Interfacial and electrical properties of Al2O3/GaN metal–oxide–semiconductor junctions with ultrathin AlN layer

Abstract

Ultrathin AlN layer deposited by atomic layer deposition (ALD) was employed in Al2O3/GaN metal–oxide–semiconductor (MOS) capacitors, and their interfacial and electrical properties were investigated using X-ray photoelectron spectroscopy (XPS) and current–voltage (I–V) and capacitance–voltage (C–V) measurements. XPS analyses revealed that the diffusion of N atoms into Al2O3 and the degradation of Al2O3 film quality were significant for the thickest Al2O3 (10 nm). The sample with a 10-nm-thick Al2O3 layer produced the highest leakage current and trap density. These results may result from the deteriorated interface characteristics near the AlN layer caused by long growth time. Therefore, it is suggested that the Al2O3 thickness (and optimal growth time) is a key factor in Al2O3/AlN/GaN MOS capacitors.