A 277-GHz fmax transferred-substrate heterojunction bipolar transistor

We report a AlInAs-GaInAs transferred-substrate heterojunction bipolar transistor (HBT). The transferred-substrate process permits fabrication of narrow and aligned collector-base and emitter-base junctions, reducing the collector-base capacitance and increasing the device f
_max
. A device with aligned 0.7-μm emitter and 1.6-μm collector stripes has extrapolated 277 GHz f
_max
and 127 GHz f/sub /spl tau//, respectively.