)2O3 films for use in ultraviolet (UV) photodetectors. The ultrasonic spray pyrolysis method is a cost-effective, non-vacuum deposition technique that allows for easy modulation of precursor solution concentration and short fabrication time. In this research, we compare the characteristics of the deposited films by adjusting the molar ratio of aluminum acetylacetonate in the precursor solution. X-ray diffraction analysis confirms that all the deposited films in this study exhibit the α-phase structure. Tauc plot analysis reveals that the bandgap of the films can be selectively modulated by adjusting the molar ratio of aluminum acetylacetonate in the precursor solution. X-ray photoelectron spectroscopy analysis indicates that an increased molar ratio of aluminum acetylacetonate in the precursor solution leads to a higher concentration of oxygen vacancies in the films.
Based on the electrical characterization of the devices, it is observed that the photodetector based on the film deposited with a molar ratio of 0.4 exhibits the best performance. This film, with its wide bandgap and abundant oxygen vacancies as carriers, demonstrates high photocurrent-to-dark current ratio (4.74 × 106) and responsivity (1918.6 A/W) as well as a high deep UV-visible rejection ratio (8.4 × 104), indicating good selectivity for deep ultraviolet light (UVC). Moreover, due to its compact surface, the device exhibits excellent response speed with rise and fall time of 1.29 s and 0.11 s, respectively.
In order to overcome the limitations imposed by the deposition temperature of the experimental setup, two alternative approaches were employed to facilitate the decomposition of the aluminum precursor and enhance the aluminum content in the film, aiming to achieve wider bandgap aluminum gallium oxide films. However, the experimental results revealed that excessively high temperature and prolonged heating ledto phase transitions in the films and consequently deteriorated the electrical performance of the devices.
In this study, the (Al1-xGa1-x)2O3 deep UV photodetectors prepared using the ultrasonic spray pyrolysis method exhibited superior electrical performances compared to other deposition methods.

[1] H. Shen, C.X. Shan, B.H. Li, B. Xuan, and D.Z. Shen, “Reliable self-powered highly spectrum-selective ZnO ultraviolet photodetectors,” Appl. Phys. Lett., vol. 103, no. 23, pp. 232112-1–232112-4, Dec. 2013.
[2] S.P. Chang , S.J. Chang , Y.Z. Chiou , C.Y. Lu , T.K. Lin , Y.C. Lin , C.F. Kuo , H.M. Chang, “ZnO photoconductive sensors epitaxially grown on sapphire substrates,” Sensors Actuators A, vol. 140, no. 1, pp. 60–64, Oct. 2007.
[3] S.J. Young, L.W. Ji, T.H. Fang, S.J. Chang, Y.K. Su, and X.L. Du, “ZnO ultraviolet photodiodes with Pd contact electrodes,” Acta Materialia, vol. 55, no. 1, pp. 329–333, Jan. 2007.
[4] C.K. Wang, S.J. Chang, Y.K. Su, Y.Z. Chiou, S.C. Chen, C.S. Chang, T.K. Lin, H.L. Liu, J.J. Tang, “GaN MSM UV photodetectors with titanium tungsten transparent electrodes,” IEEE Trans. Electron. Devices, vol. 53, no. 1, pp. 38–42, Jan. 2006.
[5] X.H. Chen, F.F. Ren, S.L. Gu, “Review of gallium-oxide-based solar-blind ultraviolet photodetectors,” Photonics Research, vol. 7, pp. 381-415, Apr. 2019.
[6] Li, Fangzheng; Wang, Lianshan; Zhao, Guijuan; Meng, Yulin; Li, Huijie; Chen, Yanan; Yang, Shaoyan; Jin, Peng; Wang, Zhanguo “The Residual Stress and Al Incorporation of AlGaN Epilayers by Metalorganic Chemical Vapor Deposition” Journal of Nanoscience and Nanotechnology, Volume 18, Number 11, pp. 7484-7488(5) November 2018.
[7]Shanshan Chen, Xinhua Pan, Chenxiao Xu, Xiangyang Chen, Jingyun Huang, Zhizhen Ye “Epitaxial growth and stress analysis of Zn1-xMgxO films on (111) Si substrates” Thin solid film ,volume628 , pp. 50-5330, April 2017.
[8] B. W. Krueger, C. S. Dandeneau, E. M. Nelson, S. T. Dunham, F. S. Ohuchi, and M. A. Olmstead, “Variation of band gap and lattice parameters of β−(AlxGa1-x)2O3 powder produced by solution combustion synthesis,” J. Am. Ceram. Soc., vol. 99, no. 7, pp. 2467–2473, Jul. 2016.
[9] X. H. Chen, F. F. Ren, S. L. Gu, and J. D. Ye, "Review of gallium-oxide-based solar- blind ultraviolet photodetectors," Photonics Res., Review vol. 7, no. 4, pp. 381-415, doi: 10.1364/prj.7.000381, Apr 2019.
[10] Y. Gu, G. F. Yang, A. Danner, D. W. Yan, N. Y. Lu, X. M. Zhang, F. Xie, Y. K. Wang,B. Hua, X. F. Ni, Q. Fan, X. Gu, and G. Q. Chen, "Analysis of high-temperature carrier transport mechanisms for high Al-content Al0.6Ga0.4N MSM photodetectors," IEEE Trans. Electron Devices, Article vol. 67, no. 1, pp. 160-165, doi: 10.1109/ted.2019.2953881 ,Jan 2020,.
[11] N. Hu, D. Y. Jiang, G. Y. Zhang, Z. X. Guo, W. Zhang, X. J. Yang, S. Gao, T. Zheng, Q.C. Liang, and J. H. Hou, "Voltage controlled dual-wavelength ZnO/Au/MgZnO UV photodetectors," Mater. Res. Bull., Article vol. 103, pp. 294-298, doi: 10.1016/j.materresbull.2018.03.054 ,Jul 2018.
[12] Zhang, F; Saito, K.; Tanaka, T.; Nishio, M.; Arita, M.; Guo, Q, “Wide Bandgap Engineering of (AlGa)2O3 Films” Appl. Phys. Lett. 2014, 105, 162107. doi:10. 1063/1.4900522O, October 2014.
[13] T. Oshima, T. Okuno, and S. Fujita, “Ga2O3 thin film growth on c-plane sapphire substrates by molecular beam epitaxy for deep-ultraviolet photodetectors,” Jpn. J. Appl. Phys., Part 1 46, pp.7217-7210 ,doi:10.1143/ JJAP.46.7217, November 2007

