  We report here a photoconductive material for THz generation and detection
with sub-picosecond carrier lifetime made by C12 (Carbon) irradiation on
commercially available semi-insulating (SI) GaAs. We are able to reduce the
carrier lifetime of SI-GaAs down to sub-picosecond by irradiating it with
various irradiation dosages of Carbon (C12) ions. With an increase of the
irradiation dose from ~1012 /cm2 to ~1015 /cm2 the carrier lifetime of SI-GaAs
monotonously decreases to 0.55 picosecond, resulting in strongly improved THz
pulse detection compared with normal SI-GaAs.
