High-performance normally-off Si-doped β-Ga2O3 deep ultraviolet phototransistor grown on N-doped β-Ga2O3

• A transistor-type photodetector (PD) can control the channel current. • Normally-off transistor-type PDs have advantages such as low leakage current. • Ga 2 O 3 N-doping enhances insulation and enables precise control of channel thickness. • It exhibits stable and fast switching characteristics under pulsed bias voltage. • The shortest rise and decay times of 3.8 ms and 3.5 ms, respectively, achieved. β -phase gallium oxide (β-Ga 2 O 3 ) is attracting attention as a deep—ultraviolet photodetector (PD) owing to its large band gap of 4.9 eV, almost direct band gap characteristics, and solar-blind photodetection. However, most Ga 2 O 3 -based transistor-type PDs operate in a normally-on mode. In this study, a silicon (Si)-doped β -Ga 2 O 3 epilayer with normally-off characteristics was grown on a nitrogen (N)-doped buffer layer of a c -plane Al 2 O 3 substrate using metal–organic chemical vapor deposition. The N-doped layer acts as a buffer layer during Si-doped β -Ga 2 O 3 growth and improves crystallinity. In addition, the N-doped buffer layer has semi-insulating properties that reduce leakage current, enabling precise control of the effective thickness of the Si-doped β -Ga 2 O 3 epilayer. Phototransistors are fabricated to improve the characteristics of ultraviolet PDs, such as photo-to-dark current ratio and on–off time. The Si-doped β -Ga 2 O 3 -based transistor-type PD has a detectivity of 3.85 × 10 16 Jones at a wavelength of 260 nm. It achieves detectivity values similar to those of flake-based PDs, and performs the best amongst non-flake-based PDs. Moreover, its rising time and decay time are 3.8 ms and 3.5 ms, respectively; these are among the smallest values reported for existing Ga 2 O 3 -based transistor-type PDs. The fabricated epilayer will facilitate the fabrication of high-performance and efficient photo-electronic devices.