[14] Yuan, S.-H.; Wang, C.-C.; Huang, S.-Y.; Wuu, D.-S. “Improved responsivity drop from 250 to 200 nm in sputtered gallium oxide photodetectors by incorporating trace aluminum,” IEEE Electron Device Lett., volume 39, pp.220–223. doi:10.1109/LED.2017. 2782693,2018
[15]Yaolin Cheng, Chunfu Zhang, Yu Xu, Zhe Li, Dazheng Chen, Weidong Zhu, Qian Feng, Shengrui Xu, Jincheng Zhang, Yue Hao “Heteroepitaxial growth of β-Ga2O3 thin films on c-plane sapphire substrates with β-(AlxGa1-x)2O3 intermediate buffer layer by mist-CVD method” Volume 29, 102766 ,December 2021.
[16] Tianshi Wang, Wei Li, Chaoying Ni, and Anderson Janotti “Band gap and band offset of Ga2O3 and (AlxGa1−x)2O3 alloys” Phys. Rev. Applied 10, 011003 – Published 31 July 2018.
[17] Kentaro Kaneko , Kenta Suzuki , Yoshito Ito , Shizuo Fujita “Growth characteristics of corundum-structured α-(AlxGa1−x)2O3/Ga2O3 heterostructures on sapphire substrates” Journal of Crystal Growth”Volume 436, Pages 150-154,15 February 2016.
[18] Hiroshi Ito, Kentaro Kaneko, and Shizuo Fujita” Growth and Band Gap Control of Corundum-Structured a-(AlGa)2O3 Thin Films on Sapphire by Spray-Assisted Mist Chemical Vapor Deposition” Japanese Journal of Applied Physics 51 (2012) 100207
[19] X. H. Chen, F. F. Ren, S. L. Gu, and J. D. Ye, "Review of gallium-oxide-based solar- blind ultraviolet photodetectors," Photonics Res., Review vol. 7, no. 4, pp. 381-415, doi: 10.1364/prj.7.000381, Apr 2019.
[20] Viezbicke, BD ; Patel, S ; Davis, BE ; Birnie,DP “Evaluation of the Tauc method for optical absorption edge determination: ZnO thin films as a model system” PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS,volume252, no.8,pp.1700-1710,DOI10.1002/pssb.201552007,Aug2015.

[21] Liu, HM ; Wang, P ; Shi, YL “Photocurrent and responsivity of quantum dot infrared photodetectors”, JOURNAL OF INFRARED AND MILLIMETER WAVES, volume 35, no.2, pp.139-142,April 2016.
[22] Qiu, MT ; Jia, ZL ; Yang, MY ; Nishimura, K ; Lin, CT ; Jiang, N; Yuan, QL“High detectivity solar blind photodetector based on mechanical exfoliated hexagonal boron nitride films” NANOTECHNOLOGY, volume 34, no.28, DOI10.1088/1361-6528/acccfd, JUL 9 2023.
[23] Shu-Bai Liu, Shoou-Jinn Chang, Sheng-Po Chang, Chia-Hsun Chen. “An Amorphous (Al0.12Ga0.88)2O3 Deep Ultraviolet Photodetector,” IEEE Photonics Journal,Volume 12, Number 4, August 2020
[24] P. W. Chen, S. Y. Huang, C. C. Wang, S. H. Yuan, and D. S. Wuu, “Influence of oxygen on sputtering of aluminum gallium oxide films for deep-ultraviolet detector applications,” Journal of Alloys and Compounds,Volume 791, Pages 1213-121930 June 2019.
[25] Q. Feng, X. Li, G. Han, L. Huang, F. Li, W. Tang, J. Zhang, and Y. Hao, “(AlGa)2O3 solar-blind photodetectors on sapphire with wider bandgap and improved responsivity,” Opt. Mater. Exp., vol. 7, no. 4, pp. 1240–1248, doi: 10.1364/OME.7.001240, 2017.
[26] A F M Anhar Uddin Bhuiyan; Zixuan Feng; Hsien-Lien Huang; Lingyu Meng; Jinwoo Hwang ; Hongping Zhao “Metalorganic chemical vapor deposition of α-Ga2O3 and α-(AlxGa1−x)2O3 thin films on m-plane sapphire substrates,” APL Materials, volume 9 ,issue 10,October 2021.