Optical properties and interdiffusion of (001) HgTe/Hg1-xCdxTe superlattices

Interdiffusion in HgTe/Hg1-xCdxTe superlattices has been investigated by means of changes in their optical properties. The energy of the lowest interband transition, H1-->E1, which is calculated using a finite HgTe/Hg1-xCdxTe interface width, is compared with the experimental value in order to ascertain the width and shape of the interface. The results, which can be explained better if interdiffusion is linear rather than nonlinear, are strongly dependent on the sample. Moreover, the observed interdiffusion in the superlattice with the smallest diffusion coefficient is larger than the interdiffusion which occured during growth: the absorption coefficient of as-grown superlattices is independent of time spent at the growth temperature contrary to predictions using experimentally determined interdiffusion results. Apparently, the results of the interdiffusion experiments depend on the thermal history of the sample.