1 research outputs found
Direct Determination of Minority Carrier Diffusion Lengths at Axial GaAs Nanowire p–n Junctions
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