Ultrahigh-Performance Photovoltaic Ga₂O₃ Solar-Blind Ultraviolet Detectors via Two-Dimensional Step-Flow Growth and Drift Region Optimization

Photovoltaic solar-blind ultraviolet photodetectors (SBPDs) operate independently of an external power source, addressing critical demands in extreme environments, such as forest fire detection and atmospheric ozone layer monitoring. Gallium oxide (Ga₂O₃) offers significant potential for extreme applications due to its radiation resistance and high-temperature stability. Here, we present a novel homoepitaxy strategy to produce an "atomic smooth" step-flow Ga₂O₃ photosensitive layer, successfully fabricating device-grade Ga₂O₃/n⁺-Ga₂O₃ homojunctions for photovoltaic SBPDs. These devices exhibit a maximum open-circuit voltage of 1.0 V, an ultrahigh external quantum efficiency of 59.5%, and an ultrafast response time of 100 ns under zero bias, maintaining consistent performance even at 390 K. By implementing a 2D step-flow growth mode, both bulk and interface defects were effectively suppressed, achieving the desired band alignment. Furthermore, the optimized high-quality depletion region formed by the Ga₂O₃ layer facilitates enhanced carrier drift, resulting in an efficient carrier collection. This work fully explores the potential of Ga₂O₃ SBPDs for extreme applications and provides an effective design strategy for achieving photovoltaic detectors characterized by zero power consumption, high responsivity, and rapid response.