Electrical Properties of Metal–Insulator–Semiconductor Capacitors on Freestanding GaN Substrate

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The electrical properties of GaN metal–insulator–semiconductor (MIS) capacitors with as-grown SiO2, annealed SiO2, and SiNx insulators were investigated by capacitance–voltage (C–V), current–voltage (I–V), and time-dependent dielectric breakdown (TDDB) measurements. The MIS capacitor with the SiNx insulator was determined to have a lower interface trap density of 1×1011 cm-2 eV-1 than the MIS capacitors with the as-grown and annealed SiO2 insulators. In addition, the dielectric lifetime of the SiNx insulator was extrapolated to be more than 20 years at an even high voltage at room temperature. These results indicate that the high insulator/GaN interface quality and high reliability required for high-performance power devices can be achieved by the deposition of the SiNx insulator on GaN.