SUBPICOSECOND PHOTOCONDUCTIVITY OF IN0.53GA0.47AS - INTERVALLEY SCATTERING RATES OBSERVED VIA THZ SPECTROSCOPY

We report on the transient photoconductivity of hot carriers in undope d bulklike In0.53Ga0.47As observed via time-resolved terahertz far-inf rared spectroscopy. For very dilute photoexcitation densities of <1X10 (15) cm(-3) and an initial excess carrier energy of 630 meV, we find t hat electrons have an effective intervalley L-->Gamma return time of 3 .1 ps as measured via the increased electrical conductivity associated with Gamma electrons. In contrast, a total conductivity risetime of s imilar to 0.5 ps is observed for electrons with initial excess energy insufficient to cause intervalley scattering. The observed frequency d ependent conductivity is analyzed via the Drude theory, allowing the d etermination of the temporal dynamics of the mobility at dilute excita tion densities of similar to 1x10(14) cm(-3).