Effect of Al2O3 thickness and oxidant precursors on the interface composition and contamination in Al2O3/GaN structures

In this paper, we investigate the Al2O3/GaN critical buried interface of the next generation of gallium nitride (GaN)-based transistors using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and hard X-ray photoelectron spectroscopy (HAXPES). Results highlight that gallium oxidation at this interface is enhanced when increasing the Al2O3 thickness from 3 up to 20 nm. Gallium oxidation is reduced when using both O-3 and H2O as oxidant precursors, compared with only H2O during the growth of Al2O3. In addition, the O-3/H2O-based Al2O3 favors a reduction of contaminants such as hydrogen and carbon but enhances the presence of halides (Cl- and F-) at this Al2O3/GaN interface.