The effect of the dielectric SiO2 layer on the characteristics of visible-blind ultraviolet photodetectors based on ultrathin GaN epitaxial layers grown on c-Al2O3 substrates

In this work ultraviolet metal-semiconductor-metal and metal-insulator-semiconductor photodetectors based on GaN epitaxial layers were fabricated. N-polar GaN epitaxial layers were synthesized by plasma-assisted molecular beam epitaxy on nitrided sapphire substrates. To form Schottky barrier contacts a Ni/Au metallization was chosen. SiO₂ layers were deposited by plasma enhanced chemical vapor deposition. I-V characteristics of fabricated photodetectors were studied. It was found that the dark current of the photodetectors decreased by 49 times after introducing a 20 nm thick SiO₂ dielectric layer, and the photocurrent to dark current ratio increased by a maximum of 35 times.