【Member News】A New Breakthrough has been Made in the Research of Gallium Oxide Innovation Center of Nanjing University of Posts and Telecommunications (IC-GAO)

      At present, great progress has been made in ultraviolet light detection technology based on wide band gap semiconductor. Due to its characteristics and photoresponse, large-scale, high performance photodetector unit array is widely used in image sensing, environmental monitoring, biological research and space exploration and other fields, promoting the development of modern optoelectronic devices. Gallium oxide (Ga₂O₃) is the representative wide band gap semiconductor, and its direct band gap of ~ 4.9 eV can be used to detect solar-blind ultraviolet irradiation. Currently, the Ga₂O₃-based photodetector array lacks a certain number of units despite its considerable photoresponse performance. Professor Tang Weihua's team first reported the Ga₂O₃ rectangular array of unit 16 in 2018 [IEEE Photon. Technol. Lett., 2018,30,993], and in 2021 they reported the Ga₂O₃ linear array of Unit 64 [IEEE Trans. Electron Devices, 2021,68,3435]; The Ga₂O₃ array detectors and imaging applications of different sizes were also reported by Zhengzhou University, University of Science and Technology of China, Hefei University of Technology and Indian scholars in succession. However, the current designed array still has many disadvantages, such as the small number of detector array units, single array structure, large unit area resulting in low crystal utilization rate, poor micromachining technology and immature patterned growth technology. To achieve better performance, such as obtaining high-resolution sensing images, more array units need to be integrated on a single chip. The basic problems to be solved at present lie in the large area uniformity of the film and the reasonable design of the array wiring.

Graphical representation of the gallium oxide array detector development process

      Recently, thanks to years of accumulation in Ga₂O₃-based photoconductivity, Schott-based type and heterostructure photodetectors, the Gallium Oxide Innovation Center (IC-GAO) led by Professor Tang Weihua of Nanjing University of Posts and Telecommunications has successfully prepared solar-blind UV detector based on 2-inchβ-Ga₂O₃ films with array of 8x8 and 16x16 by MOCVD growth. Compared with the linear layout, the 16x16 square layout in this work is more conducive to saving the occupied area of the detector array, facilitating integrated applications, and requires no complex insulation and isolation process. Complex images can be recorded and read out quickly at the same time through the external circuit. The UV / vis inhibition ratio of this 8x10³ array showed excellent wavelength selectivity, laying the basis for accurate solar-blind UV imaging. The response degree reached 60.7 A W^-1, detection degree 2.2x10¹⁴ Jones, 120.34 dB in linear dynamic zone, and fast response time. Notably, electrical testing of 256 units revealed a dark current all between 2 pA and 4 pA, with a maximum standard deviation of 6% -10%. These data demonstrate the good uniformity of the device and the potential in the field of UV image sensing applications. The results were published in IEEE Electron Device Letters (doi: 10.1109/LED.2023.3272909) and Science China Technological Sciences (doi: 10.1007/s11431-022-2404-8). The first author of the thesis is graduate student Shen Gaohui, and the corresponding authors are Professor Tang Weihua and Associate Professor Liu Zeng. The work was completed in close cooperation with Professor Guo Yufeng's team, and the research was funded by the National Key Research and Development Program and the National Natural Science Foundation of China and other projects.

Detector Array and Imaging Applications Based on 2-inch β-Ga2O3 Films

      Professor Tang Weihua's team has been focusing on gallium oxide research for more than ten years, They are the first pioneers of Ga₂O₃ scientific research and industrialization practice in China. They have made a number of important breakthroughs and progress in the fields of material growth (single crystal / epitaxy), crystal phase / physical property regulation, surface interface / energy band engineering, gold-semi contact, photoelectric and information memory device structure design and construction, and has been formed a distinctive independent innovation system in this research field. Based on the research experience of Ga₂O₃ epitaxial film and solar blind detector, a thesis which is titled  "Basic Research on Gallium Oxide Epitaxial Eilm and Deep Ultraviolet Sensor Parts" won the second prize of Beijing Natural Science in 2020. The team was judged the most active research team in the field by the Air Force Research Laboratory. Under the severe situation of export control on ultra-wide band gap semiconductor materials such as Ga₂O₃ the United States and other Western countries, the team's research in β-Ga₂O₃ single crystal growth and substrate processing technology has provided a convenient material basis for device research and development.

Paper Link：

1. 16×16 Solar-Blind UV Detector Based on β-Ga₂O₃ Sensors, IEEE Electron Device Lett., https://ieeexplore.ieee.org/document/10115448
2. High responsivity and fast response 8×8 β-Ga₂O₃ solar-blind ultraviolet imaging photodetector array, Sci. China Technol. Sci.,http://engine.scichina.com/doi/10.1007/s11431-022-2404-8
3. 16×4 Linear Solar-Blind UV Photoconductive Detector Array Based on β-Ga₂O₃ Film, IEEE Trans. Electron Devices, https://ieeexplore.ieee.org/document/9443644
4. Arrays of Solar-Blind Ultraviolet Photodetector Based on β-Ga₂O₃ Epitaxial Thin Films, IEEE Photonics Technol. Lett., https://ieeexplore.ieee.org/document/8337767