Spatially resolved ultrafast transport current in GaAs photoswitches

TL;DR

This study uses a pump-probe scheme to analyze ultrafast transport currents in GaAs photoswitches, revealing collective electron-hole plasma dynamics with velocities surpassing single-particle limits.

Contribution

It demonstrates the dominance of collective plasma effects in ultrafast transport currents, providing new insights into carrier dynamics in GaAs photoswitches.

Findings

Displacement current pulse observed as previously reported.

Transport current velocity exceeds Fermi and quantum velocities.

Collective electron-hole plasma excitation dominates ultrafast transport.

Abstract

We apply a pump- and probe-scheme to coplanar stripline circuits to investigate the photocurrent response of GaAs photoswitches in time and space. We find a displacement current pulse, as has been reported earlier. A time-delayed second pulse is interpreted by a transport current. A time-of-flight analysis allows us to determine the velocity of the photogenerated charge carriers in the transport current. It exceeds the Fermi and the single-particle quantum velocities. This suggests that the excitation of a collective electron-hole plasma and not single charge-carriers dominates the ultrafast transport current in GaAs photoswitches.