11.7 W/mm Continuous Wave Output Power in X-Band AlN-Buffer HEMTs

Power amplifiers (PAs) using HEMTs with aluminum nitride (AlN) buffer layers promise superior thermal performance over the current generation of GaN-buffer HEMT PAs. However, the continuous-wave (CW) output power densities from AlN-buffer HEMTs have been limited to <6 W/mm so far. This work presents the advancement in the large-signal RF performance of AlN-buffer HEMTs with a 2× improvement in CW output powers. AlN-buffer HEMTs with 180 nm gate length and 2 µm source-drain distance fabricated on 100 mm SiC substrates, show on-currents of 1.1 A/mm and breakdown voltage ∼100 V. On-wafer load-pull power sweep measurements conducted at 10 GHz demonstrated a maximum CW power output (P out ) of 5.5 W/mm at 28 V and 11.7 W/mm at 50 V bias. At 50 V, the peak PAE of 49 % had an associated P out 11.32 W/mm and linear gain of 9.35 dB. This significant power enhancement, coupled with AlN buffer HEMT's inherent thermal superiority, paves the way for its widespread adoption in critical RF applications.