Surface Termination Effect on Reflectance Spectra of GaAs

Dielectric response spectra of GaAs surfaces are determined using surface photoabsorption for surface conversion caused by Ga deposition and H adsorption on As-stabilized (001)-(2×4) surfaces and As desorption from As-rich (111)B-(2×2) surfaces. All of these spectra show common peaks at 2.6--3.0 and 4.5--4.7 eV, which coincide with critical points of bulk GaAs dielectric function. Model calculations show that the appearance of these critical points in the surface dielectric response can be explained by assuming that light absorption is quenched in the surface layer because of the terminated electronic wave functions at the surface.