Energy Bands and Breakdown Characteristics in Al2O3/UWBG AlGaN Heterostructures

We report on energy bands and breakdown characteristics of Al2O3 dielectrics on ultra-wide bandgap (UWBG) AlGaN heterostructures. Metal-dielectric-semiconductor structures are important to sustain high fields needed for future high-performance UWBG transistors. Using systematic experiments, we determined the fixed charge density (> 1013 cm-2), the dielectric/interface, and electric fields in the oxide of under flat-band conditions in the semiconductor. Low gate-to-drain leakage current of up to 5 x 10-7 A/cm2 were obtained in the metal-oxide-semiconductor structures. In lateral metal-semiconductor-insulator test structures, breakdown voltage exceeding 1 kV was obtained with a channel sheet charge density of 1.27 x 1013 cm-2. The effective peak electric field and average breakdown field were estimated to be > 4.27 MV/cm and 1.99 MV/cm, respectively. These findings demonstrate the potential of Al2O2 integration for enhancing the breakdown performance of UWBG AlGaN HEMTs.