FEMTOSECOND CARRIER KINETICS IN LOW-TEMPERATURE-GROWN GAAS

The carrier energy distribution and recombination kinetics in low-temperature-grown and annealed GaAs (with 1% excess arsenic occurring as microclusters/point defects) have been time resolved at 295 K through luminescence upconversion and correlation spectroscopy using an 80 fs, 720 nm Ti:sapphire laser. We infer that the radiative recombination coefficient is the same in GaAs:As as in normal GaAs and that both electron and hole trapping times are about 1 ps. Luminescence is detected at energies as much as 300 meV below the band gap and is identified with delocalized states induced by excess As. We observe that the presence of excess As gives photoexcited carriers a higher initial temperature than in GaAs. Finally, since the carrier density decays faster than the emitted optical phonons, energy relaxation is inhibited more effectively than in normal GaAs.