High sensitive and stable self-powered solar-blind photodetector based on solution-processed all inorganic CuMO2/Ga2O3 pn heterojunction

Solar-blind photodetection systems, which can convert solar-blind deep ultraviolet light into an electrical signal, have been designed for practical use owing to their high sensitivity and accuracy. As one of the most suitable semiconductors for solar-blind photodetection, β-Ga2O3 can construct a pn type photodetector with another semiconductor material to meet the demands of energy savings, miniaturization and high efficiency. As a kind of natural p-type material, delafossite semiconductor materials CuMO2 (M = Al3+, Ga3+, In3+, Cr3+) have attracted much attention recently. The band alignment of CuMO2 is staggered with that of n-type β-Ga2O3; hence, the photogenerated electrons and holes tend to transfer through the interface in the opposite directions, resulting in spatial separation of charge carriers. Meanwhile, the fast hole diffusion coefficient (10−2–101 cm2 V−1 s−1) of CuMO2 guarantees the transport of holes, which is difficult in β-Ga2O3 owing to its intrinsic electronic structure. More importantly, compared with the widely used p-type materials, CuMO2 materials are almost insensitive to UVA light owing to the forbidden intrinsic direct transitions between the conduction and valence bands. Hence, the CuMO2/β-Ga2O3 pn junction photodetector exhibits high sensitivity, and the working spectral region is not extended to the UVA region. In this study, n-β-Ga2O3/p-CuMO2 (M: Ga3+, Cr3+) pn junction photodetectors were prepared by a simple solution process method. Due to the high crystallinity of the as-grown CuGaO2 and CuCrO2, the CuGaO2/β-Ga2O3 and CuCrO2/β-Ga2O3 pn junction photodetectors demonstrate an ultralow off state current of 51/61 fA, a superhigh on-to-off state current ratio of 2.3 × 104/3.5 × 104 and a high rejection ratio (R254/R365) of 2 × 104/2.8 × 104 under a bias of 0 V. The CuMO2/β-Ga2O3 pn junction photodetector satisfies the requirements of high sensitivity, stable and energy saving and has wide practical application prospect in solar-blind detection systems.