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Carrier relaxation and recombination in self-organized InAs/GaAs quantum dots ͑QD's͒ is investigated by photoluminescence ͑PL͒, PL excitation ͑PLE͒, and time-resolved PL spectroscopy. We demonstrate inelastic phonon scattering to be the dominant intradot carrier-relaxation mechanism. Multiphonon processes involving up to four LO phonons from either the InAs QD's, the InAs wetting layer, or the GaAs barrier are resolved. The observation of multiphonon resonances in the PLE spectra of the QD's is discussed in analogy to hot exciton relaxation in higher-dimensional semiconductor systems and proposed to be intricately bound to the inhomogeneity of the QD ensemble in conjunction with a competing nonradiative recombination channel observed for the excited hole states. Carrier capture is found to be a cascade process with the initial capture into excited states taking less than a few picoseconds and the multiphonon ͑involving three LO phonons͒ relaxation time of the first excited hole state being 40 ps. The ͉001͘ hole state presents a relaxation bottleneck that determines the ground-state population time after nonresonant excitation. For the small self-organized InAs/GaAs QD's the intradot carrier relaxation is shown to be faster than radiative ͑Ͼ1 ns͒ and nonradiative ͑Ϸ100 ps͒ recombination explaining the absence of a ''phonon bottleneck'' effect in the PL spectra. ͓S0163-1829͑97͒09340-5͔

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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.

InAs self-organized quantum dots inserted in InGaAs quantum well have been grown on GaAs substrates by molecular beam epitaxy. The lateral size of the InAs islands has been found to be approximately 1.5 times larger as compared to the InAs/GaAs case, whereas the island heights and surface densities were close in both cases. The quantum dot emission wavelength can be controllably changed from 1.1 to 1.3 μm by varying the composition of the InGaAs quantum well matrix. Photoluminescence at 1.33 μm from vertical optical microcavities containing the InAs/InGaAs quantum dot array was demonstrated.