Cooling of photoexcited carriers in undoped andn-dopedGa0.47In0.53As studied within the first few picoseconds

Carrier cooling in ${\mathrm{Ga}}_{0.47}$ ${\mathrm{In}}_{0.53}$As at a lattice temperature of 30 K is investigated via transmission changes at frquencies approximately 200 meV above the energy gap. In an undoped sample a rapid recovery of the initial bleaching with time constants of 1 and 10 ps is observed representing the depletion of electron and heavy-hole states, respectively. In an n-doped sample a time constant of 3 ps is found reflecting achange of occupation of conduction-band states. The experimental data are in favorable agreement with model calculations taking into account carrier polar-optical interaction and band-gap renormalization.