BALLISTIC TRANSPORT OF HOLES AND PHONON REPLICAS IN LIGHTLY DOPED GAAS

We study the motion of nonequilibrium light holes injected into very l ightly doped GaAs using a hot-hole three-terminal device. We observe d irectional multiple longitudinal-optical (LO) phonon emission by the h oles. Using transverse magnetic field we observed scattering of light holes into heavy-hole states after the first phonon emission. An unexp ected 18 meV shift of the phonon replica spectrum suggests that the Fe rmi 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 resul ts are compared with those obtained for electrons.