We study the effect of different deposition conditions on properties In-polar InN grown by plasma-assisted molecular beam epitaxy. GaN buffer layers in Ga-droplet regime prior to significantly improved surface morphology films with excess In flux. Using this approach, have been realized room temperature electron mobilities as high 2250cm2∕Vs. correlate concentrations our unintentionally incorporated impurities, oxygen and hydrogen. A accumulation layer 5.11×1013cm−2 is measured for InN....

We investigated the interwire distance dependence on growth kinetics of vertical, high-yield InAs nanowire arrays Si(111) grown by catalyst-free selective area molecular beam epitaxy (MBE). Utilizing lithographically defined SiO2 nanomasks with regular hole patterns, and site-selective vertically (111)-oriented nanowires was achieved very high yields ∼90 percent. Interestingly, yield ordered independent initial stages. Significant size variation in found to depend critically time. Two...

We identify a new noncatalytic growth regime for molecular beam epitaxially grown GaAs nanowires (NWs) that may provide route toward axial heterostructures with discrete material boundaries and atomically sharp doping profiles. Upon increase of the As/Ga flux ratio, mode self-induced NWs on SiO(2)-masked Si(111) is found to exhibit surprising discontinuous transition in morphology aspect ratio. For effective ratios <1, situ reflection high-energy electron diffraction measurements reveal...

By employing various high-resolution metrology techniques we directly probe the material composition profile within GaAs-Al0.3Ga0.7As core-shell nanowires grown by molecular beam epitaxy on silicon. Micro Raman measurements performed along entire (>10 μm) length of [111]-oriented reveal excellent average compositional homogeneity nominally Al0.3Ga0.7As shell. In strong contrast, radial direction cross-sectional scanning transmission electron microscopy and associated chemical analysis rich...

Reliable technologies for the monolithic integration of lasers onto silicon represent holy grail chip-level optical interconnects. In this context, nanowires (NWs) fabricated using III-V semiconductors are strong interest since they can be grown site-selectively on conventional epitaxial approaches. Their unique one-dimensional structure and high refractive index naturally facilitate low loss waveguiding recirculation in active NW-core region. However, lasing from NWs has not been achieved...

III-As nanowires are candidates for near-infrared light emitters and detectors that can be directly integrated onto silicon. However, nanoscale to microscale variations in structure, composition, strain within a given nanowire, as well between nanowires, pose challenges correlating microstructure with device performance. In this work, we utilize coherent nanofocused X-rays characterize stacking defects single InGaAs nanowire supported on Si. By reconstructing diffraction patterns from the...

We investigated the role of temperature and In∕N flux ratios to determine suitable growth windows for plasma-assisted molecular beam epitaxy In-face (0001) InN. Under vacuum, InN starts decomposing at 435°C as defined by release N2 from crystal a buildup an In adlayer liquid droplets on sample surface. At temperatures greater than 470°C, decomposition was characterized both vapor in absence significant accumulation adlayer. No observed substrate above 500°C or which rates were higher rates....

We report self-induced growth of vertically aligned (i.e. along the [111] direction), free-standing InAs nanowires on Si(111) substrates by solid-source molecular beam epitaxy. Implementation an ultrathin amorphous SiO(x) mask facilitated epitaxial nanowire growth, as confirmed high-resolution x-ray diffraction 2theta-omega scans and transmission electron microscopy. Depending temperature (in range 400-520 degrees C) substantial size variation both length diameter was found under...

The authors demonstrate the impact of growth kinetics on surface and structural properties N-face InN grown by molecular beam epitaxy. Superior morphology with step-flow features is achieved consistently under In-rich conditions in a low-temperature region 500–540°C. Remarkably, off-axis x-ray rocking curve (ω scans) widths are found to be independent conditions. band gap determined from optical absorption measurements optimized 0.651eV, while photoluminescence peak emission occurs at even...

The thermal properties of freely suspended GaAs nanowires are investigated by applying a method which relies on laser heating and the determination local temperature Raman spectroscopy. In order to determine values for conductivity κ, fraction power absorbed inside nanowire is estimated numerical simulations. with homogeneous diameter found lie in range 8–36 W m−1 K−1. change profile presence tapering was investigated. Furthermore, we discuss influence ambient conditions value κ.

Thermal decomposition of wurtzite (0001)-oriented GaN was analyzed: in vacuum, under active N exposure, and during growth by rf plasma-assisted molecular beam epitaxy. The rate determined measurements the Ga desorption using situ quadrupole mass spectrometry, which showed Arrhenius behavior with an apparent activation energy 3.1 eV. Clear signatures intensity oscillations reflection high-energy electron diffraction facilitated complementary evaluation highlighted a layer-by-layer mode...

Abstract Free‐standing ternary InGaAs nanowires (NW) are at the core of intense investigations due to their integration capabilities on silicon (Si) for next‐generation photovoltaics, integrated photonics, tunneling devices, and high‐performance gate all‐round III–V/Si NW transistors. In this review, recent progress growth, structural, optical electrical properties NWs Si substrate is highlighted. Particular focus a comparison between conventional catalyst‐assisted catalyst‐free growth...

