In-situ interdiffusion measurements in HgTe-CdTe superlattices

HgTe-CdTe superlattices have been proposed as a tunable narrow bandgap semiconductor (E/sub g/ approx.0.1 to 0.16 eV) having potential applications in the long wavelength infrared region. The usefulness of such narrow band gap optical material relies on the stability of the constitutent Hg, Cd, and Te atoms across the heterointerfaces of the superlattice structure (interdiffusion). Temperature dependent in-situ x-ray diffraction measurements have been carried out on several HgTe-CdTe samples to determine the extent of interdiffusion of the Hg, Cd, and Te atoms in the superlattice region. The estimated interdiffusion constants D(T) are based on the analysis of the x-ray satellite intensities as a function of time for given temperatures T. The results show that the diffused (1,1,1) HgTe-CdTe superlattices are intrinsically more stable than Hg/sub 1-x/Cd/sub x/Te alloys: the superlattice diffusion constants are considerably lower than those for alloys. The results further show that, even at room temperature, the lifetime of such a HgTe-CdTe superlattice device is probably limited and that it also seems to depend upon the environment.