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High-quality InGaAsP/InP multi-quantum wells (MQWs) on the isolated areas of indium phosphide on silicon necessary for realizing a monolithically integrated silicon laser is achieved. Indium phosphide layer on silicon, the pre-requisite for the growth of quantum wells is achieved via nano-epitaxial lateral overgrowth (NELOG) technique from a defective seed indium phosphide layer on silicon. This technique makes use of epitaxial lateral overgrowth (ELOG) from closely spaced (1 μm) e-beam lithography-patterned nano-sized openings (~300 nm) by low-pressure hydride vapor phase epitaxy. A silicon dioxide mask with carefully designed opening patterns and thickness with respect to the opening width is used to block the defects propagating from the indium phosphide seed layer by the so-called necking effect. Growth conditions are optimized to obtain smooth surface morphology even after coalescence of laterally grown indium phosphide from adjacent openings. Surface morphology and optical properties of the NELOG indium phosphide layer are studied using atomic force microscopy, cathodoluminescence and room temperature μ-photoluminescence (μ-PL) measurements. Metal organic vapor phase epitaxial growth of InGaAsP/InP MQWs on the NELOG indium phosphide is conducted. The mask patterns to avoid loading effect that can cause excessive well/barrier thickness and composition change with respect to the targeted values is optimized. Cross-sectional transmission electron microscope studies show that the coalesced NELOG InP on Si is defect-free. PL measurement results indicate the good material quality of the grown MQWs. Microdisk (MD) cavities are fabricated from the MQWs on ELOG layer. PL spectra reveal the existence of resonant modes arising out of these MD cavities. A mode solver using finite difference method indicates the pertinent steps that should be adopted to realize lasing. [ABSTRACT FROM AUTHOR]

It is demonstrated that the growth direction of InP nanowires grown on (001)-oriented silicon substrate strongly depends on the diameter of the gold catalyst droplets. Small droplets with diameter less than about 15 nm lead to the formation of nanowires leaning on the {111} planes of the zinc blende InP seeds formed in the early stages of growth. Larger droplets lead to the formation of twins in the InP seeds and to the formation of nanowires leaning on the {111} planes of these twinned InP variants, inducing growth directions corresponding to the <115> directions of the silicon substrate. [ABSTRACT FROM AUTHOR]

Whereas resonant transverse magnetic transmission across an undulated continuous metal film is achieved with the mediation of plasmon modes excited by the undulation, it is shown here that transverse electric (TE) resonant transmission through a continuous metal film can also be achieved with the mediation of the second-order TE mode of a dielectric slab waveguide having the metal film sandwiched at its middle. The demonstration is made by using the materials currently used in the domain of optical security and counterfeit deterrence: ZnS is shown to possibly be a lossless interface/adhesion layer between a polymer and a noble metal for plasmonic resonant elements. [ABSTRACT FROM AUTHOR]

A ZnO planar optical microcavity displaying room-temperature polariton lasing over a wide range of cavity-exciton detunings has been fabricated. The cavity combines optimum crystalline quality, given by a ZnO single-crystal substrate, and optimum photonic quality, obtained by the use of two dielectric SiO2/HfO2 Bragg mirrors. A maximum cavity quality factor of about 4000 has been measured. Typically, the polariton lasing transition is accompanied by an increase of the output intensity by more than two orders of magnitude, a reduction of the emission linewidth and a relatively small blueshift of the lower polariton branch (less than 5% of the Rabi splitting). [ABSTRACT FROM AUTHOR]

A chemical reaction, derived from an ancient recipe for hair dyeing, is used to precipitate nanoparticles of mercury sulphide in hair by the simple process of immersion in a water solution of Ca(OH)2and HgO. After several days, HgS nanoparticles appear throughout the hair and are particularly numerous in the various interfaces. The formation of these nanoparticles has been studied by analytical and atomic resolution electron microscopy. High resolution quantitative analysis allowed the determination of two varieties of HgS precipitate crystal structures formed: a hexagonal cinnabar and a cubic metacinnabar structure. This very simple process of a chemical reaction in hair is a particularly inexpensive way to fabricate semiconductor sulphide nanoparticles with specific properties. [ABSTRACT FROM AUTHOR]

The kinetics of the growth of GaN crystalline nanowires on a Si (111) surface with no catalyst is studied experimentally and theoretically. Noncatalytic GaN nanowires were grown by molecular-beam epitaxy with AlN inserts, which makes it possible to determine the rate of the vertical growth of nanowires. A model for the formation of GaN nanowires is developed, and an expression for their rate of growth is derived. It is shown that, in the general case, the dependence of the rate of growth on the nanowire diameter has a minimum. The diameter corresponding to the experimentally observed minimum of the rate of growth steadily increases with increasing diffusion flux from the lateral surface. [ABSTRACT FROM AUTHOR]

