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A two-steps wet-etching fabrication process producing high-quality GaAs microdisks is presented. We report an optical characterization of these microdisks, using the photoluminescence of InAs quantum boxes as an internal light source. Thanks to an improved smoothness of the microdisk sidewall, cavity Q’s as high as 12 000 are observed, which opens very challenging novel application prospects for semiconductor microdisks.

We investigate cavity-quantum electrodynamics ͑QED͒ effects in an all-semiconductor nanostructure by tuning a single self-assembled InAs quantum dot ͑QD͒ into resonance with a high quality factor microdisk whispering gallery mode ͑WGM͒. The stronger temperature dependence of the QD single-exciton ͑1X͒ resonance allows us to change the relative energy of the WGM and the 1X transitions by varying the sample temperature. The two coupled resonances exhibit crossing behavior due to the weak coupling cavity-QED regime. We demonstrate exciton lifetime reduction by 6 due to the Purcell effect by tuning the QD into resonance with the WGM. Our experiments also show that single-exciton lifetime is independent of temperature up to 50 K.

This paper reports on the growth, structural and optical properties of GaN free-stranding nanowires synthesized in catalyst-free mode on Si(111) substrate by plasma-assisted molecular beam epitaxy. Cylindrical nanowires with a hexagonal cross-section defined by {1010} planes and diameters down to 20 nm were observed. The nanowire length increases as a function of their diameter, following the Gibbs-Thomson expression. The growth rate in the lateral direction was studied using thin AlN marker layers showing that the lateral over axial growth rate ratio can be tuned from ∼1% to ∼10% by changing the III/V flux ratio, with the lateral growth remaining homogeneous along the NW axis. Nanowire ensembles showed a strong near band edge photoluminescence up to room temperature. Low-temperature micro-photoluminescence from a single wire is peaked at 3.478 eV with broadening of 6-10 meV. This emission is similar to the luminescence of nanowire ensembles, which demonstrates strain homogeneity from wire to wire. The optical properties along the wire axis probed by micro-cathodoluminescence were found to be uniform, with no evidence of a higher defect density in the bottom part of the nanowires next to the Si substrate.