Systematic pump-probe terahertz wave emission spectroscopy of a photoconductive antenna fabricated on low-temperature grown GaAs

The ultrafast terahertz (THz) peak amplitudes and the temporal profiles of THz electromagnetic waves created by the probe pulse as a function of the pump-probe delay time were measured. The fast recovery of the peak amplitude and the increase of the spectral amplitude in the low frequency regime of the THz wave occurred by the defect levels in the low temperature (LT)-GaAs samples. It was observed that, with a strong pump-pulse excitation, the THz electromagnetic waves showed an increase of the spectral amplitude in the low-frequency regime. It was also observed that the increase continued till the carriers created by the pump pulse were trapped by the defect levels in the LT-GaAs.