Impact of etching process on Al2O3/GaN interface for MOSc-HEMT devices combining ToF-SIMS, HAXPES and AFM

•A combined approach based on HAXPES with ToF-SIMS and AFM was developed for HEMTs technology.•Lab-based HAXPES provides increased depth sensitivity compared to XPS, thus allowing a detailed analysis of GaN oxidation and stoichiometry at the critical buried Al2O3/GaN interface in a non destructive way.•ToF-SIMS depth profiling with high in-depth chemical resolution allows investigating the interface composition and contamination.•Lab-based HAXPES and ToF-SIMS results show that GaN stoichiometry is affected by oxidation and etching contaminants.•Results are completed by AFM showing a different morphology between structures etched and structures free from etching. In this work we present the effect of inductively coupled plasma reactive ion etching (ICP-RIE) combined with atomic layer etching (ALE) on the Al2O3/GaN interface for MOSc-HEMT devices. Time of flight secondary ion mass spectrometry (ToF-SIMS) and hard x-ray photoelectron spectroscopy (HAXPES) highlight an increase of the N/Ga ratio near the interface after etching. ToF-SIMS profiles also show the presence of impurities (H, C, B) at this interface. Atomic force microscopy (AFM) also illustrates a change of the GaN surface morphology for the etched sample.