X-ray-absorption fine-structure studies of Hg1-xCdxTe and Hg1-xMnxTe bond lengths: Bond relaxation and structural stability of ternary alloys


Bond lengths in the narrow-band-gap semiconductor alloys Hg1-xCdxTe and Hg1-xMnxTe have been deduced using x-ray-absorption fine-structure techniques. The nearest-neighbor bond lengths, for both alloy systems, are found to be constant as a function of alloy composition within the experimental uncertainties of 0.01. These results contradict the predictions of some recent theories for Hg1-xCdxTe alloys, finding the Hg-Te and Cd-Te bond lengths to be decreasing in spite of the lattice constant increasing with x. The bond relaxation in several III-V, II-VI, and II-VI-based diluted magnetic semiconductor (DMS) ternary alloys is found to be quantitatively proportional to the ratio of bond bending to bond-stretching force constants. Hg1-xCdxTe and DMS alloys, including Hg1-xMnxTe, are found to have the largest amount of bond relaxation. For DMS's, this is attributed to tetrahedral bond weakening resulting from hybridization of anion p and Mn 3d orbitals thereby decreasing the amount of charge available for the making of sp3 bonds.

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Physical Review B