Enhanced solar-blind photodetection performance of encapsulated Ga<inf>2</inf>O<inf>3</inf> nanocrystals in Al<inf>2</inf>O<inf>3</inf> matrix

Gallium oxide nanocrystals encapsulated in Al2O3 film on a Si substrate have been synthesized by using ion implantation followed by thermal annealing at 800 °C or 900 °C. Formation of β -Ga2O3 nanocrystals is confirmed by transmission electron microscopy. The photoresponse of a photodetector fabricated on the implanted layer by the deposition of interdigitated electrode pattern is estimated by analyzing the current-voltage characteristics. The ratio of photocurrent at the wavelength of 250 nm and a voltage of 4 V to dark current around 15 is found for the sample annealed at 900 °C. The spectral dependence of photoresponse for this sample demonstrates excellent solar-blind ultraviolet characteristics in the wavelength range of 250-270 nm with a rejection ratio 42 at the bias of 1 V. At the bias of 4 V, the responsivity of 50 mA/ μW upon illumination at 250 nm and a cutoff at 280 nm are observed for the 900 °C annealing. The sample annealed at 800 °C shows lower ultraviolet responsivity due to the high density of defects. The data are analyzed in relation to the generation of carriers in Ga2O3 nanocrystals and their transport in the damaged Al2O3 matrix. The reported results pave the way toward the fabrication of next generation high sensitive solar-blind photodetectors.