Low-temperature electron-spin relaxation is studied by the optical orientation method in bulk n-GaAs with donor concentrations from 10 14 cm Ϫ3 to 5ϫ10 17 cm Ϫ3 . A peculiarity related to the metal-to-insulator transition is observed in the dependence of the spin lifetime on doping near n D ϭ2ϫ10 16 cm Ϫ3 . In the metallic phase, spin relaxation is governed by the Dyakonov-Perel mechanism, while in the insulator phase it is due to anisotropic exchange interaction and hyperfine interaction

Strained GaSb quantum dots having a staggered band lineup (type II) are formed in a GaAs matrix using molecular beam epitaxy. The dots are growing in a self-organized way on a GaAs(100) surface upon deposition of 1.2 nm GaSb followed by a GaAs cap layer. Plan-view transmission electron microscopy studies reveal well developed rectangular-shaped GaSb islands with a lateral extension of ∼20 nm. Intense photoluminescence (PL) is observed at an energy lower than the GaSb wetting layer luminescence. This line is attributed to radiative recombination of 0D holes located in the GaSb dots and electrons located in the surrounding regions. The GaSb quantum dot PL dominates the spectrum up to high excitation densities and up to room temperature.

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We report on molecular beam epitaxial growth of InSb submonolayer insertions in an InAs matrix, exhibiting intense mid-IR photoluminescence (PL) up to room temperature (RT). The InSb insertions are fabricated by an exposure of InAs surface to an antimony Sb4 flux. The nominal thickness of insertions grown at different temperatures (TS=400–485°C) ranges from 0.6 to 1.4 monolayer, as estimated from x-ray diffraction measurements of InSb∕InAs multiple submonolayer structures. This gives rise to the variation of the emission wavelength within the 3.9–4.3 μm range at RT. An integral PL intensity drop from 77 K to RT does not exceed 20 times.