Scaling and high-frequency performance of AlN/GaN HEMTs

Small- and large-signal RF characteristics were measured on AlN/GaN HEMTs with 80-160 nm gate length and 100-300 μm gate width. Consistent with the literature, current-gain cut-off frequency and maximum frequency of oscillation were found to increase with inverse gate length independent of gate width. For the first time, output power and efficiency were reported at the high end of X-band, and were comparable to the best reported at 2 GHz, consistent with that estimated from DC characteristics, and insensitive to gate length or width. These results suggest that the performance of AlN/GaN HEMTs is quickly catching up with that of the more mature AlGaN/GaN HEMTs and may be scaled to even higher frequency and higher power.