Utilizing narrow band gap nanowire (NW) materials to extend nanophotonic applications the mid-infrared spectral region (>2-3 μm) is highly attractive, however, progress has been seriously hampered due their poor radiative efficiencies arising from nonradiative surface and Auger recombination. Here, we demonstrate up ~ 10(2) times enhancements of emission intensities InAs NWs by growing an InAsP shell produce core-shell NWs. By systematically varying thickness phosphorus (P)-content shell,...

Surface effects strongly dominate the intrinsic properties of semiconductor nanowires (NWs), an observation that is commonly attributed to presence surface states and their modification electronic band structure. Although exposed, bare NW have been widely studied with respect charge carrier transport optical properties, underlying structure, Fermi level pinning, bending profiles are not well explored. Here, we directly quantitatively assess pinning at surfaces composition-tunable,...

Semiconductor nanowire (NW) lasers provide significant potential to create a new generation of and on-chip coherent light sources by virtue their ability operate as single mode optical waveguides at the nanoscale. Due unique geometry, major benefit lies also in feasibility for direct integration on silicon (Si), enabling III–V-on-Si NW that could fuel applications interconnects data communication. In this review, we describe state-of-the-art recent progress GaAs–AlGaAs based emitting near...

We demonstrate the growth and single-mode lasing operation of GaAs-AlGaAs core-multishell nanowires (NW) with radial single multiple GaAs quantum wells (QWs) as active gain media. When subject to optical pumping emission distinct s-shaped input-output characteristics, linewidth narrowing energies associated confined QWs are observed. Comparing low temperature performance QW NW laser structures having 7 coaxial a nominally identical structure only shows that threshold power density reduces...

III–V nanowire structures are among the promising material systems with applications in hot carrier solar cells. These nanostructures can meet requirements for such photovoltaic devices, i.e., suppression of thermalization loss, an efficient transport, and enhanced photoabsorption thanks to their unique one-dimensional (1D) geometry density-of-states. Here, we investigate effects spatial confinement photogenerated carriers InGaAs-InAlAs core–shell nanowires, which presents ideal class cell...

We present a Ga adsorption study of both polar GaN (0001) and $(0001\ifmmode\bar\else\textasciimacron\fi{})$ surfaces using line-of-sight quadrupole mass spectrometry as quantitative in situ method. Monitoring the desorbing atoms, two characteristic desorption regimes (exponential steady-state regimes) were found that are assigned to formation thin equilibrium adlayer droplets on top it. The coverage differs substantially between surface polarities, being 1.1 monolayers 2.4 GaN. Additional...

Real-time analysis of the growth modes during homoepitaxial (0001)GaN by plasma-assisted molecular beam epitaxy was performed using reflection high energy electron diffraction. A mode map established as a function Ga/N flux ratio and temperature, exhibiting distinct transitions between three-dimensional (3D), layer-by-layer step-flow mode. The to transition under Ga-rich surfactant mediated related Ga adlayer coverage one monolayer. Under N-rich conditions from 3D predominantly thermally...

The role of thermal instability and In surface coverages on the growth kinetics has been investigated for N-face InN films grown by plasma-assisted molecular beam epitaxy. Film thickness analysis using scanning electron microscopy combined with desorption measurements quadrupole mass spectrometry demonstrated significant decomposition starting at ∼560°C inhibiting completely beyond ∼635°C. Within this temperature region two pathways were identified: a low-temperature regime characterized...

We present combined in situ thermal cleaning and intentional doping strategies near the substrate regrowth interface to produce high-quality AlGaN/GaN high electron mobility transistors on semi-insulating (0001) GaN templates with low interfacial impurity concentrations buffer leakage. By exposing an optimized dissociation step plasma-assisted molecular beam epitaxy environment, oxygen, carbon, and, lesser extent, Si impurities were effectively removed from under preservation of good...

The threading dislocation (TD) structure and density has been studied in In- N-face InN films grown on GaN by plasma-assisted molecular beam epitaxy. TD densities were determined nondestructive x-ray diffraction rocking curve measurements on-axis symmetric off-axis skew geometries calibrated transmission electron microscopy measurements. dominated edge-type TDs with screw-component accounting for less than 10% of the total density. A significant decrease was observed In-face at increasingly...

The growth mechanism of self-induced InAs nanowires (NWs) grown on Si (111) by molecular beam epitaxy was investigated in situ reflection high energy electron diffraction and ex scanning transmission microscopy. Abrupt morphology transition in-plane strain relaxation revealed that NWs nucleate without any significant delay under the absence indium (In) droplets. These findings are independent As/In-flux ratio, revealing entirely linear vertical rate nontapered NWs. No evidence In droplets...

Temperature-dependent thermopower and Hall-effect measurements, combined with model calculations including all of the relevant elastic- inelastic-scattering mechanisms, are used to quantify role charged line defects on electron transport in $n$-type InN films grown by molecular-beam epitaxy. Films concentrations between $4\ifmmode\times\else\texttimes\fi{}{10}^{17}$ $5\ifmmode\times\else\texttimes\fi{}{10}^{19}$ cm${}^{\ensuremath{-}3}$ were investigated. Charged point defect scattering...