Application of AlGaAs/GaAs HBT's to High-speed CML Logic Family Fabrication

This paper deals with the design consideration, fabrication process, and performance of the first small-scale integrated logic family including current-mode-logic (CML) inverter, or/nor, nand/or, exclusive or/nor gates, and master-slave flip-flops implemented using self-aligned AlGaAs/GaAs heterojunction bipolar transistors (HBT's). The HBT's incorporated in the IC's apply a 2.5-μm emitter design rule and exhibit a current gain of β = 40, cutoff frequency fT = 50 GHz, estimated CML gate-propagation delay time τpd = 24.7 ps, and nonthreshold logic gate-propagation delay time τpd = 12.3 ps. Successful operation for the developed logic circuits are predicted using a SPICE-F simulator, and are verified experimentally.