Ultralow Surface Recombination
Velocity in InP Nanowires
Probed by Terahertz Spectroscopy
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Abstract
Using transient terahertz photoconductivity measurements,
we have
made noncontact, room temperature measurements of the ultrafast charge
carrier dynamics in InP nanowires. InP nanowires exhibited a very
long photoconductivity lifetime of over 1 ns, and carrier lifetimes
were remarkably insensitive to surface states despite the large nanowire
surface area-to-volume ratio. An exceptionally low surface recombination
velocity (170 cm/s) was recorded at room temperature. These results
suggest that InP nanowires are prime candidates for optoelectronic
devices, particularly photovoltaic devices, without the need for surface
passivation. We found that the carrier mobility is not limited by
nanowire diameter but is strongly limited by the presence of planar
crystallographic defects such as stacking faults in these predominantly
wurtzite nanowires. These findings show the great potential of very
narrow InP nanowires for electronic devices but indicate that improvements
in the crystallographic uniformity of InP nanowires will be critical
for future nanowire device engineering