Interface trap characterization of AlN/GaN heterostructure with Al2O3, HfO2, and HfO2/Al2O3 dielectrics

Abstract

The interfacial properties of AlN/GaN heterostructures with different dielectric layers such as Al2O3, HfO2, and HfO2/Al2O3 prepared by atomic layer deposition were investigated. Interface state density versus energy level plots obtained from the Terman method revealed the peculiar peaks at ∼0.25 eV for the samples with Al2O3 and HfO2/Al2O3 and at ∼0.52 eV for the sample with HfO2, associated with nitrogen vacancy-related defects. According to the parallel conductance method, both the interface and border traps were observed for the sample with Al2O3. However, the border traps were not observed with including an HfO2 layer. The lowest interface trap density and the reverse leakage current were obtained for the sample with an HfO2/Al2O3 bilayer. Analysis of x-ray photoelectron spectroscopy spectra obtained from the HfO2 layers showed the formation of Hf–Al–O bonding for the sample with HfO2 while such formation was not observed for the sample with HfO2/Al2O3. These results indicate the superior interfacial quality of AlN/GaN heterostructures with an HfO2/Al2O3 bilayer.