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Quantum dots (QDs) formed on GaAs(100) substrates by InAs deposition followed by (Al,Ga)As or (In,Ga,Al)As overgrowth demonstrate a photoluminescence (PL) peak that is redshifted (up to 1.3 μm) compared to PL emission of GaAs-covered QDs. The result is attributed to redistribution of InAs molecules in the system in favor of the QDs, stimulated by Al atoms in the cap layer. The deposition of a 1 nm thick AlAs cover layer on top of the InAs-GaAs QDs results in replacement of InAs molecules of the wetting layer by AlAs molecules, leading to a significant increase in the heights of the InAs QDs, as follows from transmission electron microscopy. This effect is directly confirmed by transmission electron microscopy indicating a transition to a Volmer-Weber-like QD arrangement. We demonstrate an injection laser based on this kind of QDs. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The influence of different growth conditions on the In distribution in ultrathin InGaN insertions in a GaN matrix is investigated by high-resolution transmission electron microscopy and an appropriate image evaluation technique. It is demonstrated that the indium distribution represents dense arrays of In-rich nanodomains inserted in a layer with a lower indium concentration. The sizes of the In-rich regions are about 4-5 nm at a growth temperature of 720 °C. Increasing the growth temperature leads to a strong decrease in the of nanoisland density and, also, a moderate decrease in their lateral size. Increasing the trimethylindium/trimethylgallium ratio strongly increases the density of the islands, but the lateral size remains weakly effected. The observations are in agreement with a thermodynamic model of island formation including entropy effects. [ABSTRACT FROM AUTHOR]

InAs self-organized quantum dots in In[sub 0.53]Ga[sub 0.47]As and In[sub 0.52]Al[sub 0.48]As matrices have been grown on InP substrates by molecular beam epitaxy. The dot size in InGaAs has been found to be 3–4 times larger, but the areal density about an order of magnitude smaller than that in InAlAs. Low-temperature photoluminescence (PL) of the InAs/InGaAs quantum dots is characterized by a narrow (35 meV) PL line as compared to that of InAs/InAlAs quantum dots (170 meV). Quantum dot formation increases the carrier localization energy as compared to quantum well structures with the same InAs thickness in a similar manner for both InAs/InGaAs and InAs/InAlAs structures. The effect of the barrier band gap on the optical transition energy is qualitatively the same for quantum well and quantum dot structures. The results demonstrate a possibility of controlling the quantum dot emission wavelength by varying the matrix composition. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]