Publication Date:
2016-01-05
Description:
Al 2 O 3 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 Al 2 O 3 films were crystalline and primarily γ -phase. The Al 2 O 3 /Ga-GaN and Al 2 O 3 /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-Al 2 O 3 -semiconductor capacitor (MOSCAP) structure. The leakage current was very high when the Al 2 O 3 thickness was comparable with the size of the crystalline defects, but was suppressed to the order of 1 × 10 −8 A/cm 2 with larger Al 2 O 3 thicknesses. The interface states densities ( D it ) 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 D it measured by CC-DLTS and CC-DLOS were 6.6 × 10 12 and 8.8 × 10 12 cm −2 eV −1 for Al 2 O 3 /Ga-GaN and 8.6 × 10 12 and 8.6 × 10 12 cm −2 eV −1 for Al 2 O 3 /N-GaN, respectively. The possible origins of the positive (negative) polarization compensation charges in Al 2 O 3 /Ga-GaN (Al 2 O 3 /N-GaN), including the filling of interface states and the existence of structure defects and impurities in the Al 2 O 3 layer, were discussed in accordance with the experimental results and relevant studies in the literature.
Print ISSN:
0021-8979
Electronic ISSN:
1089-7550
Topics:
Physics
