Indium-tin-oxide metal-insulator-semiconductor GaN ultraviolet photodetectors using liquid-phase-deposition oxide

A low-cost and reliable SiO₂ insulating layer was successfully deposited onto GaN by liquid-phase deposition (LPD) using supersaturated H ₂SiF₆ and H₃BP₃ solutions. The interface-trap density, D_it, was estimated to be 1.2 × 10 ¹² cm^-2 eV^-1 for the as-grown, not annealed LPD-SiO₂ layers. It was found that the leakage current density was 2.06 × 10^-5 A/cm² at a negative bias of 10 V for the as-grown Al/20nm LPD-SiO₂/GaN metal-insulator-semiconductor (MIS) capacitors. It was also found that the LPD-SiO₂ layer could be used to suppress the dark current of nitride-based photodetectors. A large photocurrent to dark-current contrast ratio higher than four orders of magnitude and a maximum responsivity of 0.65 A/W were observed from the fabricated indium-tin-oxide (ITO)/LPD-SiO₂/GaN MIS UV photodetectors. These results could be explained by defect-assisted tunneling.