Investigating the effect of O 2 plasma treatment on the operational characteristics of Schottky-gate AlGaN/GaN HEMT

This study investigates the effect of O 2 plasma treatment on the physical and electrical properties of the surface region in Schottky-gate AlGaN/GaN high electron mobility transistor (HEMT). We demonstrate that O 2 plasma treatment significantly reduces the gate leakage current and enhances the on/off ratio by three orders of magnitude compared to devices without treatment. The O 2 plasma treatment removes organic chemical residue and forms Ga–O bonds on the AlGaN surface beneath the gate metal. X-ray photoelectron spectroscopy results indicate that the treatment effectively forms a Ga–O compound oxide layer, which provides surface passivation. Furthermore, atomic force microscope analysis reveals a 50% reduction in surface roughness after the O 2 plasma treatment. Using O 2 plasma oxidation treatment caused a shift in the threshold voltage ( V TH ) of Schottky-gate AlGaN/GaN HEMT. Initially measured at −5.26 V, the V TH value shifted to +0.5 V. Furthermore, we also employ TCAD simulation to assist in the process developed during the manufacturing process. It is worth noting that the drain current decreases as the Ga–O compound oxide layer increases. This is due to effectively depleted the polarization charges at the AlGaN/GaN interfaces during E-mode operation when reducing the thickness of the AlGaN layer beneath the gate metal. Our results demonstrate the importance of O 2 plasma surface treatment in achieving optimal device performance. This study systematically discusses the effect of O 2 plasma on AlGaN/GaN surface properties and the formation of Ga–O bonding. It offers insights into developing high-performance Schottky-gate AlGaN/GaN HEMT.