What is it about?

Group III–V compound semiconductor nanowires with radial modulation of the materials composition and/or doping in the form of core–shell and core–multishell nanowire heterostructures show promise as novel and high-performance nano-scale light emitting diodes, lasers, photodetectors and solar cells. We report the experimental dependence of AlGaAs shell growth by metalorganic vapor phase epitaxy (MOVPE) around free-standing Au-catalysed GaAs nanowires on the relevant sizes and densities of the nanostructures. A model based on (i) the vapor mass transport of group III species, and (ii) perfect conformality between the nanowires and the substrate of AlGaAs deposition is proposed and validated.

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Why is it important?

A vapor mass-transport model was proposed, describing the MOVPE growth dynamics of the shell material around ensembles of GaAs nanowires, and validated by means of a detailed quantitative analysis of the nanostructure relevant size (diameters and heights of as-grown core–shell nanowires, Au catalyst nanoparticle size at their tips). We predict the complex (non-linear) dependence of the shell growth rate on the initial GaAs nanowire diameters (i.e., initial Au catalyst nanoparticle size), heights, local densities on the substrate, and deposition time, which is in very good agreement with experimental data; in particular, a monotonic decrease of AlGaAs shell thickness is expected and observed with increasing nanowire density.

Perspectives

I hope this work can help the scientific community working in the field to increase their knowledge about the nanowire heterostructures. Indeed, the presented results constitute a significant step towards the understanding of the MOVPE growth dynamics of group III–V compound materials around dense free-standing nanowire ensembles, and for the controlled fabrication of radially modulated (i.e., core–shell and core–multishell) nanowire heterostructures with stringent/predictable compositional/dopant profile characteristics.

Dr. Paola Prete
Consiglio Nazionale delle Ricerche

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This page is a summary of: Mass-transport driven growth dynamics of AlGaAs shells deposited around dense GaAs nanowires by metalorganic vapor phase epitaxy, CrystEngComm, January 2015, Royal Society of Chemistry, DOI: 10.1039/c5ce00980d.
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