Ellipsometric profiling of HgCdTe heterostructures

Abstract

The application of ellipsometry in conjunction with step etching is demonstrated for determining compositional profiles of Hg1−xCdxTe heterostructures. Measurements of the ellipsometric ψ parameter can be directly correlated with composition, x, for 0.2<x<0.35, as long as the ellipsometric Δ parameter remains in the 146°–148° range. An approximate functional expression for the calibration of ψ versus x was determined to be ψ(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 ∼1000 Å.