Excitonic interference effects which may be observed on the lowhyphen;field electroreflectance response of a semiconductor/electrolyte junction by varying the dc bias voltage at a constant wavelength are discussed in an attempt to generalize current results. Such effects are evaluated in a manner similar to that employed in analyzing conventional interference phenomena, but introducing some simplifying approximations which are also examined. The theoretical response turns out to be periodic in, and damped by, the square root of the band bending at the semiconductor surface in agreement with experimental results. Moreover, the first extremum is a minimum or a maximum according to whether the refractive index of the dead layer is smaller or greater than that of the region containing the excitons. These conclusions are applied to the analysis of the experimental data due to Shen, Siripala, Tomkiewicz, and Cahen lsqb;J. Electrochem. Soc.133, 107 (1986)rsqb; concerningnhyphen;CuInSe2, a very promising directhyphen;gap material for photoelectrochemical devices. Excitons are shown to exist at room termperature in this compound, in spite of the very small value of the exciton ionization energy. Furthermore, useful information is obtained on basic semiconductor parameters such as the donor concentration, the flatband potential, and the refractive index.
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