Flat band potential determination of an electrolyte/semiconductor junction by an electro-optical method

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Abstract
When excitons have a lifetime sufficiently large at room temperature and when the semiconductor presents a uniform dopant distribution in the near surface region, if a convenient doping level is used it is possible to demonstrate an excitonic interference phenomenon. The latter may be modulated by varying the dc polarization bias V of the semiconductor/electrolyte junction and then oscillations of the ΔR/R electroreflectance response versus V appear. In this particular case of junctions, it is possible to correlate simply the period of the observed oscillations with (V−Vfb )1/2, where Vfb is the flat band potential value. A comparison of values obtained for Vfb in this way with those obtained by classical methods for three different semiconductors (CdS, GaAs, and ZnSe) shows the interest of this electro-optical method.