Liquid phase epitaxial layers of InxGa1−xAsyP1−y grown lattice matched to InP〈001〉 substrates, in the concentration range 0.53⩽x⩽0.88, have been studied by transmission electron microscopy. For the usual growth temperatures, solid instability was predicted for compositions in the range 0.55≲x≲0.75. Indeed a quasiperiodic variation of a strain contrast, though very light in some cases, is always observed in the 〈100〉 and 〈010〉 directions in that composition range, and never outside. The pseudoperiodicity is of the order of 1000 Å. Local concentration measurements have been performed on one sample using a scanning transmission electron microscope. They show that the strain contrast, quite strong in that sample, is related to a concentration modulation. The measured variations on x and y are as high as 0.1, and they keep the ratio x/y constant, which is consistent with phase separation observed on nucleated InxGa1−xAsyP1−y.

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We have studied the photoluminescence of ZnSe doped by diffusion of Al at high temperature (1000–1100 °C) or by Ga at low temperature (600 °C). The diffused samples are highly conductive (0.1<ρ<10 Ω cm). According to the doping conditions the luminescence, at 300 °K, is dominated by the well-known self-activated orange emission (6300 Å) or by a yellow-green band that we assign to Na-Al complexes. Annealing in zinc atmosphere was found to have a large influence on the photoluminescence of the Ga-doped samples only. Thus, at 300 °K, the annealed samples exhibit a blue intrinsic emission with a strong reduction of the orange or the yellow-green bands; at 77 and 4.2 °K the photoluminescence spectra are dominated by blue lines corresponding, respectively, to free-electron–acceptor or donor-acceptor recombinations. We show that the shallow acceptor involved is Na.

An investigation of the crystalline and optical properties of AlInAs as a function of the molecular-beam epitaxial growth conditions is reported. The surface reconstruction phases diagram has been established. We show the possibility of growing this material with smooth surface under (Al-In)-stabilized (4×2) reconstructed surface. Such layers present a specific photoluminescence behavior; transmission electron microscopy observations suggest the existence of spinodal decomposition. Films grown under usual (2×4) surface show 2-K photoluminescence peak as narrow as 16 meV (FWHM), but we found that no correlation may be established a priori between the optical and crystalline properties. A high silicon doping study is also reported. We show the segregation and accumulation of Si toward the surface at high level.