title: Radial Stark Effect in (In,Ga)N Nanowires.
abstract: We study the luminescence of unintentionally doped and Si-doped InxGa1-xN nanowires with a low In content (x < 0.2) grown by molecular beam epitaxy on Si substrates. The emission band observed at 300 K from the unintentionally doped samples is centered at much lower energies (800 meV) than expected from the In content measured by X-ray diffractometry and energy dispersive X-ray spectroscopy. This discrepancy arises from the pinning of the Fermi level at the sidewalls of the nanowires, which gives rise to strong radial built-in electric fields. The combination of the built-in electric fields with the compositional fluctuations inherent to (In,Ga)N alloys induces a competition between spatially direct and indirect recombination channels. At elevated temperatures, electrons at the core of the nanowire recombine with holes close to the surface, and the emission from unintentionally doped nanowires exhibits a Stark shift of several hundreds of meV. The competition between spatially direct and indirect transitions is analyzed as a function of temperature for samples with various Si concentrations. We propose that the radial Stark effect is responsible for the broadband absorption of (In,Ga)N nanowires across the entire visible range, which makes these nanostructures a promising platform for solar energy applications.
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Jonas
authors.initials: J
authors.lastname: Lähnemann
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Pierre
authors.initials: P
authors.lastname: Corfdir
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Feix
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Jumpei
authors.initials: J
authors.lastname: Kamimura
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Timur
authors.initials: T
authors.lastname: Flissikowski
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Holger T
authors.initials: HT
authors.lastname: Grahn
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Geelhaar
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Brandt
keywords: (In,Ga)N; Fermi level pinning; Stark effect; carrier localization; luminescence spectroscopy; nanowires