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Abstract: Uniform layers of cadmium mercury telluride have been grown on inhomogeneous cadmium zinc telluride substrates by molecular beam epitaxy so that a single epitaxial layer experiences a laterally varying lattice mismatch. The lateral variations of layer and substrate lattice parameters, layer lattice tilt, diffraction peak width, etch pit density (EPD) and surface crosshatch have been characterized, and all measured quantities are reported as functions of the substrate lattice parameter. At small mismatch, the layer appears to be elastically deformed. Beyond a certain critical mismatch, the onset of relaxation is clearly observed in the layer lattice parameter. Relaxation leads to appearance of surface crosshatch and an increased diffraction peak width, but a reduction in EPD, suggesting a reduction in the density of threading dislocations within the layer.

Abstract: Interband magneto-absorption is used to characterize molecular beam epitaxially (MBE) grown HgCdTe epilayers. Both the bandgap and the Moss-Burstein shift in n-doped layers are determined from the experiments. A heterostructure sample consisting of four layers with different compositions is also analyzed. Due to the good experimental sensitivity all four bandgaps are determined, in contrast to optical transmission analysis without a magnetic field where only the lowest gap is readily visible. The interband magneto-absorption signal strongly depends on the electron mobility. This has been used as an aid to optimizing the MBE growth conditions of HgCdTe layers on different substrate orientations.

Cyclotron and intersubband resonances in HgTe quantum wells in the inverted band regime are studied by Fourier-transform spectroscopy. Metal-oxide-semiconductor field-effect transistors (MOSFETs) allow us to tune the electron density. In particular, we investigate filling factor dependent splittings of the cyclotron resonance in strong magnetic fields and a crossing of Landau levels of the conduction and valence subband. The experimental results are well described by a 6 × 6 k·p -model.

We have measured, by X-ray diffraction, the deformation of uniform cadmium mercury telluride layers epitaxially grown on cadmium zinc telluride substrates with varying zinc concentration. It is then possible, within the same sample, to clearly identify elastic deformation in the regions of small lattice mismatch and plastic deformation in the regions with larger mismatch. The deformation has been analysed in a framework based on a stress relaxation model published by Fontaine et al. This analysis permits determination of the energies of formation of misfit dislocations. They have been compared with values obtained from ab initio models. From this comparison possible relaxation mechanisms are proposed. A clear dissymmetry is also observed between relaxation of tensile and compressive strain. Pre-relaxation dislocation movements are also detected by diffraction peak broadening. Possible reasons for these behaviours are discussed.

The use of a magnetic field for interband absorption experiments in the midinfrared regime can reveal the electronic band structure of HgTe/CdTe superlattices. In high-quality samples pronounced magnetic field-induced absorption peaks are observed in the transmission spectra due to hole to electron Landau level transitions. By extrapolating the excitation energies for such transitions to B = 0, gap energies between several hole and electron subbands can be determined accurately. In addition, we show that interband magnetoabsorption provides a sensitive feedback for growth of quantum structures.