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

Sc 2 O 3 is a promising gate dielectric for surface passivation in GaN-based devices. However, the interface quality and band alignment of sputtered Sc 2 O 3 on GaN has not been fully explored. In this work, x-ray photoelectron spectroscopy (XPS) and variable angle spectroscopic ellipsometry were performed to extract the discontinuities in the valence and conduction bands of the Sc 2 O 3 /GaN system. Sc 2 O 3 films were deposited on GaN using radio frequency sputtering. The valence band offset of Sc 2 O 3 /GaN was determined to be 0.76 ± 0.1 eV using Kraut’s method. The Sc 2 O 3 band gap of 6.03 ± 0.25 eV was measured using O 1s energy loss spectroscopy. The electron affinity measurements of GaN and Sc 2 O 3 using XPS secondary electron cut-off spectra provided an additional degree of accuracy to the derived band line-up for the Sc 2 O 3 /GaN interface. The band alignment results were compared with literature values of band offsets determined experimentally and theoretically for differently grown Sc 2 O 3 films on GaN.