Comb-Shaped Emitter Engineered p-NiO/n-ZnGa₂O₄/p-Si Heterojunction Bipolar Transistor for High-Performance Solar-Blind Ultraviolet Photodetection

To meet the growing demand for high-performance solar-blind ultraviolet (UV) photodetectors, the development of innovative device architectures is essential. In this work, we propose a p-NiO/n-ZnGa2O4/p-Si heterojunction bipolar transistor with a unique comb-shaped emitter design for solar-blind UV photodetection. The comb-shaped p-NiO film, serving as the emitter and “grating”, demonstrates periodic and selective transparency to solar-blind UV light, thereby allowing incident photons to effectively reach the base-collector junction. Concurrently, this design facilitates effective hole injection into the base, enabling high responsivity through the transistor’s intrinsic amplification mechanism. Unlike conventional heterojunction devices, the photoresponse of the p-NiO/n-ZnGa2O4/p-Si heterojunction bipolar transistor is observed only under reverse bias conditions. Benefiting from an inherent gain mechanism attributed to its transistor action, the p-NiO/n-ZnGa2O4/p-Si heterojunction bipolar transistor demonstrated a high responsivity of 480.1 A/W at −10 V, yielding an exceptionally high external quantum efficiency of 2.3 × 105%. The dominant noise source of the device at low frequencies is flicker noise. Dynamic performance analysis reveals a fast response with rise and decay times of 16.6 and 41.1 ms, respectively. This work underscores the potential of exploiting transistor amplification as a valuable strategy for developing high-performance solar-blind UV photodetectors.