FORWARD DELAY IN SCALED AL0.48IN0.52AS IN0.53GA0.47AS HETEROJUNCTION BIPOLAR-TRANSISTORS/

We present experimental measurements and numerical simulations of the intrinsic forward delay as a function of base thickness in abrupt junc tion n-p-n Al0.48In0.52As/In0.53Ga0.47As heterojunction bipolar transi stors. For base thicknesses up to 1350 angstrom and impurity concentra tion p = 1. 5 X 10(19) cm-3 we find that nonequilibrium electron trans port ensures that base transit delay is less than that in the 3000-ang strom-thick collector space-charge region. This provides an opportunit y to increase base thickness and reduce base resistance without sacrif icing the intrinsic forward delay time.