MOS Capacitors for Surface Barrier Electroreflectance Measurements

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Abstract
We describe a thin film technique of fabricating samples for surface barrier electroreflectance measurements. Aluminum oxide forms the dielectric spacer and semitransparent nickel is used for the field electrode. The resulting MOS capacitor is transparent from below 0.4 eV to at least 7.5 eV and has no low temperature limitation. Spectra have been obtained on a large class of semiconductor materials using this technique. Qualitative features of the optical response suggest that the surface potential is not clamped by slow surface states, even at room temperature. This method is therefore suitable for quantitative experiments in which the surface field is determined by an auxiliary measurement of surface conductance or capacitance. Application of these preparation techniques to other experiments is suggested.