Carrier Dynamics of ErAs:GaAs_1-xBi_x using infrared pump, Terahertz probe Spectroscopy

We study the ultrafast carrier dynamics in low and high Er embedded Bi doped GaAs, ErAs:GaAs_1-xBi_x, using infrared pump terahertz probe spectroscopy as a function of pump energies from 0.5 eV (2480 nm) to 1.0 eV (1240 nm) at a pump fluence of 0.042 J/cm² (100 mW pump power). Terahertz of bandwidth 0.2 THz to 2 THz has been used to probe the free carrier response after photoexcitation. The measurement was carried out by tracing the infrared pump pulse delays positioned at the peak of the terahertz wave, generated by using a tilted pulse front method and detected by using electrooptic sampling method. Two relaxation times are observed, with one in picosecond and another in nanosecond time scale, from the two energy levels and their corresponding decay amplitudes have been obtained.