Solar-blind metal-semiconductor-metal photodetectors based on an exfoliated β-Ga₂O₃ micro-flake

Semiconductor materials ideal for solar-blind photodetectors (PDs) require an ultra-wide and direct bandgap to detect UV-C spectral wavelengths effectively. Using the mechanically exfoliated high-quality β-Ga₂O₃ micro-flakes that have a direct bandgap of ∼4.8 eV, we fabricated solar-blind PDs with a metal-semiconductor-metal (MSM) structure that can reduce the dark current, and then systemically investigated their photoresponse properties. The MSM devices with two Ni/Au Schottky contacts exhibited an extremely low dark current and high sensitivity (ratio of photocurrent to dark current > 10³) in UV-C wavelengths. In addition, they exhibited fast and stable on/off characteristics and high responsivity (1.68 A/W), with a superior rejection ratio when compared with the reported thin-film MSM solar-blind PDs, indicating the high potential of the quasi-two-dimensional β-Ga₂O₃ for optoelectronic applications.