Optically excited terahertz emission from low-temperature-grown GaAs

We report on optically excited terahertz emission from low-temperature (LT)-grown GaAs. We have used 70 fs titanium-sapphire laser pulses with wavelengths of 800 nm to generate THz radiation pulses. The LT-GaAs layers are grown on semi-insulating GaAs substrates with GaAs buffer layers. The THz emission from the LT-GaAs surface is strong. No significant variation in the intensity of the THz emission is observed over several azimuthal angles between the polarization of the excitation laser pulse and the crystallographic orientation of the LT-GaAs. The refractive index, which is measured by detecting the THz signal passing through the LT-GaAs in the transmission configuration, is found to be 3.5 in the THz region.