Barrier-height-enhanced n-GaN Schottky photodiodes using a thin p-GaN surface layer

A p+-GaN surface layer of 15 nm was incorporated in n-GaN Schottky photodiode to enhance the effective Schottky barrier height. A barrier height of 1.09eV for the normal n-GaN Schottky photodiode was increased to the effective barrier height of 1.16eV. The resulting photodiodes show a reverse dark current density of as low as 4.8 × 10^-10 A/cm² at -2V bias, which is about three orders of magnitude lower than that of the normal n-GaN Schottky photodiode. The lower dark current leads to a significant improvement in the visible rejection ratio. A peak responsivity of 107 mA/W was obtained at -2 V bias under the incident power density of 10μ,W/cm², corresponding to an external quantum efficiency of 38%.