Self-Powered Vertical Schottky Junction Solar-Blind Photodetector Constructed by Direct MOCVD Epitaxy ZnGa₂O₄ on Platinum

In this study, a Pt/ZnGa2O4/ITO vertical Schottky solar-blind photodetector was successfully accomplished by direct epitaxy high-quality ZnGa2O4 thin film on the sputtered Pt metal film for the first time. It is clearly observed that ZnGa2O4 film on Pt exhibited a narrow full width of half maxima of ~0.69° of X-ray diffraction peak, indicating excellent crystallinity. The Pt/ZnGa2O4/ITO vertical Schottky device shows giant rectification with a rectification ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 1.8\times 10^{{5}}$ </tex-math></inline-formula> at ±5 V bias. Moreover, a relatively high responsivity of 2.44 mA/W at 255 nm, a large UV-Vis rejection ratio of approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.1\times 10^{{3}}$ </tex-math></inline-formula>, and a high −3 dB cut-off frequency of 3 kHz has been clearly achieved at 0 V bias. Additional investigation reveals that high crystal quality of ZnGa2O4 photosensitive layer, relatively high transmittance of ITO top electrode and high reflectivity of Pt Schottky electrode are the key factors to obtain excellent solar-blind UV photodetection performance. This work presents a straightforward method to fabricate a vertical Schottky photodiode, which has great potential applications in miniaturized and integrated self-driven photodetection.