Self-powered horizontally structured n–n heterojunction photodetector based on Si–GaN/β-Ga₂O₃ for UV detection

With the rapid advancement of optoelectronic technology, high-performance photodetectors are increasingly in demand in fields such as environmental monitoring, optical communication, and defense systems, where ultraviolet detection is critical. However, conventional semiconductor materials suffer from limited UV-visible detection capabilities owing to their narrow bandgaps and high dark currents. To address these challenges, wide-bandgap semiconductors have emerged as promising alternatives. Here, we fabricated a horizontally structured n–n heterojunction photodetector by growing β-Ga₂O₃ on Si–GaN via plasma-enhanced chemical vapor deposition. The device exhibits a self-powered photocurrent of 3.5 nA at zero bias, enabled by the photovoltaic effect of the space charge region. Under 254-nm and 365-nm illumination, it exhibits rectification behavior, achieving a responsivity of 0.475 mA/W (0 V, 220 μW/cm² at 254 nm) and 257.6 mA/W (−5 V), respectively. Notably, the photodetector demonstrates a high photocurrent-to-dark current ratio of 10⁵ under −5-V bias, highlighting its potential for self-powered and high-performance UV detection applications.