InGaP/GaAsSb/InGaAsSb/InP Double Heterojunction Bipolar Transistors With Record ft of 813 GHz

We fabricated InGaP/GaAsSb/InGaAsSb/InP double heterojunction bipolar transistors (DHBTs) with an aggressive lateral and vertical scaling technology to improve the current gain cutoff frequency (f
_t
) further. A 13-nm-thick GaAsSb/InGaAsSb base and a 40-nm-thick InP collector are used to reduce electron transit time. In addition, the width of the base electrode on each side of the emitter is reduced to about 0.05 μm to suppress increases in parasitic collector capacitance. A fabricated DHBT with the emitter size of 0.24 μm × 7.8 μm exhibits maximum differential current gain of ~95 and collector-emitter breakdown voltage of 2.6 V. At a collector current density of 18 mA/μm
²
, the DHBT exhibits f
_t
of 813 GHz, which is the highest among all types of transistors measured at a room temperature.