Topological insulator materials like HgTe exhibit unique electronic properties at their interfaces and so peculiar attention has to be paid concerning the growth optimization. Molecular beam epitaxy of tensile-strained HgTe/CdTe is investigated as a function of the growth temperature. Crystal quality is checked by using high resolution X-rays diffraction. By combining several material characterization techniques such as scanning transmission electronic microscopy, time-of-flight secondary ion mass spectroscopy and X-rays reflectivity, we report sharp interface morphology with nanometer-scale Hg/Cd diffusion lengths.