Evaluation and mitigation of reactive ion etching-induced damage in AlGaN/GaN MOS structures fabricated by low-power inductively coupled plasma

Abstract

AlGaN/GaN metal-oxide-semiconductor (MOS) structures were fabricated by low-power inductively coupled plasma reactive ion etching (ICP-RIE) and chemical vapor deposition of SiO2 dielectrics on the etched surfaces, and they were systematically investigated by physical and electrical characterizations in an effort to develop a low-damage recessed gate process. Although ICP-RIE with reduced bias power was able to suppress nitrogen deficiencies and native oxide growth on damaged AlGaN surfaces, compositional changes due to selective aluminum removal were found to be inevitable. On the other hand, thin damaged layers were completely oxidized to form GaOx interface layers at the initial stage of SiO2 deposition, leading to dielectric/etched-AlGaN interfaces with excellent electrical properties. Furthermore, Hall-effect measurements showed negligible impact on the two-dimensional electron gas beneath the AlGaN layers etched under very low bias conditions. The current comprehensive research demonstrates the significant advantages of the proposed low-damage recessed gate process for fabricating next-generation AlGaN/GaN MOS-HFET devices.