Precise measurements of the dispersion of the index of refraction for Cd1−xZnxTe alloys

Abstract

By using a prism coupler technique in conjunction with reflectivity measurements, we have obtained highly accurate relations for the dispersion of the indices of refraction n for a series of MBE-grown Cd1−xZnxTe alloys. Initially, the prism coupler technique was used to determine n at discrete wavelengths with an accuracy of at least 0.1%, and also to concurrently determine the epilayer thicknesses with an uncertainty of less than 0.5%. Having obtained precise values for both n (at discrete wavelengths) and the thicknesses of the Cd1−xZnxTe epilayers, we were then able to correctly decipher the values for n at the maxima and minima of the reflectivity spectra observed on the above epilayers, and thereby generate a continuous variation of the indices of refraction as a function of wavelength. Fitting the dispersion of n in each alloy to a Sellmeier-type dispersion relation, we have obtained the dependence of the constants appearing in this relation on the alloy concentration. This enables one to predict n not only as a function of wavelength, but also as a function of alloy composition.