Characterization study of a HgTe-CdTe superlattice by means of transmission electron microscopy and infrared photoluminescence

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Abstract
We report the first transmission electron microscopy (TEM) study of a HgTe-CdTe superlattice. The superlattice consists of 250 layer pairs of HgTe-CdTe on a (100) CdTe substrate and was grown at 175 °C by molecular beam epitaxy. Vertical cross-section TEM images show a highly regular structure of the superlattice from the CdTe substrate to the free surface, indicating that interdiffusion effects at interfaces are minimal. Diffraction patterns taken from the first 30 pairs of layers of the superlattice from the CdTe buffer layer show a series of satellite spots up to the sixth order. This implies that the interfacial sharpness of this HgTe-CdTe superlattice is comparable to those interfaces of high quality III-V semiconductor superlattices. The HgTe-CdTe superlattice exhibits an infrared photoluminescence peak at 357 meV, in reasonable agreement with theoretical predictions of its band gap.