Wide bandgap tunable deep ultraviolet Ga2O3/GaN heterojunction photodetector

Gallium oxide (Ga2O3), an ultra-wide bandgap semiconductor (4.5–5.3 eV), offers mature fabrication methods and inherent ultraviolet (UV) filtering, making it ideal for solar-blind UV photodetectors (PDs). This study presents Ga2O3/GaN heterojunction PDs fabricated through high-temperature thermal oxidation at different durations (45 min and 8 h) to control film thickness. Metal–semiconductor–metal structures with 2 μm interdigitated electrodes were employed to enhance detection performance. Device 2, produced with an 8-h oxidation, shows stable solar-blind UV detection (200–280 nm) across a 3–20 V bias range. In contrast, device 1, with a 45-min oxidation, demonstrates bias-dependent tunability. At lower voltages (3–5 V), it exhibits enhanced solar-blind photocurrent due to the extension of the depletion region into the GaN layer. This design benefits from a small conduction band offset (∼0.1 eV), facilitating electron transport, and a large valence band offset (∼1.4 eV), which restricts hole movement, resulting in strong photoconductive gain. At 10 and 15 V, device 1 transitions to a full UV response (270–370 nm) with a responsivity of up to 24 A/W. At 20 V, it shifts to a near-UV detection range (320–380 nm), achieving a peak responsivity of 40 A/W. These findings highlight that thermal oxidation duration and bias control enable wavelength-tunable UV detection. The approach provides a scalable, cost-effective method for designing high-performance, multi-mode Ga2O3/GaN UV photodetectors suitable for solar-blind applications.