Ballistic transport of holes and phonon replicas in lightly doped GaAs

We study the motion of nonequilibrium light holes injected into very lightly doped GaAs using a hot-hole three-terminal device. We observe directional multiple longitudinal-optical (LO) phonon emission by the holes. Using transverse magnetic field we observed scattering of light holes into heavy-hole states after the first phonon emission. An unexpected 18 meV shift of the phonon replica spectrum suggests that the Fermi level is pinned in an impurity band, in the gap, formed in the p⁺ regions. We find that the mean-free path of light holes, with energy just below the LO phonon emission threshold, is 300-360 nm. The results are compared with those obtained for electrons.