Interface Properties of Al2O3/n-GaN Structures with Inductively Coupled Plasma Etching of GaN Surfaces

The effects of the Cl2-based inductively coupled plasma (ICP) etching of GaN on the interface properties of Al2O3/GaN structures prepared by atomic layer deposition (ALD) were investigated. We used n-GaN layers grown on freestanding n+-GaN substrates with low dislocation density. The ICP etching caused slight disorder of the chemical bonds at the GaN surface and monolayer-level interface roughness at the Al2O3/GaN interface, resulting in poor capacitance–voltage (C–V) characteristics due to high-density interface states including nitrogen-vacancy (VN) related levels. The postannealing process in N2at 400 °C drastically improved theC–Vcharacteristics, probably owing to the partial recovery of the VN-related defects and the increased ordering of chemical bonds in the GaN surface region.