High speed GaAs digital integrated circuit with clock frequency of 4.1 GHz

A maximum clock frequency of 4.1 GHz was obtained for a GaAs digital integrated circuit using deep recess normally-on GaAs MESFETs with 1.2 ?m long gate and interdigitated Schottky diodes. The Ti/Pt/Au gate electrode was made by a lift-off technique with conventional photolithography. The minimum propagation delay of a NAND/AND gate was estimated to be 100 ps/gate for a fan-out of 2 from the self-oscillation frequency of the master-slave flip-flops.