Ultraviolet Photoresponse and Electroluminescence of Exfoliated Ga₂O₃ Flake on p-type GaN

β -phase Ga 2 O 3 ( β -Ga 2 O 3 ) is a promising candidate for deep ultraviolet (UV) solar-blind photodetector due to its large bandgap of 4.9 eV. A high crystal quality two-dimensional β -Ga 2 O 3 flake on p-type GaN ( p -GaN) surface was formed using a facile mechanical exfoliation and transfer method, and the heterojunction photodiode consisting of an n-type β -Ga 2 O 3 flake on a p-type GaN substrate was fabricated. The device exhibited a distinctive rectifying current-voltage (I-V) characteristics with a rectification ratio of 4.0 × 10 5 at ±2 V. The photodetector responded to both 365 nm and 254 nm UV light irradiation with a photocurrent to dark current ratio of 5.64 × 10⁵% for 365 nm and 3.38 × 10⁵% for 254 nm UV. The rise and decay time constants for 365 nm and 254 nm deep UV exposure were obtained through dynamic time-dependent photocurrent measurements. In addition, electroluminescence of the p-type GaN/n-type Ga 2 O 3 heterojunction diode was observed under high forward bias condition.