We study the influence of ionized impurity scattering on the electron transport in resonant-phonon-assisted terahertz （THz） quantum-cascade lasers （QCLs）. We treat the ionized impurity scattering rates within the single subband static screening approximation. We find that the ionized impurity scattering supplies an additional current channel across the device,and affects the electrondistribution in different subbands. We conclude that the ionized impurity scattering should be taken into account in the study of the transport properties of resonant-phonon-assisted THz QCLs.
