Ballistic transport in p-type GaAs

The ballistic transport of electrons in the lightly p-type GaAs base of bal listic transistors has been measured at temperatures from 4.2 to 80 K and b ase lengths of 0.2, 1.7, and 5.7 mu m. The transistors have n-type emitters , p-type base and collector with an undoped superlattice as the energy anal yzer, and the electron energy is below that of the longitudinal optical pho non. Ballistic transport through the 5.7 mu m base device is seen at up to 25 K while in the 0.2 mu m transistor ballistic effects persist to liquid n itrogen temperature. A mean free path about 3 mu m at 5 K is deduced from t he experiments with little change up to 15 K. Calculation shows that neutra l impurities dominate the scattering in this temperature range, and the cal culated ballistic range of 3.2 mu m is in excellent agreement with the expe rimental results. (C) 1999 American Institute of Physics. [S0003-6951(99)02 440-7].