Band Line-up Investigation of Atomic Layer Deposited TiAlO and GaAlO on GaN

A comprehensive study of the band alignments of TixAl1-xOy(with x = 9%, 16%, 25%, 36%, 100%) and GaxAl1-xOy(x = 5%, 20%, 80% and 95%) fabricated using atomic layer deposition on GaN has been presented using X-ray photoelectron spectroscopy and variable angle spectroscopic ellipsometry. The permittivity, k, has been found to be enhanced from similar to 10 for 9% Ti in Ti(x)Al(1-x)O(y)to 76 for TiO2, however TiO(2)brings an unfavorable band alignment and a small conduction band offset (<0.1 eV) with GaN. The latter has been observed for all studied Ti(x)Al(1-x)O(y)films deposited on GaN. On the other hand, Ga(x)Al(1-x)O(y)films show a substantial increase of the band gap from 4.5 eV for Ga(2)O(3)to 5.5 eV for x = 20% Ga and 6.0 eV for x = 5% Ga. A strong suppression of leakage current in associated GaxAl1-xOy-based metal insulator semiconductor capacitors has also been observed, showing promise for device applications.