The electron affinity of HgCdTe

An accurate formula for electron affinity is necessary for the correct modeling of Hg1−xCdxTe devices. We show that the most commonly used formula is inaccurate. We construct a generalized equation for the electron affinity based on certain properties of the HgCdTe alloy system and select the experimental values to insert, producing a recommended formula that is useful in device modeling. We also find that in a graded HgCdTe structure, very nearly 2/3 of the bandgap change will appear in the conduction band. In addition, we explain why the electron affinity rule (conduction band offset equals the electron affinity difference) remains valid for HgCdTe–HgCdTe heterojunctions, even though it does not apply to heterojunctions in general.