Sub-30-ps ECL circuit operation at liquid-nitrogen temperature using self-aligned epitaxial SiGe-base bipolar transistors

The authors report the operation of emitter coupled logic (ECL) circuits at liquid-nitrogen temperature using self-aligned epitaxial SiGe-base bipolar transistors. A minimum ECL gate delay of 28.1 ps at 84 K was measured; this is essentially unchanged from the room-temperature value of 28.8 ps at 310 K. This delay number was achieved under full logic-swing (500-mV) conditions and represents an improvement of greater than a factor of 2 over the best reported value for 84 K operation. Lower-power ECL circuits have switching speeds as fast as 51 ps at 2.2 mW (112-fJ power-delay product) at 84 K. These results suggest that silicon-based bipolar technology is suitable for very-high-speed applications in cryogenic computer systems.< >