Multi-finger 250nm InP HBTs for 220GHz mm-wave power

We present here measured DC and RF performance of multi-finger 250nm InP HBTs intended for power amplifier design at high-mm, sub-mm-wave frequencies. The designs presented are in common-emitter and common-base configuration, having 24um periphery. Performance limitations for the PA cell have been identified and mitigated through novel design and layout - they include HBT thermal impedance, RF bandwidths ft and fmax, MAG/MSG @ 220GHz, and reduced common-base stability from parasitic base inductance Lb and/or collector-emitter capacitance Cce. The PA cells are realized using substrate-shielded non-inverted thin-film microstrip wiring to minimize Lb and Cce, make small the feed lines to the multi-finger devices, and prevent parasitic substrate-mode excitation in the 12.8-εr InP substrate.