Effect of Al2o3 Thickness and Oxidant Precursors on the Interface Composition and Contamination in Al2o3/Gan Structures

In this paper, we discuss the combined characterization by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and hard x-ray photoelectron spectroscopy (HAXPES) of the Al2O3/GaN interface for the next generation of MOS-gate GaN-based devices. The final properties of these devices strongly depend on the quality of this critical interface. The results highlight that gallium oxidation at this interface is enhanced when increasing atomic layer deposited (ALD) Al2O3 thicknesses from 3 nm up to 20 nm. Moreover, we highlight how Al2O3 (O3/H2O)/GaN structures reduce the oxidation of gallium compared to Al2O3 (H2O) structures, where O3 and H2O are the oxygen precursors for ALD of Al2O3. In addition, through ToF-SIMS measurements we show the effect in terms of contaminants (hydrogen, carbon, halide) at the Al2O3/GaN interface depending on the oxygen precursor used.