400-GHz InP/GaAsSb DHBTs With Low-Noise Microwave Performance

We report self-aligned 0.3-μm emitter InP/GaAsSb/ InP DHBTs featuring a common-emitter current gain of 46 and cutoff frequencies f
_T
= 400 GHz and f
_MAX
= 322 GHz for devices implemented with a 20-nm C-doped base and a 75-nm InP collector. Our DHBTs display attractive noise properties with a minimum noise figure NF
_min
= 1.2 dB at 20 GHz, which is nearly independent of frequency over the 2-20-GHz measurement band. This represents an improvement of at least 2.3 dB with respect to previously published results for GaAsSb-based devices, due to process improvements that allow good RF characteristics to be maintained at the low current levels required for low noise operation. Analysis shows that the low-frequency NF
_min
is limited by the relatively low current gain values typical of III-V HBTs. InP/GaAsSb DHBTs could be attractive low-noise devices for higher frequencies.