Direct Determination of Minority Carrier Diffusion Lengths at Axial GaAs Nanowire p-n Junctions

作者:Gutsche Christoph*; Niepelt Raphael; Gnauck Martin; Lysov Andrey; Prost Werner; Ronning Carsten; Tegude Franz Josef
来源:Nano Letters, 2012, 12(3): 1453-1458.
DOI:10.1021/nl204126n

摘要

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 I 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.

  • 出版日期2012-3