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

Abstract

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 f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> , MAG/MSG @ 220GHz, and reduced common-base stability from parasitic base inductance L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> and/or collector-emitter capacitance C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ce</sub> . The PA cells are realized using substrate-shielded non-inverted thin-film microstrip wiring to minimize L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ce</sub> , make small the feed lines to the multi-finger devices, and prevent parasitic substrate-mode excitation in the 12.8-ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> InP substrate.