The localization of excitons on quantum-dot-like compositional fluctuations has been observed in temperature-dependent near-field magnetophotoluminescence spectra of InGaAsN. Localization is driven by the giant bowing parameter of these alloys and manifests itself by the appearance of ultranarrow lines (half-width <1 meV) at temperatures below 70 K. We show how near-field optical scanning microscopy can be used for the estimation of the size, density, and nitrogen excess of individual compositional fluctuations (clusters), thus revealing random versus phase-separation effects in the distribution of nitrogen.

Raman spectra of coherently strained layers of GaAs 1Ϫx N x grown on ͑001͒ GaAs with xϭ0 -0.05 by metalorganic molecular-beam epitaxy are reported. The optical phonons of the GaAs and GaN types, as well as disorder-activated acoustical phonons, are observed. A strongly confined GaAs optical mode at ϳ255 cm Ϫ1 , indicating the ordering of As and N atoms, is also detected. The GaAs-and GaN-type optical phonons exhibit strong diagonal components, forbidden for the zinc-blende structure. A bond polarizability analysis of the Raman selection rules shows that these components are activated by the trigonal distortion of the alloy lattice. The trigonal distortion arises from the formation of ordered ͕111͖-(GaN) m (GaAs) n clusters with nϭmϭ1.

We study the optical properties of MoS2 nanotubes (NTs) with walls comprising dozens of monolayers. We reveal strong peaks in micro-photoluminescence (μ-PL) spectra when detecting the light polarized along the NT axis. We develop a model describing the optical properties of the nanotubes acting as optical resonators which support the quantization of whispering gallery modes inside the NT wall. The experimental observation of the resonances in μ-PL allows one to use them as a contactless method of the estimation of the wall width. Our findings open a way to use such NTs as polarization-sensitive components of nanophotonic devices.

A mechanically induced solid-state reaction method for the synthesis of organic-inorganic hybrid perovskites, such as methylammonium lead iodide (CH 3 NH 3 PbI 3 ) is reported. The perovskites were synthesized both in bulk and Al 2 O 3 -supported forms. The phase-and structural-formation mechanisms of such perovskites are also investigated. The experiments suggest that diffusion of PbI 2 into CH 3 NH 3 I crystals is a rate-limiting step of the reaction process. It is also shown that water (humidity) significantly influences the reaction kinetics. UV-Vis-NIR absorption and photoluminescence spectroscopies indicate that the band edge and emission characteristics of the as-fabricated materials strongly depend on their particle size.

We report on the growth of ZnSnP2 on GaAs(100) substrates by gas source molecular beam epitaxy. Samples were grown in the temperature range of 300–360 °C. A small change in the Sn/Zn flux ratio at constant substrate temperature was found to result in a transition from a lattice mismatched, Δa/a∼0.4%–0.7%, disordered crystal structure to a lattice matched, ordered chalcopyrite structure. Infrared reflectance and Raman measurements were used to monitor this phase transition. Formation of the two different crystal modifications is discussed in terms of vapor–solid and vapor–liquid–solid growth modes.

Articles you may be interested inHigh-electron-mobility GaN grown on free-standing GaN templates by ammonia-based molecular beam epitaxy J. Appl. Phys. 115, 193702 (2014); 10.1063/1.4874735 N-type conductivity and properties of carbon-doped InN(0001) films grown by molecular beam epitaxy J. Appl. Phys. 113, 033501 (2013); 10.1063/1.4775736Improved electron mobility in InSb epilayers and quantum wells on off-axis Ge (001) substrates The authors report the structural, optical, and transport properties of high quality InN epitaxial films grown on GaN substrates by plasma-assisted molecular beam epitaxy. They have found a strong correlation between the structural quality and the measured carrier mobilities. Comparison of temperature-dependent Hall data with a theoretical transport model indicates that the electron mobility in state-of-art InN is limited by charged dislocation scattering. The model predicts that an order-of-magnitude increase in electron mobilities can be achieved by the reduction of dislocation densities in InN.

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Mechanism for improvements of optical properties of 1.3-μ m InAs ∕ GaAs quantum dots by a combined InAlAs -InGaAs cap layer J. Appl. Phys. 98, 083516 (2005); 10.1063/1.2113408 Tuning InAs/GaAs quantum dot properties under Stranski-Krastanov growth mode for 1.3 μm applicationsSuppression of temperature sensitivity of interband emission energy in 1.3-μm-region by an InGaAs overgrowth on self-assembled InGaAs/GaAs quantum dots Quantum dots ͑QDs͒ formed on GaAs͑100͒ substrates by InAs deposition followed by ͑Al,Ga͒As or ͑In,Ga,Al͒As overgrowth demonstrate a photoluminescence ͑PL͒ peak that is redshifted ͑up to 1.3 m͒ 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.