Ballistic transport in p-type GaAs

The ballistic transport of electrons in the lightly p-type GaAs base of ballistic transistors has been measured at temperatures from 4.2 to 80 K and base lengths of 0.2, 1.7, and 5.7 μm. The transistors have n-type emitters, p-type base and collector with an undoped superlattice as the energy analyzer, and the electron energy is below that of the longitudinal optical phonon. Ballistic transport through the 5.7 μm base device is seen at up to 25 K while in the 0.2 μm transistor ballistic effects persist to liquid nitrogen temperature. A mean free path about 3 μm at 5 K is deduced from the experiments with little change up to 15 K. Calculation shows that neutral impurities dominate the scattering in this temperature range, and the calculated ballistic range of 3.2 μm is in excellent agreement with the experimental results.