Three Orders of Reverse Leakage Reduction by Using Supercritical CO2 Nitriding Process on GaN Quasi-Vertical Schottky Barrier Diode

Surface treatment is quite vital to reduce the reverse leakage current and improve the current On–Off ratio of gallium nitride (GaN) quasi-vertical Schottky barrier diode (SBD). In this work, we report a new nondestructive low temperature supercritical CO2 fluid (SCF) nitridation technology to treat the surface of GaN and substantially reduce the leakage current of GaN quasi-vertical SBD. The X-ray photoelectron spectroscopy (XPS) reveals the increased nitriding degree and oxygen doping degree in the form of GaO x after the SCF process results in the leakage performance improvement. As a result, the defects at metal/semiconductor interface are passivated. Also, because of NH-2 and OH− generated from the SCF process, the surface peak electric field of n−GaN decreases, and thus the breakdown voltage is enhanced. The reverse leakage current density is reduced by more than three orders of magnitude from $3.7\times 10^{-{6}}$ to $3.52\times 10^{-{9}}$ A/cm2 (at −3 V) and the ON-/ OFF-current ratio is improved by three orders from $8\times 10^{{7}}$ to $5.74\times 10^{{10}}$ .