Formation of high-quality SiO2/GaN interfaces with suppressed Ga-oxide interlayer via sputter deposition of SiO2

While the formation of a GaO x interlayer is key to achieving SiO2/GaN interfaces with low defect density, positive fixed charge is rather easily generated through the reduction of GaO x layer if the annealing conditions are not properly designed. In this study, we minimized the unstable GaO x layer by sputter SiO2 deposition. Negligible GaO x growth was confirmed by synchrotron radiation X-ray photoelectron spectroscopy, even when post-deposition oxygen annealing up to 600 degrees C was performed. A MOS device with negligible capacitance-voltage hysteresis, stable flat-band voltage, and low leakage current was demonstrated by performing oxygen and forming gas annealing at temperatures of 600 degrees C and 400 degrees C, respectively.