Electrical and structural characterizations of crystallized Al2O3/GaN interfaces formed by in situ metalorganic chemical vapor deposition

Al2O3 films were grown in situ by metalorganic chemical vapor deposition at 900 °C on GaN of both Ga- and N-face polarities. High-resolution transmission electron microscopy revealed that the Al2O3 films were crystalline and primarily γ-phase. The Al2O3/Ga-GaN and Al2O3/N-GaN interfaces were both atomically sharp, and the latter further exhibited a biatomic step feature. The corresponding current-voltage (J-V) characteristics were measured on a metal-Al2O3-semiconductor capacitor (MOSCAP) structure. The leakage current was very high when the Al2O3 thickness was comparable with the size of the crystalline defects, but was suppressed to the order of 1 × 10−8 A/cm2 with larger Al2O3 thicknesses. The interface states densities (Dit) were measured on the same MOSCAPs by using combined ultraviolet (UV)-assisted capacitance-voltage (C-V), constant capacitance deep level transient spectroscopy (CC-DLTS), and constant capacitance deep level optical spectroscopy (CC-DLOS) techniques. The average Dit measured by CC-...

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