Pump-probe spectroscopy of low-temperature grown GaAs for carrier lifetimeestimation: arsenic pressure dependence of carrier lifetime during MBE crystal growth

We have performed reflection-type degenerate pump-probe spectroscopy to mea sure the carrier lifetime of GaAs grown by molecular beam epitaxy (MBE) at 250 degreesC under four different effective arsenic pressures. The temporal behavior of the reflected probe pulse intensity strongly depends on both t he wavelength and the intensity of the exciting laser pulse. The overall fe ature can be interpreted by the carrier-density- and wavelength-dependent r efractive index change caused by the bandgap shrinkage, band filling, and p lasma effect. We also found that the carrier lifetime depends on the effect ive arsenic pressure during the MBE growth, which is considered to determin e the density of the defects in the GaAs. A carrier lifetime of 1.9 ps was obtained when GaAs was grown under the highest effective arsenic pressure a t 250 degreesC and subsequently annealed at 650 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.