A series of PbTe/PbEuTe double barrier samples with different barrier widths were successfully grown on BaF2 substrates by molecular beam epitaxy. The electron concentration of PbTe spacer and well layers was controlled by the deviation from stoichiometry, while the buffer and cap layers were intentionally doped with bismuth to obtain low-resistivity layers to be used as top and bottom contacts. Assuming 50% of band offset, a barrier height of 150 meV was determined by infrared transmission measurements, corresponding to a PbEuTe barrier with 5% of europium content. The structural parameters of the samples were accurately determined by combining the measurement in a high-resolution x-ray diffractometer in the triple-axis configuration with a simulation within the framework of dynamical theory of diffraction.

A series of SnTe layers with thicknesses varying from 0.42 to 9.1 µm were grown by molecular beam epitaxy on (111) BaF2 substrates. The SnTe lattice parameter was found to be 6.331 Å as determined from x-ray diffraction spectra measured in the triple-axis configuration. The FWHM of the (222) SnTe x-ray rocking curves indicated a good crystalline quality and an unusual dependence on layer thickness. Atomic force microscopy (AFM) of the SnTe surface revealed spirals with monolayer steps formed around threading dislocations, similar to the PbTe on BaF2 epitaxy. The dislocation density was estimated from the AFM picture to be 9x10(8) cm-2. Small black pits corresponding to holes that were left during growth were also observed on the AFM images. Sn diffusion can be a possible reason for these pits and the relatively high dislocation density. Electrical measurements showed that the SnTe epilayers present a typical p-type carrier concentration around 10(20) cm- 3 almost temperature independent and a Hall mobility which decreases from 10(4) to 10³ cm²/V.s as the temperature increases from 10 to 350K.

PbTe mesa diodes were fabricated from a series of p - n junctions grown on BaF2 substrates. For this series, the hole concentration was kept constant at 10(17) cm-3 and the electron concentration varied between 10(17) and 10(19) cm-3. Capacitance versus voltage analysis revealed that for n > 10(18) cm-3, a one-sided abrupt junction is formed. The direct and reverse branches of the current versus voltage curves exhibited different forms among the diodes. The R0A product varied between 0.23 and 31.8 omegacm², and the integral detectivity ranged from 1.1x10(8) to 6.5x10(10) cmHz½W-1. The performance of the best PbTe photodiodes fabricated here is comparable to the commercial InSb and HgCdTe infrared detectors, and to the PbTe sensors grown on Si substrate.

Epilayers of Sn1-xEu xTe (0 < x < 0:03) were grown by molecular beam epitaxy on freshly cleaved BaF2(111) substrates and their structural, electrical and optical properties were investigated. The thicknesses of epilayers were about 1.5 mum and deposition was carried out at growth temperatures of 300 ºC. The structural properties were investigated by high resolution X-ray diffraction and a sharp film degradation could be observed with increasing europium content. Electrical measurements with temperature varying from 300 to 10K indicated that the epilayers present carrier concentration ranging between 3 x 10(20) and 6 x 10(20)cm-3 and a low resistivity from 6.3 x 10-5 to 1.2 x 10-4 omega.cm. From optical measurements it could be seen that spectra present a low energy edge corresponding to the beginning of intra band excitations and the high energy edge due to inter band excitations.

Using high quality epitaxial layers, we have obtained direct evidence of the band inversion in the Pb1-xSn xTe system .The samples, covering the whole composition range, were grown by molecular beam epitaxy on (111)BaF2 substrates. A minimumin the resistivity as a function of temperature was observed for all samples with Sn composition 0.35 <= x <= 0.70. In the same samples and at the same temperature, temperature dependent optical transmission measurements have revealed a change in signal of the energy gap temperature derivative, a direct evidence of the band inversion. However, the temperature for which the inversion occurs is not the one expected by the band inversion model. This discrepancy is supposed to be due to the Burstein-Moss shift caused by the relatively high hole concentration observed in these samples.