For medium digital integration densities at high-speed of operation Si bipolar and SiGe
heterojunction bipolar transistors are available. Pseudomorphic AlGaAs/InGaAs HEMTs and GaAs HBTs
are in strong competition with those devices for the 40 Gbit/s high data rate communication.
Despite of the Johnson limit constraints also for the next generation of 80 Gbit/s, SiGe HBTs will
try to address as many chip functions as possible. Fig. 2.12 and Fig. 2.13 show the comparison of
several Si and SiGe (H)BT technologies, taken from recent publications
[45,69,117,141,197,308]. A behaviour is visible consistent with the
product of
and
(collector emitter breakdown voltage) obeying the Johnson limit,
which confirms the trade off between RF-power and speed for this technology. A large optimization
potential was suggested in [68] (e.g.
= 2 V,
= 113 GHz also shown in
Fig. 2.13). Recently published data for
and
can be fitted by a value of
210 GHz V.
values as high as 130 GHz have been reported in [199], unfortunately without
reporting the
value.