Effects of Post Annealing on Electrical Performance of Polycrystalline Ga2O3 Photodetector on Sapphire

Effects of post annealing on the physical and electrical properties of solar-blind polycrystalline gallium oxide (Ga 2 O 3 ) ultraviolet photodetectors on the sapphire substrate are investigated. The grain size of poly-Ga 2 O 3 becomes larger with the post annealing temperature (PAT) increasing from 800 °C to 1000 °C, but it gets smaller with further raising PAT to 1100 °C. A blue shift is observed at the absorption edge of the transmittance spectra of Ga 2 O 3 on sapphire as increasing PAT, due to the incorporation of Al from the sapphire substrate into Ga 2 O 3 to form (Al x Ga 1– x ) 2 O 3 . The high-resolution X-ray diffraction and transmittance spectra measurement indicate that the substitutional Al composition and bandgap of (Al x Ga 1– x ) 2 O 3 annealed at 1100 °C can be above 0.30 and 5.10 eV, respectively. The R max of the sample annealed at 1000 °C increases about 500% compared to the as-deposited device, and the sample annealed at 1000 °C has short rise time and decay time of 0.148 s and 0.067 s, respectively. This work may pave a way for the fabrication of poly-Ga 2 O 3 ultraviolet photodetector and find a method to improve responsivity and speed of response.