Frequency limits of GaAs and InP field-effect transistors at 300 K and 77 K with typical active-layer doping

InP FET's with active layer doping of 10
¹⁷
donors/ cm
³
have limiting values of f
T
roughly fifty per cent higher than those of equivalent GaAs devices for lengths ranging from 0.5 µm to 3 µm at 300 K, and from eighty percent to forty percent higher in this gate length range at 77 K.