InP/GaAsSb DHBTs With 500-GHz Maximum Oscillation Frequency

We report the realization of 0.3-μm emitter InP/GaAsSb/InP DHBTs with cutoff frequencies
f
_T
= 365 GHz and
f
_MAX
= 501 GHz. Our devices were implemented with a 15-nm C-doped graded base and a 125-nm InP collector and feature a peak current gain β = 35, with a base sheet resistance
R
_SH
= 1160 Ω/sq. The present transistors are the first InP/GaAsSb DHBTs to feature
f
_MAX
= 500 GHz, according to three extraction schemes. The present transistor performance is limited by an undepleted collector layer associated with a doping tail extending from the subcollector.