InPHEMT downscaling for power applications at W band

We have developed new solutions for InP high-electron mobility transistor (HEMT) scaling for power applications at W band. We have shown that the use of a small barrier thickness in order to respect the aspect ratio for a 70-nm gate length results in a significant kink effect and high gate source capacitances. We have also shown through a theoretical study that a structure containing an InP layer between the cap layer and the barrier would support both the frequency performances and the breakdown voltage. Thus, we propose an HEMT structure containing a thick InP/AIInAs composite barrier and where the gate is buried into the barrier. This enables us to respect the aspect ratio and simultaneously to obtain an important drain current density without observing any kink effect. Moreover, we have applied this process to structures containing innovative large band-gap InP and InAsP channels. We have achieved the best frequency performances ever reached for an InP channel HEMT structure. Power measurements at 94 GHz were performed on these devices. The InAsP channel HEMT demonstrated a maximum output power of 260 mW/mm at 3 V of drain voltage with 5.9-dB power gain and a power-added efficiency of 11%. These results are favorably comparable to the state-of-the-art of InP-based HEMT at this frequency.