Submicron transferred-substrate heterojunction bipolar transistors

We report submicron transferred-substrate AlInAs/GaInAs heterojunction bipolar transistors (HBT's). Devices with 0.4-μm emitter and 0.4-μm collector widths have 17.5 dB unilateral gain at 110 GHz. Extrapolating at -20 dB/decade, the power gain cutoff frequency fmaxis 820 GHz. The high fmax, results from the scaling of HBT's junction widths, from elimination of collector series resistance through the use of a Schottky collector contact, and from partial screening of the collector-base capacitance by the collector space charge.