Simulation and characterization of millimeter-wave InAlN/GaN high electron mobility transistors using Lombardi mobility model

A gate length of 0.2 μm InAlN/GaN high electron mobility transistor on SiC substrate is obtained with a maximum current gain cutoff frequency (fT) of 65.8 GHz and a maximum power gain cutoff frequency (fmax) of 143.6 GHz. Lombardi model, which takes interface roughness scattering into consideration, has been introduced to model the transconductance (gm) degradation. The simulated gm and fT with Lombardi model are 69% and 58% lower than the ones without considering interface roughness scattering, respectively. Further analysis show experimental gm, gate capacitance (Cg), and fT are consistent with results based on Lombardi model.