Ultra High Speed Heterojunction Bipolar Transistor Technology

Scaling of HBTs for high circuit bandwidth and high current gain ( τf) and power gain ( maxf) cutoff frequencies is summarized. Key bandwidth limits include scaling of the collector-base junction, the emitter Ohmic contact resistivity, and greatly increased current density. Substrate transfer processes allow submicron collector scaling, and have produced HBTs with 20 dB power gain at 100 GHz. 295 GHz τf has been obtained. Key to continued progress is improvement of emitter contacts and reliable operation at ~ 610 A / 2cm current density