Ultrasensitive Deep-Ultraviolet Photodetectors Based On Band Engineering and Ferroelectric Modulation

Wide bandgap semiconductors have emerged as a class of deep-ultraviolet sensitive materials, showing great potentials for next-generation integrated devices. Yet, to achieve a high photoresponse of deep-ultraviolet detector without complicated designs at low supply voltage and weak light intensity is challenging. Herein, a new way is designed to fabricate an ultrasensitive vertical-structured photodetector with epitaxial 7 nm BaTiO₃ interlayer and 10 nm Ga₂O₃ photosensitive layer, realizing the detection to a rare weak deep UV light intensity (0.1 µW cm^{- 2}) at a voltage under 4.8 V and demonstrating a surge in responsivity up to 1.1 A W^-1 with ultrafast response of 0.24 µs/33.4 µs (rise/decay). A responsivity of 3.8 mA W^-1 at 0 V also has been reached. The dark current is suppressed by enlarged conduction band offset and meanwhile the photocurrent is enhanced by unidirectional conducting valance band offset, which formed by BaTiO₃ interlayer. BaTiO₃ also contributes most to the photoresponse at 0 V through its ferroelectric depolarization electric field. These results provide a path toward high-sensitive, low-power-consumption, and highly-integrated deep-ultraviolet detection, beyond conventional ones.