Study of THz radiation from semiconductor surfaces excited by femtosecond laser pulses under laser illumination

The effect of continuous-wave (cw) laser illumination on THz radiation from semiconductor surfaces such as n- and p-type GaAs, semi-insulating (SI-) GaAs and SI-InP has been studied. The THz radiation power for SI-InP decreases under cw laser illumination, which is explained by the screening of the surface electric field by the photogenerated carriers. On the other hand, an increase of 40% of the THz radiation power is observed for SI-GaAs by cw laser illumination with 167 mW. The origin of this increase is discussed in relation to the metastable defect and temperature rise in SI-GaAs.