Ultrafast Optical-Pump Terahertz-Probe Spectroscopy of the Carrier Relaxation and Recombination Dynamics in Epitaxial Graphene

TL;DR

This study uses ultrafast optical-pump Terahertz-probe spectroscopy to investigate the rapid carrier relaxation and recombination processes in epitaxial graphene, revealing sub-picosecond cooling and density-dependent recombination times.

Contribution

First measurement of electron-hole recombination times in epitaxial graphene using time-resolved Terahertz spectroscopy.

Findings

Carrier cooling occurs on sub-picosecond timescales.

Interband recombination times depend on carrier density.

Provides new insights into ultrafast carrier dynamics in graphene.

Abstract

The ultrafast relaxation and recombination dynamics of photogenerated electrons and holes in epitaxial graphene are studied using optical-pump Terahertz-probe spectroscopy. The conductivity in graphene at Terahertz frequencies depends on the carrier concentration as well as the carrier distribution in energy. Time-resolved studies of the conductivity can therefore be used to probe the dynamics associated with carrier intraband relaxation and interband recombination. We report the electron-hole recombination times in epitaxial graphene for the first time. Our results show that carrier cooling occurs on sub-picosecond time scales and that interband recombination times are carrier density dependent.