SURFACE PROCESSES AT ELECTROLYTE HIGHLY DOPED SEMICONDUCTOR INTERFACES ANALYZED BY ELECTROREFLECTANCE MODELING

Electroreflectance spectra from a highly doped n-GaAs sample in an alk aline electrolyte have been modelled, taking into account both Franz-K eldysh and bandfilling (Moss-Burstein) effects. Comparisons are made b etween theory and experiment, and the evolution of spectra calculated for a wide range of space-charge potentials is found to follow accurat ely that of the experimental spectra with applied potential. The propo rtion of the interfacial a.c. and d.c. potential differences accommoda ted outside the semiconductor can also be obtained from the analysis, allowing us to extract the Fermi level pinning and to associate this w ith possible surface chemical reactions. The importance of heavy-dopin g effects is also briefly discussed, and the inclusion of band-filling in the modelling of the electroreflectance spectra of highly doped n- GaAs is shown to be essential if a quantitative fit is to be obtained.