Effect of thermal annealing on the optical properties of Liq-implanted GaAs

Photoreflectance PR.and Raman scattering measurements were carried out in order to investigate the donor compensation effects of Liq-implanted and annealed GaAs. As the energy of the Liq-implantation increased, the oscillation period of the PR spectrum was shorten because of a decrement in the surface electric field resulting from the compensation of donors due to Ga vacancy, which was also confirmed by the Hall effect measurements. The donor pagination as a function of the Liq injected energy was explained using the concept of the kinetic energy. While the intensities of the PR spectra increased remarkably after annealing the period of the Franz–Keldysh oscillation did not change. The intensity of the longitudinal optical phonon of the Raman spectra increased after annealing. These results indicate that the surface electric field of the GaAs decreases due to the donor compensation resulting from an increase in the Liq injection energy and that the crystallinity recovers after thermal annealing. q1999 Elsevier Science B.V. All rights reserved.