Graded base type-II InP/GaAsSb DHBT with fT=475 GHz

The first demonstration of a type-II InP/GaAsSb double heterojunction bipolar transistor (DHBT) with a compositionally graded InGaAsSb to GaAsSb base layer is presented. A device with a 0.4×6 μm
²
emitter dimensions achieves peak f
_T
of 475 GHz (f
_max
=265 GHz) with current density at peak f
_T
exceeding 12 mA/μm
²
. The structure consists of a 25-nm InGaAsSb/GaAsSb graded base layer and 65-nm InP collector grown by MBE with breakdown voltage /spl sim/4 V which demonstrates the vertical scaling versus breakdown advantage over type-I DHBTs.