title: Crystal phase induced bandgap modifications in AlAs nanowires probed by resonant Raman spectroscopy.
abstract: We report on a major modification of the fundamental electronic band structure of AlAs when grown as a nanoscaled wurtzite crystal. Resonant Raman spectra of individual AlAs-GaAs core-shell nanowires display a resonance between 1.83 and 2.18 eV for the AlAs E₁(TO) phonon mode. Our findings substantiate the lowest conduction band of wurtzite AlAs to comprise Γ₈ symmetry and a low effective mass in agreement with calculations reported recently. The electronic resonance falls below the X, L, and Γ valleys known for AlAs in the zincblende phase. This result points toward a direct nature of wurtzite AlAs and is expected to apply more generally to semiconductors that in the bulk phase exhibit L valleys at lower energies than the conduction band at the Γ point.
authors.affiliation: Walter Schottky Institut and Physik Department, Technische Universität München , D-85748 Garching, Germany. stefan.funk@wsi.tum.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Funk
authors.forename: Ang
authors.initials: A
authors.lastname: Li
authors.forename: Daniele
authors.initials: D
authors.lastname: Ercolani
authors.forename: Mauro
authors.initials: M
authors.lastname: Gemmi
authors.forename: Lucia
authors.initials: L
authors.lastname: Sorba
authors.forename: Ilaria
authors.initials: I
authors.lastname: Zardo