HIGH BREAKDOWN FIELD ( > 15MV/CM) ON CRYSTALLINE β-Ga_2O_3/GaN METAL OXIDE SEMICONDUCTOR DEVICES

摘要

We investigate the crystallinity effect of gallium oxide (Ga_2O_3) on the electrical properties of n-gallium nitride (GaN) metal oxide semiconductor (MOS) devices. The x-ray diffraction analyses of the oxide layer reveal preferential orientations due to reflections from the (019) and (024) planes. A thin strain-relieving layer (～ 20nm) of gallium oxynitride (GaON) with graded composition, as revealed by the x-ray photoemission spectroscopy, is shown to assist the oxide growth on GaN in the photo-enhanced chemical process. Improved MOS characteristics with high forward breakdown field E_(FB) > 15 MV/cm, high value of gate oxide barrier height Φ_B ～ 2.2 eV, and low interface state density D_(it) ～ 3.5 x 10~(11) cm~(-2)-eV~(-1) extracted by the conductance method are observed. These observations are ascribed to the formation of crystalline Ga_2O_3 layer on GaN as the oxide is transformed from a hydrous status into a monoclinic phase during a post-growth thermal annealing in O_2 ambience.