The effect of channel dimensions on the millimeter-wave power performance of a pseudomorphic HEMT

The authors study the effect of channel dimensions on the millimeter-wave power performance of a double-recessed pseudomorphic high electron mobility transistor (PHEMT). The choice of channel recess dimension, specifically the gate to drain n+ ledge separation (Lgd), seemed to have the most pronounced effect on transistor's power performance. Gate-drain capacitance, output conductance, drain delay (unity current gain frequency) and reverse breakdown voltage were all strong functions of Lgd. With this parameter optimized, a PHEMT exhibited the best power performance yet reported at Ka-band and state-of-the-art performance at Q-band. A Q-band MMIC power amplifier using an existing design was also realized. The two-stage amplifier exhibited 500 mW of ouput power with 7 dB gain and 15% PAE at 40 GHz. This result is the best published performance for a MMIC at this frequency.<>