12.5 nm base pseudomorphic heterojunction bipolar transistors achieving fT=710GHz and fMAX=340GHz

The pseudomorphic collector structure is known to allow enhanced collector transport, facilitating higher current cutoff frequencies at lower current densities and junction temperatures compared to traditional single heterojunction structures. The performance of a 0.25×3μm2 pseudomorphic heteojunction bipolar transistors achieves peak fT of 710 GHz (fMAX=340GHz) at a collector current density of 20mA∕μm2. The same device achieves a fT∕fMAX of 540∕407GHz at a reduced current density of 7.5mA∕μm2. The epitaxial structure employs a 12.5 nm strained InGaAs base and 55 nm InGaAs collector, and exhibits a β of 115 and breakdown voltage of BVCEO=1.75V.