Improved device performance of recessed-gate AlGaN/GaN HEMTs by using in-situ N2O radical treatment

Abstract

The N2O radicals in-situ treatment on gate region has been employed to improve device performance of recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs). The samples after gate recess etching were treated by N2O radicals without physical bombardment. After in-situ treatment (IST) processing, the gate leakage currents decreased by more than one order of magnitude compared to the sample without IST. The fabricated HEMTs with the IST process show a low reverse gate current of 10−9 A/mm, high on/off current ratio of 108, and high f T × L g of 13.44 GHz⋅μm. A transmission electron microscope (TEM) imaging illustrates an oxide layer with a thickness of 1.8 nm exists at the AlGaN surface. X-ray photoelectron spectroscopy (XPS) measurement shows that the content of the Al–O and Ga–O bonds elevated after IST, indicating that the Al–N and Ga–N bonds on the AlGaN surface were broken and meanwhile the Al–O and Ga–O bonds formed. The oxide formed by a chemical reaction between radicals and the surface of the AlGaN barrier layer is responsible for improved device characteristics.