Large-signal linearity in III-N MOSDHFETs

The authors report the output RF signal distortions in the novel SiO/sub 2/-AlGaN-InGaN-GaN metal-oxide-semiconductor double heterostructure FET (MOSDHFET) device structure. Their comparative studies of MOSDHFETs and Schottky gate type DHFETs fabricated on the same wafer show significantly improved RF output signal linearity in MOSDHFETs at high-input signals. At the RF output powers close to saturation, the relative level of the second and third harmonic powers in MOSDHFETs was found to be less than -30 dB, which is about 15-20 dB lower as compared to identical geometry DHFET. This improvement is attributed to a better linearity of the MOSDHFET current-gate voltage characteristics.