Application of Urbach rule optical absorption to composition measurement of Cd1-yZnyTe

The optical absorption coefficient of Cd1-yZnyTe near the fundamental band edge was measured at room temperature using transmission spectroscopy. Like in other II-VI semiconductors, it was found that the absorption coefficient exhibits an exponential dependence on incident photon energy according to Urbach's rule. It was also found that the exponential parameters depend on composition, y, of Cd1-yZnyTe. A technique is described for determining the composition of Cd1-yZnyTe from optical transmission spectroscopy. This technique has been implemented in the manufacturing of Cd1-yZnyTe substrates for lattice matched epitaxial growth of HgCdTe.