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Formation, emission, and lasing properties of strain-free InP(As)/AlInAs quantum dots (QDs) embedded in AlInAs microdisk (MD) cavity were investigated using transmission electron microscopy and photoluminescence (PL) techniques. In MD structures, the QDs have the nano-pan-cake shape with the height of ~2 nm, the lateral size of 20-50 nm, and the density of ~5×109 cm-2. Their emission observed at ~940 nm revealed strong temperature quenching, which points to exciton decomposition. It also showed unexpected type-I character, indicating In-As intermixing as confirmed by band structure calculations. We observed lasing of InP(As) QD excitons into whispering gallery modes in MD having the diameter of ~3.2 lm and providing a free spectral range of ~27 nm and quality factors up to Q~13 000. Threshold of ~50 W/cm2 and spontaneous emission coupling coefficient of ~0.2 were measured for this MD-QD system. [ABSTRACT FROM AUTHOR]

We used high-spatial-resolution, low-temperature near-field scanning optical microscopy (NSOM) operating at magnetic fields B=0-10T to study the effects of Wigner localization (WL) on emission spectra of single self-organized InP/GaInP quantum dots (QDs) and investigate the stability of singly (trion) and doubly (tetron) charged exciton complexes in the weak quantum confinement regime. Using NSOM measurements together with configuration interaction calculations, we identify the dots having different electron population N(N=1-12), quantum confinement (ℏω0=0.6-8meV) and size D(D=70-170nm). For N=2, we observed a magnetic-field-induced molecular-droplet transition, accompanied by the decomposition of the tetron into a Wigner molecule complex (WMC), and the activation of rotovibronic structure. For N=1, unusually strong vibronic structure resulting from a trion-type WMC was observed. We have shown that magnetic-field-induced shifts of this structure allow measurement of single particle Fock-Darwin levels and angular momentum transitions of the WMC. In addition, we demonstrated the use of NSOM imaging to probe the charge density distribution and observed anomalous dependence of the image size on the quantum confinement, implying a pairing of electrons or formation of whispering gallery modes in the QD. We demonstrated that InP/GaInP QDs, provide a Wigner-Seitz radius (rs) up to 13, and that the measurements of NSOM magneto-optical spectroscopy using these dots makes it possible to study effects arising from strong Coulomb interaction of a few confined electrons (holes). [ABSTRACT FROM AUTHOR]