GaN and AlGaN high-voltage rectifiers grown by metal-organic chemical-vapor deposition

Abstract

In this paper, we report the study of the electrical characteristics of GaN and AlGaN vertical p-i-n junctions and Schottky rectifiers grown on both sapphire and SiC substrates by metal-organic chemical-vapor deposition. For GaN p-in rectifiers grown on SiC with a relatively thin "i" region of 2 µm, a breakdown voltage over 400 V, and forward voltage as low as 4.5 V at 100 A/cm2 are exhibited for a 60µm-diameter device. A GaN Schottky diode with a 2-µm-thick undoped layer exhibits a blocking voltage in excess of ˜230 V at a reverse-leakage current density below 1 mA/cm2, and a forward-voltage drop of 3.5 V at a current density of 100 A/cm2. It has been found that with the same device structure and process approach, the leakage current of a device grown on a SiC substrate is much lower than a device grown on a sapphire substrate. The use of Mg ion implantation for p-guard rings as planar-edge terminations in mesageometry GaN Schottky rectifiers has also been studied.