Abstract

We report on the effects of changing the surface densities of MOVPE-grown free-standing GaAs-AlGaAs core-shellnanowires on the resulting nanostructure size and their photoluminescence (PL) properties. It is demonstrated thatdecreasing the local density of GaAs nanowires within the array leads to an increase of the overgrown AlGaAs shellthickness and to a substantial redshift of the nanostructure excitonic emission. Application of a vapor mass-transportlimited growth model of the AlGaAs shell allows explaining the dependence of shell growth rate on nanowire density.The observed redshift of the nanowire PL emission is then experimentally correlated with these density-induced changesof the nanostructure size, namely with the nanowire shell-thickness to core-radius ratio hs/Rc. To account for a possiblecontribution of the nanostructure built-in elastic strain to the energy shift of the peak excitonic emission, the strain fieldin present core-shell nanowires was calculated as function of the nanostructure relevant geometrical parameters, based ona uniaxial elastic energy equilibrium model, and its effect on valence and conduction band shifts of the GaAs coreevaluated by means of the Pikus-Bir Hamiltonian. Good agreement is obtained for hs/Rc<1, the strain-free excitonicemission being identified at 1.510 eV and ascribed to bound heavy-hole excitons. For hs/Rc>1 increasingly largerredshifts (up to ~9 meV in excess of values calculated based on the elastic strain model) are observed, and tentativelyascribed to shell-dependent exciton localization effects.

Autore Pugliese

• Prete Paola

Tutti gli autori

• P. Prete; I. Miccoli I.; N. Lovergine

Titolo volume/Rivista

Proceedings of SPIE

Anno di pubblicazione

2014

ISSN

1996-756X

ISBN

Non Disponibile

Numero di citazioni Wos

Nessuna citazione

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Numero di citazioni Scopus

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Settori ERC

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Codici ASJC

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