Ultralow dark current and high specific detectivity of Ga2O3-based solar-blind photodetector arrays realized via post-annealing in oxygen plasma

Ga2O3 has an ultra-wide bandgap of 4.9 eV and is a suitable semiconductor for solar-blind photodetectors (SBPDs). However, the present study shows that the dark current of the Ga2O3-based SBPDs is high due to the defects on the surface and inside the crystal, and the specific detectivity of the devices is also limited to some extent. In this work, we combine post-annealing with plasma treatment, proposing a method for plasma treatment at a high temperature, which yields outstanding device performance. It is demonstrated that the SBPD based on Ga2O3 thin films treated with oxygen plasma at 700 degrees C possesses excellent overall performance, including an ultralow dark current of 44 fA, a high specific detectivity of 1.45 x 1016 Jones, a decay time of 58 ms and a responsivity of 264.1 A W-1 at a bias of 20 V. Furthermore, we fabricate a 10 x 10 photodetector array based on 1-inch Ga2O3 thin films treated with oxygen plasma at 700 degrees C, with excellent uniformity of photocurrent and dark current distribution across all pixels as well as an excellent imaging capability. Finally, in combination with the analysis of photoluminescence spectra and valence band spectra, the underlying physical mechanism based on the energy band diagram has been proposed to interpret the obtained experimental result. This work has advanced the development of high-performance Ga2O3-based SBPDs and promoted their application in high-precision solar-blind ultraviolet imaging.