E⁺ e^- → H⁺ e^- v̄ in the two-Higgs-doublet model

We calculate the cross section for e⁺ e^- → H⁺ e^- v̄ in the two-Higgs-doublet model from one-loop diagrams involving top and bottom quarks. This process offers the possibility of producing the charged Higgs boson at the e⁺ e^- collider when its mass is more than half the center-of-mass energy, so that charged Higgs pair production is kinematically forbidden. The cross section receives contributions from both s-channel and t-channel processes; the s-channel contribution dominates for center-of-mass energies of 1 TeV and below. About 80% of the s-channel contribution comes from the resonant process e⁺ e^- → H⁺ W^-, with W^- → e^-v̄. The cross section is generally small, below 0.01 fb for tanβ>2, and falls with increasing tanβ.