High-Speed and Ultrasensitive Solar-Blind Ultraviolet Photodetectors Based on In Situ Grown β-Ga 2 O 3 Single-Crystal Films.

Deep-level defects in β-Ga 2 O 3 that worsen the response speed and dark current ( I d ) of photodetectors (PDs) have been a long-standing issue for its application. Herein, an in situ grown single-crystal Ga 2 O 3 nanoparticle seed layer (NPSL) was used to shorten the response time and reduce the I d of metal-semiconductor-metal (MSM) PDs. With the NPSL, the I d was reduced by 4 magnitudes from 0.389 μA to 81.03 pA, and the decay time (τ d1 /τ d2 ) decreased from 258/1690 to 62/142 μs at -5 V. In addition, the PDs with the NPSL also exhibit a high responsivity (43.5 A W -1 ), high specific detectivity (2.81 × 10 14 Jones), and large linear dynamic range (61 dB) under 254 nm illumination. The mechanism behind the performance improvement can be attributed to the suppression of the deep-level defects (i.e., self-trapped holes) and increase of the Schottky barrier. The barrier height extracted is increased by 0.18 eV compared with the case without the NPSL. Our work contributes to understanding the relationship between defects and the performance of PDs based on heteroepitaxial β-Ga 2 O 3 thin films and provides an important reference for the development of high-speed and ultrasensitive deep ultraviolet PDs.