I. Introduction
Gallium-Nitride on Silicon based HEMTs offer excellent capabilities for low-cost high power applications at high frequencies. Thanks to improvements in the epitaxial growth and the fabrication processes, the operating frequency and output power steadily increased with time [1]–[3]. At W-band, impressive output powers have been reported for MMIC amplifiers based on GaN HEMTs grown SiC [4]. The performance of GaN-on-Si technology still lags GaN-on-SiC although single devices have shown some potential for W-band operation [5].