Improved microwave noise and linearity performance in GaN MISHEMTs on silicon with ALD Al2O3 as gate dielectric

In this work, enhanced noise and linearity performance in 0.25 μm gate-length AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MISHEMTs) on high-resistivity silicon substrate using atomic-layer-deposited (ALD) Al₂O₃ as gate dielectric is reported. High current gain cut-off frequency f_T above 40 GHz and low minimum noise figure NF_min of ~1.0 dB at 10 GHz were achieved. This noise performance is believed to be the best ever reported for GaN MISHEMT on Si at this gate-length. In addition, bias dependent DC, microwave and noise characteristics were measured on both the MISHEMT and convention HEMT with Schottky gate, and it was found that the microwave small signal and noise performance in MISHEMT have less dependence on the drain current as compared to the conventional HEMT. These results demonstrate that the ALD Al₂O₃/AlGaN/GaN MISHEMT on high-resistivity silicon substrate is promising for high-linearity low-noise-amplifier (LNA) applications.