(Invited) Band Line-up of High-k Oxides on GaN

We present comprehensive experimental work on TixAl1-xOy (with x = 9%, 16%, 25%, 36%, 100%) and GaxAl1-xOy (x = 5%, 20%, 80% and 95%) fabricated using atomic layer deposition with the aim of achieving favorable band alignment with GaN for device applications. The permittivity, k, has been found to be enhanced from ~10 for 9% Ti to 76 for TiO2, but brings unfavorable band line-up and a small conduction band offset (< 0.1 eV) with GaN for all Ti% studied. On the other hand, GaxAl1-xOy (x = 5%, 20%) films show substantial increase of the band gap from 4.5 eV for Ga2O3 to 5.5 eV for x = 5% Ga and 6.0 eV for x = 20% Ga in mixed oxides and a strong suppression of leakage current in associated metal insulator semiconductor (MIS) capacitors.