title: Investigation on localized states in GaN nanowires.
abstract: GaN nanowires with diameters ranging between 50 and 500 nm were investigated by electrical and photoinduced current techniques to determine the influence of their size on the opto-electronic behavior of nanodevices. The conductivity, photoconductivity, and persistent photoconductivity behavior of GaN nanowires are observed to strongly depend on the wire diameter. In particular, by spectral photoconductivity measurements, three main sub-band-gap optoelectronic transitions were detected, ascribed to the localized states giving rise to the characteristic blue, green, and yellow bands of GaN. Photoconductivity with below-band-gap excitation varies orders of magnitude with the wire diameter, similarly to that observed for near-band-edge excitation. Moreover, yellow-band-related signal shows a superlinear behavior with respect to the band-edge signal, offering new information for the modeling of the carrier recombination mechanism along the nanowires. The photoconductivity results agree well with a model which takes into account a uniform distribution of the localized states inside the wire and their direct recombination with the electrons in the conduction band.
authors.affiliation: CNISM and Physics Department, University of Bologna, V.le Berti-Pichat 6/2, 40127 Bologna, Italy. laura.polenta@unibo.it
authors.forename: L
authors.initials: L
authors.lastname: Polenta
authors.forename: M
authors.initials: M
authors.lastname: Rossi
authors.forename: A
authors.initials: A
authors.lastname: Cavallini
authors.forename: R
authors.initials: R
authors.lastname: Calarco
authors.forename: M
authors.initials: M
authors.lastname: Marso
authors.forename: R
authors.initials: R
authors.lastname: Meijers
authors.forename: T
authors.initials: T
authors.lastname: Richter
authors.forename: T
authors.initials: T
authors.lastname: Stoica
authors.forename: H
authors.initials: H
authors.lastname: Lüth
mesh_terms: D003460:Crystallization / Q000379:methods*; D004553:Electric Conductivity; D004563:Electrochemistry / Q000379:methods*; D005708:Gallium / Q000737:chemistry* / Q000528:radiation effects; D008027:Light; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D010777:Photochemistry / Q000379:methods*; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; C473348:gallium nitride; D005708:Gallium