Terahertz magneto-spectroscopy of transient plasmas in semiconductors

TL;DR

This study uses synchronized NIR and THz lasers to perform time-resolved spectroscopy of transient plasmas in semiconductors, revealing carrier dynamics and the dominant scattering mechanisms, with notable magnetic field effects in InSb.

Contribution

It introduces a combined experimental and theoretical approach to analyze transient plasma dynamics in semiconductors under magnetic fields, highlighting electron-electron scattering as dominant.

Findings

Electron-electron scattering dominates scattering time.

Magnetic field significantly affects InSb plasma dynamics.

Theoretical model accurately reproduces experimental plasma evolution.

Abstract

Using synchronized near-infrared (NIR) and terahertz (THz) lasers, we have performed picosecond time-resolved THz spectroscopy of transient carriers in semiconductors. Specifically, we measured the temporal evolution of THz transmission and reflectivity after NIR excitation. We systematically investigated transient carrier relaxation in GaAs and InSb with varying NIR intensities and magnetic fields. Using this information, we were able to determine the evolution of the THz absorption to study the dynamics of photocreated carriers. We developed a theory based on a Drude conductivity with time-dependent density and density-dependent scattering lifetime, which successfully reproduced the observed plasma dynamics. Detailed comparison between experimental and theoretical results revealed a linear dependence of the scattering frequency on density, which suggests that electron-electron scattering is the dominant scattering mechanism for determining the scattering time. In InSb, plasma dynamics was dramatically modified by the application of a magnetic field, showing rich magneto-reflection spectra, while GaAs did not show any significant magnetic field dependence. We attribute this to the small effective masses of the carriers in InSb compared to GaAs, which made the plasma, cyclotron, and photon energies all comparable in the density, magnetic field, and wavelength ranges of the current study.