High sensitivity, high solar rejection ratio, and fast response are essential characteristics for most practical applications of solar-blind ultraviolet (UV) detectors. These features, however, usually require a complex device structure, complicated process, and high operating voltage. Herein, a simply structured n-AlGaN/AlN phototransistor with a self-depleted full channel is reported. The self-depletion of the highly conductive n-AlGaN channel is achieved by exploiting the strong polarization-induced electric field therein to act as a virtual photogate. The resulting two-terminal detectors with interdigital Ohmic electrodes exhibit an ultrahigh gain of 1.3×105, an ultrafast response speed with rise/decay times of 537.5 ps/3.1 μs, and an ultrahigh Johnson and shot noise (flicker noise) limited specific detectivity of 1.5×1018 (4.7×1016) Jones at 20-V bias. Also, a very low dark current of the order of ～pA and a photo-to-dark current ratio of above 108 are obtained, due to the complete depletion of the n-Al0.5Ga0.5N channel layer and the high optical gain. The proposed planar phototransistor combines fabrication simplicity and performance advantages, and thus is promising in a variety of UV detection applications.

Jiabing Lu;Zesheng Lv;Xinjia Qiu;Shiquan Lai;Hao Jiang

School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510006, China;State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510006, China;Guangdong Engineering Technology R & D Center of Compound Semiconductors and Devices, Sun Yat-sen University, Guangzhou 510006, China

光子学研究（英文）

[1]Jiabing Lu;Zesheng Lv;Xinjia Qiu;Shiquan Lai;Hao Jiang-.Ultrasensitive and high-speed AlGaN/AlN solar-blind ultraviolet photodetector: a full-channel-self-depleted phototransistor by a virtual photogate)[J].光子学研究（英文）,2022(09):2229

photogate,5Ga0

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