Mass transport during photochemical oxidation of Hg1−xCdxTe

Abstract

We report determination of the mechanism of photochemical oxide growth (after initial film formation) when transport through the film dominates. Photochemical oxides grown in different ambients, i.e., O2 or N2O, are found to have different stoichiometry, especially at the ambient/oxide interface. Oxides grown in O2 with ultraviolet light exhibit Hg-rich surface layers, however growth in N2O often results in Hg-depleted surfaces. By sequentially oxidizing Hg1−xCdxTe epilayers in these ambients and analyzing the in-depth atomic profiles with Rutherford backscattering spectrometry and secondary ion mass spectrometry, the dominant diffusion mechanism is determined. Investigation of the migration of oxygen during the oxidation is carried out by oxidation in an 18O enriched ambient. We conclude that growth of these photochemical oxides involves both the diffusion of the substrate elements and oxygen, with the oxidation occurring primarily at the oxygen-oxide interface.