Accurate band alignment of sputtered Sc2O3 on GaN for high electron mobility transistor applications

Abstract

Sc2O3 is a promising gate dielectric for surface passivation in GaN-based devices. However, the interface quality and band alignment of sputtered Sc2O3 on GaN is not fully explored. In this work, X-ray photoelectron spectroscopy (XPS) and variable angle spectroscopic ellipsometry (VASE) wereperformed to extract the discontinuities in the valence and conduction band of Sc2O3/GaN system. Sc2O3 films were deposited on GaN using radio frequency sputtering. The valence band offset of Sc2O3/GaN was deterimened to be 0.76±0.1 eV using Kraut's method. The Sc2O3band gap of 6.03± 0.25 eV has been measured using O 1s energy loss spectroscopy. The electron affinity measurements of GaN and Sc2O3 using XPS secondary electron cut-off spectra provide additional degree of accuracy to derived band line-up for Sc2O3/GaN interface. The band alignment results are compared with literature values of bandoffsets determined experimentally and theoretically for differently grown Sc2O3films on GaN.