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

A solar-blind photodetector based on beta-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 beta-Ga2O3 film layer. With zero bias, that is, zero power consumption, the photodetector shows a fast photoresponse time (decay time tau(d) = 0.07 s) and the ratio I-photo/I-dark approximate to 20 under 254 nm light illumination with a light intensity of 45 mu W/cm(2). Such behaviors are attributed to the separation of photogenerated electron-hole pairs driven by the built-in electric field in the depletion region of beta-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 mu W/cm(2) of 254 nm light illumination, the photodetector exhibits a responsivity R-lambda of 43.31 A/W and an external quantum efficiency of 2.1 x 10(4) %. The photo-to-electric conversion mechanism in the beta-Ga2O3/NSTO heterojunction photodetector is explained in detail by energy band diagrams. The results strongly suggest that a photodetector based on beta-Ga2O3 thin-film heterojunction structure can be practically used to detect weak solar-blind signals because of its high photoconductive gain.