Terahertz radiation in In$_{0.38}$Ga$_{0.62}$As, grown on a GaAs wafer with a metamorphic buffer layer under femtosecond laser excitation

The results of time-domain spectroscopy of the terahertz (THz) generation in a structure with an In$_{0.38}$Ga$_{0.62}$As, photoconductive layer are presented. This structure grown by molecular-beam epitaxy on a GaAs substrate using a metamorphic buffer layer allows THz generation with a wide frequency spectrum (to 6 THz). This is due to the additional contribution of the photo-Dember effect to THz generation. The measured optical-to-terahertz conversion efficiency in this structure is 10$^{-5}$ at a rather low optical fluence of $\sim$40 $\mu$J/cm$^2$, which is higher than that in low-temperature grown GaAs by almost two orders of magnitude.