Imaging Charge Separation and Carrier Recombination
in Nanowire p‑i‑n Junctions Using Ultrafast Microscopy
- Publication date
- Publisher
Abstract
Silicon nanowires incorporating p-type/n-type
(p-n) junctions have
been introduced as basic building blocks for future nanoscale electronic
components. Controlling charge flow through these doped nanostructures
is central to their function, yet our understanding of this process
is inferred from measurements that average over entire structures
or integrate over long times. Here, we have used femtosecond pump–probe
microscopy to directly image the dynamics of photogenerated charge
carriers in silicon nanowires encoded with p-n junctions along the
growth axis. Initially, motion is dictated by carrier–carrier
interactions, resulting in diffusive spreading of the neutral electron–hole
cloud. Charge separation occurs at longer times as the carrier distribution
reaches the edges of the depletion region, leading to a persistent
electron population in the n-type region. Time-resolved visualization
of the carrier dynamics yields clear, direct information on fundamental
drift, diffusion, and recombination processes in these systems, providing
a powerful tool for understanding and improving materials for nanotechnology