Photoreflectance study on carrier collisions in near-surface region of n-type GaAs grown by MOCVD

The influence of carrier scatterings on the Franz-Keldysh (FK) effect in the near-surface region of n-type GaAs has been investigated by photoreflectance (PR) spectroscopy. The PR spectra associated with the direct transition have been measured over a temperature range of 20 to 300 K. To determine the broadening energy due to carrier scattering, the PR spectra have been analyzed by a one-electron FK theory including the effects of field inhomogeneity and non-flat band modulation. The broadening energies thus obtained have been discussed in terms of the relaxation times responsible for carrier mobilities in bulk-GaAs.