title: Pressure tuning of the optical properties of GaAs nanowires.
abstract: The tuning of the optical and electronic properties of semiconductor nanowires can be achieved by crystal phase engineering. Zinc-blende and diamond semiconductors exhibit pressure-induced structural transitions as well as a strong pressure dependence of the band gaps. When reduced to nanoscale dimensions, new phenomena may appear. We demonstrate the tuning of the optical properties of GaAs nanowires and the induction of a phase transition by applying an external pressure. The dependence of the E(0) gap on the applied pressure was measured, and a direct-to-indirect transition was found. Resonant Raman scattering was obtained by pressure tuning of the E(0) and the E(0) + Δ(SO) gaps with respect to the excitation energy. The resonances of the longitudinal optical modes LO and 2LO indicate the presence of electron-phonon Fröhlich interactions. These measurements show for the first time a variation of ionicity in GaAs when in nanowire form. Furthermore, the dependence of the lattice constant on applied pressure was estimated. Finally, we found a clear indication of a structural transition above 16 GPa.
authors.affiliation: Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, D-85748 Garching, Germany. ilaria.zardo@wsi.tum.de
authors.forename: Ilaria
authors.initials: I
authors.lastname: Zardo
authors.forename: Sara
authors.initials: S
authors.lastname: Yazji
authors.forename: Carlo
authors.initials: C
authors.lastname: Marini
authors.forename: Emanuele
authors.initials: E
authors.lastname: Uccelli
authors.forename: Anna
authors.initials: A
authors.lastname: Fontcuberta i Morral
authors.forename: Gerhard
authors.initials: G
authors.lastname: Abstreiter
authors.forename: Paolo
authors.initials: P
authors.lastname: Postorino