Dynamics of Photoexcited GaAs Band-Edge Absorption with Subpicosecond Resolution

Abstract

Time-resolved measurements of optically induced changes in the near-band-gap transmission spectrum of GaAs at 80\ifmmode^\circ\else\textdegree\fi{}K, following excitation with an ultrashort laser pulse, provide a means of directly monitoring the hot-carrier distribution as it cools to the lattice temperature with a time constant of 4 psec. Exciton screening and band-gap renormalization are observed to occur in less than 0.5 psec.