Band alignment between PEALD-AlNO and AlGaN/GaN determined by angle-resolved X-ray photoelectron spectroscopy

The energy band alignment of AlNO grown by plasma enhanced atomic layer deposited (PEALD) on the AlGaN/GaN heterojunction was analyzed by high resolution angle-resolved X-ray photoelectron spectroscopy (AR-XPS). AlNO was fabricated by alternate growth of AlN and Al2O3 nano-laminations using trimethylaluminum (TMA) and NH3/O2 plasma as precursors in a PEALD chamber. The binding energy (BE) of Ga 3d in AlGaN decreased and the corresponding extracted valence band offset (VBO) increased with increasing take-off angle θ, which indicated upward band bending towards the AlNO/AlGaN interface. The band bending and the potential variation across the AlNO/AlGaN interface were investigated and taken into the calculation for the band alignment. The extracted VBO and conduction band offset (CBO) across the AlNO/AlGaN interface were 1.29 eV and 1.51 eV, respectively, which offered competitive barrier heights (>1 eV) for both electrons and holes. These results indicated AlNO could act as an excellent gate dielectric for AlGaN/GaN high electron mobility transistors (HEMTs).