Interface state characterization of ALD‐Al2O3/GaN and ALD‐Al2O3/AlGaN/GaN structures

We have characterized the interface states of Al2O3/GaN and Al2O3/AlGaN/GaN structures prepared by atomic layer deposition using the conventional and photo-assisted capacitance-voltage (C–V) measurements. In order to control the interface states, an N2O-radical treatment was applied to the GaN and AlGaN surfaces prior to the deposition of the Al2O3 layer. We observed good C–V behavior and a relatively low density of interface states for the N2O-radical treated Al2O3/GaN structure. To estimate the state density distributions at the Al2O3/AlGaN interface, we applied the photo-assisted C–V measurement to the Al2O3/AlGaN/GaN heterostructures. The present Al2O3/AlGaN structre showed higher interface state densities than the Al2O3/GaN structure. However, we found that the N2O-radical treatment is effective in reducing the density of interface states at the Al2O3/GaN and Al2O3/AlGaN systems (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)