Vibrational infrared spectroscopy of HgTe-CdTe superlattices

The current interest in HgTe-CdTe superlattices stems from their usefulness in advanced IR detectors, but for such applications it is necessary to have structures of high performance excluding atomic diffusion in neighbouring layers. Lattice vibration infrared (IR) spectroscopy is a good tool for checking the structural perfection of the superlattices. Analysis of the lattice vibration reflectivity spectra of Hg(1-x)Cd(x)Te alloys was used to obtain the concentration dependences of the oscillator strengths of the Hg-Te vibrations. A comparison with the oscillator strengths of the HgTe-CdTe superlattices deduced from their IR spectra was made. This permitted us to determine the composition and structural perfection of the layers and of the interfaces. The possibility in principle of growing HgTe-CdTe superlattices of high performance with abrupt layers and no traces of alloy in the interface was demonstrated.