title: Determination of the Optimal Shell Thickness for Self-Catalyzed GaAs/AlGaAs Core-Shell Nanowires on Silicon.
abstract: We present a set of experimental results showing a combination of various effects, that is, surface recombination velocity, surface charge traps, strain, and structural defects, that govern the carrier dynamics of self-catalyzed GaAs/AlGaAs core-shell nanowires (NWs) grown on a Si(111) substrate by molecular beam epitaxy. Time-resolved photoluminescence of NW ensemble and spatially resolved cathodoluminescence of single NWs reveal that emission intensity, decay time, and carrier diffusion length of the GaAs NW core strongly depend on the AlGaAs shell thickness but in a nonmonotonic fashion. Although 7 nm AlGaAs shell can efficiently suppress the surface recombination velocity of the GaAs NW core, the influence of the surface charge traps and the strain between the core and the shell that redshift the luminescence of the GaAs NW core remain observable in the whole range of the shell thickness. In addition, the band bending effect induced by the surface charge traps can alter the scattering of the excess carriers inside the GaAs NW core at the core/shell interface. If the AlGaAs shell thickness is larger than 50 nm, the luminescence efficiency of the GaAs NW cores deteriorates, ascribed to defect formation inside the AlGaAs shell evidenced by transmission electron microscopy.
authors.affiliation: Université Grenoble Alpes , F-38000, Grenoble, France.|Nanophysique et Semiconducteurs Group, CNRS, Institut Néel , F-38000, Grenoble, France.
authors.forename: R
authors.initials: R
authors.lastname: Songmuang
authors.affiliation: Université Grenoble Alpes , F-38000, Grenoble, France.|Nanophysique et Semiconducteurs Group, CNRS, Institut Néel , F-38000, Grenoble, France.
authors.forename: Le Thuy Thanh
authors.initials: le TT
authors.lastname: Giang
authors.affiliation: Université Grenoble Alpes , F-38000, Grenoble, France.|Nanophysique et Semiconducteurs Group, CEA, INAC-SP2M , F-38000, Grenoble, France.
authors.forename: J
authors.initials: J
authors.lastname: Bleuse
authors.affiliation: Université Grenoble Alpes , F-38000, Grenoble, France.|Nanophysique et Semiconducteurs Group, CNRS, Institut Néel , F-38000, Grenoble, France.
authors.forename: M
authors.initials: M
authors.lastname: Den Hertog
authors.affiliation: Université Grenoble Alpes , F-38000, Grenoble, France.|Laboratoire de Simulation Atomistique, CEA, INAC-SP2M , F-38000, Grenoble, France.
authors.forename: Y M
authors.initials: YM
authors.lastname: Niquet
authors.affiliation: Université Grenoble Alpes , F-38000, Grenoble, France.|Nanophysique et Semiconducteurs Group, CNRS, Institut Néel , F-38000, Grenoble, France.
authors.forename: Le Si
authors.initials: le S
authors.lastname: Dang
authors.affiliation: Université Grenoble Alpes , F-38000, Grenoble, France.|Nanophysique et Semiconducteurs Group, CNRS, Institut Néel , F-38000, Grenoble, France.
authors.forename: H
authors.initials: H
authors.lastname: Mariette
keywords: Core−shell nanowires; III−As semiconductors; luminescence; surface charges; surface passivation