Effect of Thermal Cleaning Prior to p-GaN Gate Regrowth for Normally Off High-Electron-Mobility Transistors

Abstract

This work studied the effect of thermal cleaning in metal–organic chemical vapor deposition (MOCVD) prior to p-GaN gate regrowth for normally off high-electron-mobility transistors. X-ray photoelectron spectroscopy, capacitance–voltage measurement, and atomic force microscopy were employed to identify the effects of thermal cleaning before p-GaN regrowth. It was found that the residual damage was hardly repaired at a relatively low thermal cleaning temperature, while GaN decomposition would occur at an excessively high temperature. Thermal cleaning at 850 °C for 2 min in MOCVD can effectively remove the surface contamination and alleviate the etch damage without causing any significant deterioration of the AlGaN barrier. In addition, the density of interface states (Dit) in the p-GaN gate was reduced from 1012–1013 to 1011–1012 eV–1·cm–2, resulting in a low gate reverse leakage of 0.1 nA/mm @ VDS-OFF = 180 V, a high Ion/Ioff ratio of 4 × 1010, and a relatively high threshold voltage of +1.7 V @ ID = 10 μA/mm.