Ultrahigh-Responsivity, Rapid-Recovery, Solar-Blind Photodetector Based on Highly Nonstoichiometric Amorphous Gallium Oxide

Abstract

Recently, Ga 2 O 3 -based, solar-blind photodetectors (PDs) have been extensively studied for various commercial and military applications. However, to date, studies have focused only on the crystalline phases, especially β-Ga 2 O 3, and the crystalline quality must be carefully controlled because of its strong impact on device characteristics. Based on previous reports, amorphous-semiconductor-based PDs can also be expected to exhibit excellent photodetection characteristics. In this work, amorphous gallium oxide thin films were deposited by radio frequency (RF) magnetron sputtering, and the metal–semiconductor–metal (MSM) PD was fabricated and compared with a β-Ga 2 O 3 film prepared side-by-side as the control sample. The as-sputtered film possessed a high density of defects, including structural disorders, oxygen vacancies, and likely, dangling bonds, resulting in record-high responsivity (70.26 A/W) for a thin-film-type gallium oxide PD due to a high internal gain and the contribution of extrinsic transitions despite a relatively large dark current. The high sensitivity was further confirmed by a high 250 nm/350 nm rejection ratio exceeding 10 5, the specific detectivity as large as 1.26 × 10 14 Jones, and a cutoff wavelength of 265.5 nm. A rapid recovery (0.10 s) rather than a strong, persistent photoconductivity was observed and attributed to effective surface recombination. Our findings contribute to a more comprehensive understanding of highly nonstoichiometric amorphous gallium oxide thin films and reveal additional pathways for the development of high-performance, solar-blind PDs that are inexpensive, large-area, and suitable for mass production.