Mobility enhancement in recessed-gate AlGaN/GaN MOS-HFETs using an AlON gate insulator

Abstract

We demonstrated the advantage of aluminum oxynitride (AlON) gate insulator in enhancing the performance of recessed-gate AlGaN/GaN-based metal-oxide-semiconductor heterojunction field-effect transistors (MOS-HFETs) fabricated with reactive ion etching. The AlON deposition on the recessed-gate structures was found to mitigate the damage of recess etching on the GaN and AlGaN surfaces, enabling a simple gate recess process in the device fabrication. Consequently, a high field-effect mobility of 259 cm2 V-1 s-1, together with normally off operation, was achieved for the recessed-gate AlGaN/GaN MOS-HFETs with the AlON gate insulator. Temperature dependence of the transconductance of the fabricated devices revealed that carrier transport in the channel was mostly dominated by phonon scattering, indicating excellent interface quality between the AlON insulator and the recess-etched AlGaN surfaces.