Nitride-Based UV Metal–Insulator–Semiconductor Photodetector with Liquid-Phase-Deposition Oxide

Abstract

A low-temperature (30–40°C), low-cost and reliable method of liquid phase deposition (LPD) has been employed to grow SiO2 layers on GaN. The LPD process uses a supersaturated acid aqueous solution of hydrofluosilicic (H2SiF6) as a source liquid and an aqueous solution of boric acid (H3BO3) as a deposition rate controller. In this study, the LPD SiO2 was prepared at 40°C with concentrations of H2SiF6 and H3BO3 at 0.2 and 0.01 M, respectively. The minimum interface-trap density, Dit, of a metal–insulator–semiconductor (MIS) capacitor with a structure of Al/20 nm LPD-SiO2/n-GaN was estimated to be 8.4×1011 cm-2 V-1. Furthermore, a MIS photodetector with a 10-nm-thick LPD-SiO2 layer has been fabricated successfully. The dark current density was as low as 4.41×10-6 A/cm2 for an applied field of 4 MV/cm. A maximum responsivity of 0.112 A/W was observed for incident ultraviolet light of 366 nm with an intensity of 4.15 mW/cm2. Defect-assisted tunneling was invoked to explain these results.