Characteristics of atomic layer deposited Gd2O3 on n-GaN with an AlN layer
The interfacial and electrical properties of atomic layer deposited Gd2O3 with an AlN layer on n-GaN were investigated. According to X-ray photoelectron spectroscopy spectra, the formation of Ga–O bonds that is significant near the Gd2O3/GaN interface was suppressed near the AlN/Gd2O3/GaN and Gd2O3/AlN/GaN interfaces. Larger amounts of oxygen atoms across the dielectric layers were observed for AlN/Gd2O3/GaN and Gd2O3/AlN/GaN junctions, which in turn produced the dominant peak corresponding to O–Al bonds. The flatband voltage shift in capacitance–voltage hysteresis characteristics was highest for the Gd2O3/AlN/GaN junction, indicating the highest interface and oxide trap densities. In addition, AlN/Gd2O3/GaN and Gd2O3/AlN/GaN junctions showed the highest interface state densities in the energy ranges of 0.1–0.2 eV and 0.4–0.6 eV, respectively. The reverse leakage currents were explained by Fowler–Nordheim (FN) for Gd2O3/GaN and AlN/Gd2O3/GaN junctions and by trap assisted tunneling (TAT) for the Gd2O3/AlN/GaN junction.