title: Direct determination of minority carrier diffusion lengths at axial GaAs nanowire p-n junctions.
abstract: Axial GaAs nanowire p-n diodes, possibly one of the core elements of future nanowire solar cells and light emitters, were grown via the Au-assisted vapor-liquid-solid mode, contacted by electron beam lithography, and investigated using electron beam induced current measurements. The minority carrier diffusion lengths and dynamics of both, electrons and holes, were determined directly at the vicinity of the p-n junction. The generated photocurrent shows an exponential decay on both sides of the junction and the extracted diffusion lengths are about 1 order of magnitude lower compared to bulk material due to surface recombination. Moreover, the observed strong diameter-dependence is well in line with the surface-to-volume ratio of semiconductor nanowires. Estimating the surface recombination velocities clearly indicates a nonabrupt p-n junction, which is in essential agreement with the model of delayed dopant incorporation in the Au-assisted vapor-liquid-solid mechanism. Surface passivation using ammonium sulfide effectively reduces the surface recombination and thus leads to higher minority carrier diffusion lengths.
authors.affiliation: Solid State Electronics Department and CeNIDE, University of Duisburg-Essen, Lotharstrasse 55, 47048 Duisburg, Germany. christoph.gutsche@uni-due.de
authors.forename: Christoph
authors.initials: C
authors.lastname: Gutsche
authors.forename: Raphael
authors.initials: R
authors.lastname: Niepelt
authors.forename: Martin
authors.initials: M
authors.lastname: Gnauck
authors.forename: Andrey
authors.initials: A
authors.lastname: Lysov
authors.forename: Werner
authors.initials: W
authors.lastname: Prost
authors.forename: Carsten
authors.initials: C
authors.lastname: Ronning
authors.forename: Franz-Josef
authors.initials: FJ
authors.lastname: Tegude
mesh_terms: D001152:Arsenicals / Q000737:chemistry*; D003198:Computer Simulation; D004058:Diffusion; D004579:Electron Transport; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005708:Gallium / Q000737:chemistry*; D008422:Materials Testing; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D012666:Semiconductors
chemical_list: D001152:Arsenicals; C043055:gallium arsenide; D005708:Gallium