Electron microscopy studies of the intermediate layers at the SiO2/GaN interface

As the first step toward understanding the electrical properties of SiO2/GaN systems, the interface was characterized using high-resolution scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS). An epitaxial crystalline intermediate layer with a thickness of similar to 1.5nm was observed at the SiO2/GaN interface. STEM-EDS analyses revealed that this intermediate layer contained gallium and oxygen and mostly comprised the epsilon-Ga2O3 phase. The epsilon-Ga2O3/GaN interface was atomically smooth and free from misfit dislocations despite lattice mismatch of similar to 8.0%, suggesting that the initial oxidation of GaN surfaces is crucial to achieve good interfacial properties. (C) 2017 The Japan Society of Applied Physics