Extended X-ray Absorption Fine Structure Investigation of Arsenic in HgCdTe: the Effect of the Activation Anneal

Extended x-ray absorption fine structure (EXAFS) investigation was carried out on two arsenic-doped HgCdTe samples. Arsenic incorporation was achieved with a non-conventional radiofrequency plasma source in a molecular beam epitaxy reactor. Both samples were taken from the same epitaxial run. One of these samples followed a 400°C activation anneal under Hg pressure. EXAFS was used here to probe the local environment around arsenic, and the experimental data were fit through first-principle calculations to extract a quantitative description of the arsenic site transfer upon annealing. Arsenic neighbors are described in terms of chemical nature, numbers and distances. Arsenic was found to be involved mostly in non-crystalline structures, either an As₂Te₃ glass or an AsHg compact structure. The effect of annealing is to break down the chalcogenide glass, thus favoring the compact AsHg structure. EXAFS results were compared to 77 K Hall-effect measurements, and a very good correlation was found. These findings were compared to the commonly admitted scenario for arsenic site incorporation and transfer upon annealing and provided a new picture and the first experimental evidence of the site transfer.