Abstract
The optically excited terahertz (THz) radiation source from proton-bombarded GaAs (GaAs:H + ) was investigated. The different time-resolved THz fields radiating from GaAs:H + and semi-insulating GaAs associated with their correlated mechanisms were compared and elucidated. The larger negative peak of THz field indicated that the dense ion-implantation process may introduce either an additional radiating mechanism except for the current surge effect, or an ultrafast carrier scattering process which dramatically reduces the falling time of photocurrent generated GaAs:H + .