Ultrafast heavy hole-phonon interactions in highly n-doped GaAs have been selectively studied with femtosecond absorption saturation measurements by tuning the pumpprobe photon energy just above the doped electron Fermi edge. A heavy hole-phonon scattering time of -3OOfs has been measured, which is consistent with that calculated by a numerical model. Accordingly, an optical deformation potential of about 31 eV has been estimated for this highly n-doped sample.