Subpicosecond photoconductivity ofIn0.53Ga0.47As: Intervalley scattering rates observed via THz spectroscopy

We report on the transient photoconductivity of hot carriers in undoped bulklike ${\mathrm{In}}_{0.53}$ ${\mathrm{Ga}}_{0.47}$As observed via time-resolved terahertz far-infrared spectroscopy. For very dilute photoexcitation densities of <1×${10}^{15}$ ${\mathrm{cm}}^{\mathrm{-}3}$ and an initial excess carrier energy of 630 meV, we find that electrons have an effective intervalley L→Γ return time of 3.1 ps as measured via the increased electrical conductivity associated with Γ electrons. In contrast, a total conductivity risetime of ∼0.5 ps is observed for electrons with initial excess energy insufficient to cause intervalley scattering. The observed frequency dependent conductivity is analyzed via the Drude theory, allowing the determination of the temporal dynamics of the mobility at dilute excitation densities of ∼1×${10}^{14}$ ${\mathrm{cm}}^{\mathrm{-}3}$. © 1996 The American Physical Society.