High-Current-Gain InP/GaInP/GaAsSb/InP DHBTs With $f_{T} = \hbox{436}\ \hbox{GHz}$

Combining a pseudomorphically strained (Ga,In)P emitter with a GaAs
_0.6
Sb
_0.4
base effectively eliminates the emitter heterojunction type-II conduction band offset in InP/GaAsSb double heterojunction bipolar transistors (DHBTs). A peak f
_T
of 436 GHz at J
_C
= 10 mA/mum
²
, with BV
_CEO
= 3.8 V, is achieved with 0.6 times 5 mum
²
InP/GalnP/GaAsSb DHBTs with a 75-nm InP collector. Compared to a binary InP emitter, the (Ga,In)P emitter doubles the DC current gain from 166 to 338 for otherwise identical devices. These are the highest DC current gain and cutoff frequencies to date in uniform base GaAsSb DHBTs. The gain improvement reported here will greatly facilitate device design tradeoffs that are encountered while scaling InP/GaAsSb DHBTs toward higher frequencies by allowing higher base doping levels and smaller emitter geometries.