Selective Area Growth of GaAs Nanowires and Microplatelet Arrays on Silicon by Hydride Vapor-Phase Epitaxy

In this work, we demonstrate the growth of vertically oriented GaAs nanowires (NWs) and microplatelets directly on a patterned SiO2/Si(111) substrate by hydride vapor-phase epitaxy (HVPE). Direct condensation of GaAs on Si was achieved through a critical surface preparation under an As-controlled atmosphere. GaAs NWs were grown along the ⟨111⟩B direction with a hexagonal cross section when the hole opening diameter (D) in the SiO2 mask was below 350 nm. Larger apertures (D ≥ 500 nm) resulted in uniform microplatelets. This study highlights the capability of HVPE for selective area growth of GaAs directly on Si and thus the potential of HVPE as a generic heterointegration process for III-V semiconductors on silicon.</p

Long indium-rich InGaAs nanowires by SAG-HVPE

International audienceAbstract We demonstrate the selective area growth of InGaAs nanowires (NWs) on GaAs (111)B substrates using hydride vapor phase epitaxy (HVPE). A high growth rate of more than 50 μ m h −1 and high aspect ratio NWs were obtained. Composition along the NWs was investigated by energy dispersive x-ray spectroscopy giving an average indium composition of 84%. This is consistent with the composition of 78% estimated from the photoluminescence spectrum of the NWs. Crystal structure analysis of the NWs by transmission electron microscopy indicated random stacking faults related to zinc-blende/wurtzite polytypism. This work demonstrates the ability of HVPE for growing high aspect ratio InGaAs NW arrays

Long catalyst-free InAs nanowires grown on silicon by HVPE

International audienceWe report for the first time on the hydride vapor phase epitaxy (HVPE) growth of long (26 μm) InAs nanowires on Si(111) substrate grown at a standard rate of 50 μm h−1. The nanowires grow vertically along the (111)B direction and exhibit a well faceted hexagonal shape with a constant diameter. The effect of the experimental parameters, growth temperature and III/V ratio, is investigated. The thermodynamic and kinetic mechanisms involved during the growth of such long nanowires are identified. It is demonstrated that growth occurs through direct condensation of InCl and As4/As2 gaseous species. Dechlorination of adsorbed InCl molecules is the limiting step at low temperature. Structural analysis through high resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field (HAADF) imaging was performed. The high As4 partial pressure of the HVPE environment induces the presence of both wurtzite and zinc-blende phases. The results emphasize the potential of the low cost HVPE technique for the monolithic integration of arrays of long InAs nanowires on silicon

Dynamics of Gold Droplet Formation on SiO 2 /Si(111) Surface

International audienceAu droplets are used as a catalyst for the growth of nanowires on Si(111) substrate via the vapor-liquid-solid (VLS) mechanism. The dewetting of a Au thin film is the most common method to obtain these droplets. The control of this step is crucial to adjust the density and the diameter of the nanowires during VLS growth. When the Si(111) substrate is covered with a silicon dioxide layer, the kinetics of Au droplet formation is strongly modified. The dependence of the diameter and spatial distribution of the droplets on the surface have been studied by scanning electron microscopy with respect to the thickness of the silicon dioxide layer, the thickness of the Au film and the temperature of the substrate during deposition and post-deposition annealing. In-situ low energy electron microscopy and low energy electron diffraction revealed the dynamics of the Au droplet formation after annealing. The Au droplets are shown to catalyze the decomposition of silicon dioxide at high temperature (> 650-700 °C) and form a wetting layer of Au-(33)-Si(111). Consequently, the droplets absorb silicon atoms from the substrate, migrate perpendicular to the atomic steps and grow by the Smoluchowski ripening process

Importance of As and Ga Balance in Achieving Long GaAs Nanowires by Selective Area Epitaxy

We report on the selective area growth (SAG) of GaAs nanowires (NWs) by the catalyst-free vapor-solid mechanism. Well-ordered GaAs NWs were grown on GaAs(111)B substrates patterned with a dielectric mask using hydride vapor phase epitaxy (HVPE). GaAs NWs were grown along the ⟨111⟩B direction with perfect hexagonal shape when the hole’s opening diameter in SiNx or SiOx mask was varied from 80 to 340 nm. The impact of growth conditions and the hole size on the NW lengths and growth rates was investigated. A saturation of the NW lengths was observed at high partial pressures of As4, explained by the presence of As trimers on the (111)B surface at the NW top surface. By decreasing As4 partial pressure and decreasing the hole size, high aspect ratio NWs were obtained. The longest and thinnest NWs grew faster than a two-dimensional layer under the same conditions, which strongly suggests that surface diffusion of Ga adatoms from the NW sidewalls to their top contributes to the resulting axial growth rate. These findings were supported by a dedicated model. The study highlights the capability of the HVPE process to grow high aspect ratio GaAs NW arrays with high selectivity.</p

Selective Area Growth by Hydride Vapor Phase Epitaxy and Optical Properties of InAs Nanowire Arrays

International audienceWe report on the selective area growth of InAs nanowires (NWs) by the catalyst-free vapor−solid method. Well-ordered InAs NWs were grown on GaAs(111)B and Si(111) substrates patterned with a dielectric mask using hydride vapor phase epitaxy (HVPE). Vertical and high aspect ratio InAs NWs with a hexagonal shape were grown on both GaAs and Si substrates. The impact of the growth conditions on the InAs morphology was investigated. The final shape of the InAs crystal was tuned from a NW to a nanoplatelet by controlling growth conditions such as growth temperature, vapor phase composition, and mask pattern. The influence of the aperture size on the nucleation density and then on the morphology of InAs is discussed. Small openings resulted in the formation of a single nucleus per hole, which was then converted to a NW. For larger apertures, the number of nuclei increased, leading to both three-dimensional crystals and NWs. The effect of growth temperature and the III/V ratio on the kinetics and thermodynamics of InAs growth is also discussed. The growth was first optimized on a GaAs(111)B substrate and then performed on Si, which is more suitable to develop devices. Finally, the absorbance and photoluminescence measurements were carried out on the InAs NW arrays, demonstrating the high potential of HVPE-grown InAs NWs for future multispectral photo-detection devices

Perpendicular shape anisotropy spin transfer torque-MRAM: Determination of pillar tilt angle from 3D Stoner Wohlfarth astroid analysis

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Selective Area Growth of GaAs Nanowires and Microplatelet Arrays on Silicon by Hydride Vapor-Phase Epitaxy

In this work, we demonstrate the growth of vertically oriented GaAs nanowires (NWs) and microplatelets directly on a patterned SiO2/Si(111) substrate by hydride vapor-phase epitaxy (HVPE). Direct condensation of GaAs on Si was achieved through a critical surface preparation under an As-controlled atmosphere. GaAs NWs were grown along the ⟨111⟩B direction with a hexagonal cross section when the hole opening diameter (D) in the SiO2 mask was below 350 nm. Larger apertures (D ≥ 500 nm) resulted in uniform microplatelets. This study highlights the capability of HVPE for selective area growth of GaAs directly on Si and thus the potential of HVPE as a generic heterointegration process for III-V semiconductors on silicon.</p