Indium–Tin-Oxide Metal–Insulator–Semiconductor GaN Ultraviolet Photodetectors Using Liquid-Phase-Deposition Oxide

A low-cost and reliable SiO 2 insulating layer was successfully deposited onto GaN by liquid-phase deposition (LPD) using supersaturated H 2 SiF 6 and H 3 BO 3 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-SiO 2 layers. It was found that the leakage current density was 2.06 × 10 -5 A/cm 2 at a negative bias of 10 V for the as-grown Al/20 nm LPD-SiO 2 /GaN metal–insulator–semiconductor (MIS) capacitors. It was also found that the LPD-SiO 2 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-SiO 2 /GaN MIS UV photodetectors. These results could be explained by defect-assisted tunneling.