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.