title: Excitonic Diffusion in InGaN/GaN Core-Shell Nanowires.
abstract: We report on the direct observation of the diffusion of carriers in graded InGaN/GaN quantum wells in a nanowire. By probing the local dynamics at the nanoscale, along the wire for different temperatures between 4 and 250 K, we conclude that this diffusion process is thermally activated. In addition, the analysis of the cathodoluminescence lifetime for different temperatures shows that the carrier motion is isotropic and does not follow the indium gradient. Our observations are interpreted in terms of a hopping process between localized states. We find that the random alloy fluctuations prevent any directional drift of excitons along the In gradient and therefore any carrier accumulation. Our results therefore confirm the potential of core-shell nanowires for lighting devices. Indeed, the short lifetime of m-plane quantum wells together with their large active area and the homogeneous distribution of carrier along the quantum well will decrease influence of any high carrier density effect on the efficiency of these light-emitting diodes.
authors.affiliation: Laboratory of Quantum Optoelectronics, Ecole Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Shahmohammadi
authors.affiliation: Laboratory of Quantum Optoelectronics, Ecole Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland.
authors.forename: J-D
authors.initials: JD
authors.lastname: Ganière
authors.affiliation: Institut d'Electronique Fondamentale, UMR 8622 CNRS, Université Paris-Saclay , 91405 Orsay cedex, France.
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.affiliation: GLO AB , Ideon Science Park, Scheelevägen 17, S-223 70 Lund, Sweden.
authors.forename: R
authors.initials: R
authors.lastname: Ciechonski
authors.affiliation: GLO AB , Ideon Science Park, Scheelevägen 17, S-223 70 Lund, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Vescovi
authors.affiliation: GLO-USA , 1225 Bordeaux Drive, Sunnyvale, California 94086, United States.
authors.forename: O
authors.initials: O
authors.lastname: Kryliouk
authors.affiliation: Institut d'Electronique Fondamentale, UMR 8622 CNRS, Université Paris-Saclay , 91405 Orsay cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Tchernycheva
authors.affiliation: Laboratory of Quantum Optoelectronics, Ecole Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Jacopin
keywords: Cathodoluminescence; LED; core−shell nanowire; exciton hopping; localization