Gate length dependence of the speed of SSl circuits using submicron selectively doped heterostructure transistor technology.

Frequency dividers and ring oscillators have been fabricated with submicron gates on selectively doped AlGaAs/GaAs heterostructure wafers. A divide-by-two frequency divider operated up to 9.15 GHz at room temperature, dissipating 25 mW for the whole circuit at a bias voltage of 1.6V, with gate length ~0.35 microns. A record propagation delay of 5.8 ps/gate was measured for a 0.35 micron gate 19-stage ring oscillator at 77K, with a power of 1.76 mW/Gate, and bias voltage 0.88V. The maximum switching speed at room temperature was 10.2 ps/gate at 1. 03 mW/gate and 0.8V bias, for a ring oscillator with the same gate length. With a range of gate lengths on the same wafer fabricated by e-beam lithography, a clear demonstration of gate-length dependence on the propagation delay was observed for both dividers and ring oscillators.