ISSN - 10980121, Physical Review B - Condensed Matter and Materials Physics, 2003, vol. 67, p. 2453131-2453134
Surface and bulk origin of the optical anisotropy of As-rich GaAs(001) and Ga1-xInxAs(001)
We show experimentally and theoretically that the characteristic line at 3 eV in the reflectance anisotropy (RA) spectra of As-rich (001) GaAs has a mixed bulk and surface origin. The experimental observations rely on the analysis of the position of this line as a function of indium concentration in Ga1-xInxAs. Up to x ≈0.5, the peak energy dependence follows that of the nearby E1 bulk optical transition, which shows that the line is not of pure surface character. The same conclusion is drawn from the mere fact that the line position depends on x since, because of indium surface segregation and bond length conservation, the energy of a purely surface-related transition should weakly depend on bulk composition. The combined relevance of surface states and surface-perturbed bulk states is shown by an ab initio density functional theory local dnesity approximation calculation of the RA spectrum of As-rich (001) GaAs, which also explains the observed oxygen-induced changes of the RA spectrum.