AlN-Capped AlInN/GaN High Electron Mobility Transistors with 4.5W/mm Output Power at 40 GHz

Abstract

We report the characterization of GaN high electron mobility transistors (HEMTs) using a new AlN-capped AlInN/GaN epilayer structure developed to achieve high current densities and reduced gate leakage currents. Devices with gate lengths of 75 and 200 nm and various and source–drain separations were fabricated simultaneously, allowing the selection of the most favorable configuration for power performance. We show that, as anticipated, aggressive scaling of source–drain spacing and gatelength does not benefit power performance because of early breakdown and more pronounced short-channel effects. For a non-field-plated 0.2 µm gate length in a 4 µm source–drain gap, the new epitaxial structure achieved a power density of 4.5 W/mm at 40 GHz. To the best of our knowledge, this is the highest power reported at 40 GHz for AlInN/GaN-based transistors, and the first report of the large-signal performance of an AlN-capped AlInN/GaN-based HEMT.