Electronic states of plasma-enhanced atomic layer deposited SiO2 on GaN

Silicon dioxide is a stable dielectric with a large bandgap that leads to effective band offsets suitable for wide bandgap semiconductor electronics. This research is focused on band offsets and bending for plasma-enhanced atomic layer deposited (PEALD) SiO2 on GaN. We have thus investigated SiO2 using tris(dimethylamino)silane (TDMAS) and oxygen plasma on GaN substrates. Film thicknesses, compositions, and band offsets were determined with \textit{in-situ} x-ray photoelectron spectroscopy (XPS). Results showed the growth rate for TDMAS and oxygen plasma process increased as temperature decreased within the ALD regime. The growth rate was higher at 550\textdegree C, which was likely the result of thermal decomposition of TDMAS. Results demonstrated temperature does not greatly affect the stoichiometry of the films. A more detailed analysis showed increasing deposition temperature resulted in a secondary O1s peak; however, this peak was not present for thick films. This secondary peak likely suggests high temperatures relate to the oxidization of the GaN substrates. This effect may also explain the variation in observed valence band offsets (VBO), where the measurement technique does not account for the potential drop across an interfacial Ga-O layer.