The effect of the postgrowth annealing of InP/InAsP/InP heterostructural nanowires produced by molecular-beam epitaxy on their structural and optical properties is studied. It is shown that the procedure of short-term (1 min) annealing in an argon atmosphere provides a means for increasing the emission intensity of InAsP quantum dots, suppressing the emission from InAsP quantum wells formed as a result of lateral growth, and substantially reducing the density of structural defects in the nanowires. [ABSTRACT FROM AUTHOR]

Highly reflective deep UV distributed Bragg reflectors (DBRs) based on the BAlN material system have been grown by metalorganic vapour phase epitaxy on AlN template substrates. These structures make use of the transparency of BAlN in the deep UV and the high refractive index contrast between BAlN and AlN, which has been demonstrated to exceed 0.27 at 280 nm. 18-pair BAlN/AlN DBRs showed experimental peak reflectivity of 82% at 311 nm and a stop-bandwidth of 20 nm. At 282 nm, a 24-pair BAlN/AlN DBR structure is demonstrated with experimental peak reflectivity of 60% and stop-bandwidth of 16 nm. [ABSTRACT FROM AUTHOR]

InP nanowires grown on silicon substrate are investigated using time-resolved spectroscopy. A strong modification of the exciton lifetime is observed (from 0.11 to 1.2 ns) when the growth temperature is increased from 340 °C to 460 °C. This strong dependence is not related to the density of zinc-blende insertions in the wurtzite nanowires or to the wurtzite exciton linewidth. The excitation power dependence of the lifetime and linewidth is investigated, and these results allow us to interpret the growth temperature dependence on the lifetime as a consequence of the reduction of the surface recombination velocity with the growth temperature. [ABSTRACT FROM AUTHOR]

Abstract: Compositionally modulated GaP/GaAs1−x P x nanowires are grown by molecular beam epitaxy in the vapor liquid solid mode using Au as catalyst. By periodically supplying As, we achieve atomically flat and abrupt interfaces along the whole length of the nanowires. This is a step towards the realization of superlattices in nanowires. [Copyright &y& Elsevier]

A new SiH4/Cl2 chemistry is proposed for the high-aspect-ratio etching of InP-based heterostructures. Anisotropic etching is obtained through the deposition of a SiOx passivation layer on the etched sidewalls. SiH4 has been chosen as a single precursor for both Si and H species that are necessary to promote the passivation process. Previously developed Cl2/H2- or HBr-based chemistries for anisotropic etching of laser waveguides or vertical microcavities require a silicon wafer below the InP samples in order to assist the passivation mechanism. In contrast, the authors show that a SiOx passivation can be achieved and maintained almost independent of the nature of the wafer surface when SiH4 is added. This is of practical importance for the processing of III-V wafers having the same size as the electrode or for III-V heterogeneous integration when III-V dies bonded onto a 200/300 mm diameter wafer have to be etched. Smooth, notch-free, anisotropic etching of InGa(Al)As/InP heterostructures is demonstrated. Ex situ energy-dispersive x-ray spectroscopy coupled to a transmission electron microscope is used to analyze the composition of the thin passivation layer deposited on the sidewalls of etched features. The authors show that the passivation layer consists of a Si-rich silicon oxide (Si/O∼1) in Cl2/H2/SiH4 chemistry and is changed to nanocrystalline Si in SiH4/Cl2 chemistry depending on the SiH4 concentration in the feed gas. An aspect ratio as high as 28 is obtained in the latter case. [ABSTRACT FROM AUTHOR]

Abstract: BGaN ternary alloys with 0.7% and 1.7% boron grown on GaN/sapphire template substrates by metalorganic vapour phase epitaxy (MOVPE) have been investigated through HAADF-STEM. At low boron content, 0.7%, no compositional fluctuations were observed with XRD or STEM measurements. Photoluminescence at room temperature was measured. At higher boron content, cubic BGaN nano-sized clusters were identified. The clusters are 3nm wide, homogeneously distributed in size and in density and coherent with the surrounding wurtzite BGaN matrix. Their boron composition was estimated by EDX. [Copyright &y& Elsevier]

Abstract: Nanodots, nanowires, and semi-polar quantum well structures of GaN-based material have been grown by nano-selective area growth (NSAG). The growth evolution of the nanostructure has been studied. Cross-sectional transmission electron microscopy (TEM) shows that the nanostructures are free of threading dislocations. The growth of AlGaN/GaN layers is uniform and shows sharp interfaces between the AlGaN and GaN epilayers. AlGaN nanodots/nanowires, which are formed at the apexes of the nano-pyramids/nano-ridges, are found to be homogeneous in size and to have a higher aluminum mole fraction than the surrounding material. In contrast, the InGaN/GaN growth shows no quantum dots at the apexes of the nanostructures. We found that the growth facets of different Miller’s indices are formed on the InGaN/GaN nano-ridges. Energy dispersive X-ray spectroscopy (EDX) shows higher indium incorporation at the intersection of the growth facets. Cathodoluminescence measurements show enhanced luminescence intensity from InGaN multi-quantum wells (MQWs) grown on the nanostructure compared to that from InGaN MQWs grown on an unpatterned area. [Copyright &y& Elsevier]