ELLIPSOMETRIC PROFILING OF HGCDTE HETEROSTRUCTURES

The application of ellipsometry in conjunction with step etching is demonstrated for determining compositional profiles of Hg1-xCdxTe heterostructures. Measurements of the ellipsometric psi parameter can be directly correlated with composition, x, for 0.2 < x < 0.35, as long as the ellipsometric DELTA parameter remains in the 146-degrees-148-degrees range. An approximate functional expression for the calibration of psi versus x was determined to be psi-(x) = 14.73-12.96x + 2.726x2, and is expected to be reasonably accurate over the entire range from x = 0 (HgTe) to x = 1 (CdTe). The accuracy of this technique in practice is generally within +/- 0.01 in x value, with a depth resolution of approximately 1000 angstrom.