Surface and bulk origin of the optical anisotropy of As-rich GaAs(001) andGa1−xInxAs(001)

Abstract

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 theanalysis of the position of this line as a function of indium concentration in Ga 1 - x In x As. Up to x 0.5, the peak energy dependence follows that of the nearby E 1 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.