A comparison of Si and GaAs E/D logic performance.

The relative merits of Si and GaAs enhancement/depletion logic gates are compared for lithographic rules of 1 micron and minimum gate lengths of 0.7 and 1.0 micron respectively, to within plus or minus 0.1 micron. An analytic description of ring oscillator delays is reviewed and applied to both cases. Good agreement is obtained with measured results. Our conclusions are that, using V(DD) = 4V for Si gates, GaAs logic gates are faster than Si logic gates by a factor of 1.5 and have a power dissipation five times lower. When SDHT (selectively doped heterojunction transistor) devices are included in the comparison, the transconductances are increased probably due to the higher input capacitance. The propagation delays are thereby reduced by a factor of 15% at 300K.