The dependence of the optical properties on the Ti doping concentration in GaAs epilayers

Photoluminescence PL. and photoreflectance PR. measurements on nominally undoped and Ti-doped GaAs epilayers grown on GaAs substrates by liquid phase epitaxy have been carried out to investigate the dependence of the optical properties on the Ti doping concentration in the GaAs epilayers. As the Ti atomic mole fraction increases, the PL intensity corresponding to the excitons bound to neutral acceptors decreases, and the broadening parameter and the exciton energy obtained from the PR spectra increase. The variation of the PR broadening parameter is caused by the change in the surface states resulting from the Ti doping. Also, strong Burstein–Moss shifts are observed in Ti-doped GaAs epilayers. These results indicate that the PL intensity and the PR broadening parameter are affected significantly by a variation of the surface states resulting from the existence of the Ti interstitial impurities. q1999 Elsevier Science B.V. All rights reserved