Zero-Power-Consumption Solar-Blind Photodetector Based on β-Ga₂O₃/NSTO Heterojunction

A solar-blind photodetector based on β-Ga₂O₃/NSTO (NSTO = Nb:SrTiO₃) heterojunctions were fabricated for the first time, and its photoelectric properties were investigated. The device presents a typical positive rectification in the dark, while under 254 nm UV light illumination, it shows a negative rectification, which might be caused by the generation of photoinduced electron-hole pairs in the β-Ga₂O₃ film layer. With zero bias, that is, zero power consumption, the photodetector shows a fast photoresponse time (decay time τ_d = 0.07 s) and the ratio I_photo/I_dark ≈ 20 under 254 nm light illumination with a light intensity of 45 μW/cm². Such behaviors are attributed to the separation of photogenerated electron-hole pairs driven by the built-in electric field in the depletion region of β-Ga₂O₃ and the NSTO interface, and the subsequent transport toward corresponding electrodes. The photocurrent increases linearly with increasing the light intensity and applied bias, while the response time decreases with the increase of the light intensity. Under -10 V bias and 45 μW/cm² of 254 nm light illumination, the photodetector exhibits a responsivity R_λ of 43.31 A/W and an external quantum efficiency of 2.1 × 10⁴ %. The photo-to-electric conversion mechanism in the β-Ga₂O₃/NSTO heterojunction photodetector is explained in detail by energy band diagrams. The results strongly suggest that a photodetector based on β-Ga₂O₃ thin-film heterojunction structure can be practically used to detect weak solar-blind signals because of its high photoconductive gain.