title: Local electric field enhancement at the heterojunction of Si/SiGe axially heterostructured nanowires under laser illumination.
abstract: We present a phenomenon concerning electromagnetic enhancement at the heterojunction region of axially heterostructured Si/SiGe nanowires when the nanowire is illuminated by a focused laser beam. The local electric field is sensed by micro Raman spectroscopy, which allows the enhancement of the Raman signal arising from the heterojunction region to be revealed; the Raman signal per unit volume increases at least ten times with respect to the homogeneous Si and SiGe nanowire segments. In order to explore the physical meaning of this phenomenon, a three-dimensional solution of the Maxwell equations of the interaction between the focused laser beam and the nanowire was carried out by finite element methods. A local enhancement of the electric field at the heterojunction was deduced. However, the magnitude of the electromagnetic field enhancement only approaches the experimental one when the free carriers are considered, showing enhanced absorption at the carrier depleted heterojunction region. The existence of this effect promises a way of improving photon harvesting using axially heterostructured semiconductor nanowires.
authors.affiliation: GdS Optronlab, Dpt. Física de la Materia Condensada, ed. i+d, Parque Científico, Universidad de Valladolid, Paseo de Belén 1, 47011 Valladolid, Spain.
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Pura
authors.forename: Julián
authors.initials: J
authors.lastname: Anaya
authors.forename: Jorge
authors.initials: J
authors.lastname: Souto
authors.forename: Ángel Carmelo
authors.initials: ÁC
authors.lastname: Prieto
authors.forename: Andrés
authors.initials: A
authors.lastname: Rodríguez
authors.forename: Tomás
authors.initials: T
authors.lastname: Rodríguez
authors.forename: Juan
authors.initials: J
authors.lastname: Jiménez