Characterization of optically excited terahertz radiation from arsenic-ion-implanted GaAs

This work characterizes the optically excited terahertz (THz) radiation fro m arsenic-ion-implanted GaAs (GaAs:As+). We observed phase reversal in the emitted THz radiation field after the semi-insulating GaAs substrate was im planted. The peak amplitude of the emitted THz field increased from 25 mV/c m to 100 mV/cm after thermal annealing. This trend confirms the recovery in crystallinity of the as-implanted GaAs :As+ after annealing. By introducin g a magnetic field, we observe a blue shift of the center frequency in the THz power spectrum from 0.57 THz for the as-implanted CaAs : As+ to 1 THz f or furnace-annealed samples. Analysis of the blue-shifted spectra and unsym metrical pulse shapes allows us to infer the increasing importance of the c ontribution of another unknown mechanism to the THz radiation from the GaAs :As+ samples after annealing. This is also explained satisfactorily by the crystallinity of the as-implanted and furnace-annealed GaAs : As+. Further, the effective carrier mobilities of as-implanted, rapid-thermal-annealed, and furnace-annealed GaAs : As+ are determined for the first time as 0.6, 2 , and 15 cm(2)/Vs respectively according to the THz data.