A 50-GHz static frequency divider and 40-Gb/s MUX/DEMUX using self-alignedselective-epitaxial-growth SiGeHBTs with 8-ps ECE

A static frequency divider with a maximum operating frequency of up to 50 G Hz and a multiplexer (MUX) and a demultiplexer (DEMUX) that both operate at 40 Gb/s were developed for future optical-fiber-link systems. These digita l circuits were fabricated using ultra-high-speed self-aligned selective-ep itaxial-growth SiGe-base heterojunction bipolar transistors (HBTs) with sel f-aligned stacked metal/in-situ doped poly-Si electrodes. These HBTs provid e a 95-GHz cutoff frequency, a 108-GHz maximum oscillation frequency, and a minimum emitter-coupled-logic (ECL) gate delay of 8 ps. The excellent resu lts from this digital chipset show that SiGe HBT technology, with its high reliability and cost-effectiveness, will play an important role in future m ulti-gigabit per second optical-fiber-link systems.