  We have used a three-dimensional pseudo-classical Monte Carlo simulation to
investigate the effects of As+ ionimplantation on pulsed terahertz radiation
emitters. Devices based on surface-field emitters and photoconductive switches
have been modelled. Two implantations of As+ ions at 1.0 MeV and 2.4 MeV were
found to produce a uniform distribution of vacancies over the volume of GaAs
contributing to THz generation in these devices. We calculate that
ionimplantation increases the THz bandwidth of the devices with the cost of
decreasing the spectral intensity at lower THz frequencies.
