Properties of HgTe–Hg0.15Cd0.85Te superlattices grown by molecular-beam epitaxy

The structural and optical properties of a series of molecular-beam epitaxy (MBE) grown HgTe–Hg0.15Cd0.85Te superlattices (SL) have been studied. Vertical cross-section transmission electron microscopy studies show no evidence of Hg interdiffusion, confirming the high quality of these multilayered structures. Transmittance and reflectance measurements were performed on each sample and analyzed to obtain optical absorption coefficients. The absorption coefficient versus photon energy spectra show consecutive rises and plateaus characteristic of two-dimensional quantum structures. A two-band tight-binding model was used to analyze the absorption data and identify the quantum transitions. The observation of both light-hole and heavy-hole transitions allowed the determination of both the superlattice band gap and the valence-band offset. The offset was found to be 300 meV (±20 meV) for the superlattices studied, which extrapolates to 350 meV (±20 meV) for the HgTe–CdTe binary interface.