Investigation of the Effects of Forming Gas Annealing on Al2O3/GaN Interface

In this work, the effects of post-deposition annealing in forming gas ambient on the structure of the Al2O3/GaN interface are investigated. Using capacitance–voltage (C–V) and conductance–frequency (G–f) measurements, the quality of Al2O3/GaN metal–insulator–semiconductor (MIS) devices subjected to different annealing conditions was assessed. Annealing at 350°C for 10 and 20 min resulted in the lowest density of trap states (< 1011 cm−2eV−1), while higher-temperature annealing resulted in increased density of interface traps. Scanning transmission electron microscopy, energy-dispersive x-ray spectroscopy (STEM/EDS), and x-ray photoelectron spectroscopy (XPS) were used to determine the impact of the anneal on the structure of the oxide and interface. It was found that after annealing at 600°C for 20 min, the oxide structure was not significantly changed, though the density of interface states was found to increase by nearly an order of magnitude. These results suggest that the post-deposition annealing of Al2O3/GaN in forming gas passivates defects at the interface but does not cause significant structural change away from the interface.