Diffusion mechanisms in intermixed HgTe/CdTe superlattices

The interdiffusion behaviour of Hg in annealed HgTe/CdTe superlattices due to rapid thermal annealing (RTA) has been investigated by double-crystal x-ray rocking curve (DCRC) and secondary-ion mass spectroscopy (SIMS) measurements. The sharp satellite peaks of the DCRC measurements on as-grown HgTe/CdTe superlattices show a periodic arrangement of the superlattice with high-quality interfaces. As the annealing time increases, the peak intensities corresponding to of the DCRC spectra decrease dramatically. The negative direction of the entropy change obtained from the diffusion coefficients as a function of the reciprocal of the temperature after RTA indicates that the Hg diffusion for the annealed HgTe/CdTe superlattices is due to an interstitial mechanism. The SIMS profiles of the Cd and the Hg concentration near the annealed HgTe/CdTe superlattice interfaces show a nonlinear behaviour for the Hg, due to an interstitial diffusion mechanism for the Hg composition. As the thickness of the CdTe barrier decreases, the diffusion coefficient increases. These results indicate that nonlinear interdiffusion behaviour is dominant for HgTe/CdTe superlattices annealed at and that the Hg and the Cd can more easily intermix in HgTe/CdTe superlattices with thinner CdTe barrier layers due to the thermal treatment.