Surface dielectric change of GaAs determined from surface photo-absorption spectra

We compare surface photo-absorption spectra observed for various surface structural transformations on GaAs (001) and (111)B surfaces. Surface conversions investigated here are (i) from (2×4) to (3×1) caused by Ga deposition, (ii) from (2 × 4) to (1 × 1) caused by H-adsorption on GaAs (001) surface, and (iii) from (2 × 2) to (√19 × √19) caused by As desorption on (111)B surface. The change in surface dielectric function is determined for each of the surface conversions using curve fitting based on the harmonic oscillator model of the dielectric function. Common peaks that coincide with the critical points of the dielectric function of GaAs are found in the spectra of the surface dielectric change thus determined. This indicates that the effect of bulk electronic states modified by the surface is significant in the surface photo-absorption spectra.