1D Core@Dual‐Shell Radial Heterojunction for Unipolar Barrier Solar‐Blind Avalanche Photodetector

Abstract Ga₂O₃ based solar‐blind avalanche photodetectors (APDs) are promising for week photodetection in both civil and military applications due to low‐voltage operation, compact dimensions, and optical filter‐free. However, the performance is impeded by low surface‐to‐volume ratio, low barrier height, and elevated dark current. Herein, a 1D ZnO/HfO₂/Ga₂O₃ core@dual‐shell radial heterostructure is designed for high‐performance solar‐blind APDs. A single‐crystal ZnO microwire with smooth surface serves as core framework for shell growth with small lattice mismatch. By incorporating an HfO₂ barrier layer, the conduction band offset is further increased to 2.15 eV without introducing a valence band barrier that would impede hole transport, forming a unipolar barrier structure. This high unipolar barrier suppresses dark current effectively, increases the avalanche breakdown electric field, and enhances the avalanche gain. The optimized APD achieves a responsivity of 2.2 × 10⁵ A W⁻¹ and a detectivity of 3.1 × 10¹⁶ Jones, with an avalanche gain of 4.7 × 10⁴, which is 16 times higher than the HfO₂‐free barrier layer‐modified device. Additionally, it exhibits long‐time stability with a response time of 6.4 ms and a solar‐blind/UVA rejection ratio of 6.25, ensuring immunity to solar interference. This work offers greater design flexibility to develop high‐performance Ga₂O₃‐based APDs and other optoelectronic devices.