Dynamics of local photoconductivity in GaAs and InP investigated by THz SNOM

TL;DR

This study uses THz-SNOM to investigate the ultrafast evolution of photoconductivity in GaAs and InP, revealing different decay mechanisms and proposing analysis strategies for near-field spectra.

Contribution

It introduces a novel application of THz-SNOM to study ultrafast photoconductivity dynamics in semiconductors, highlighting different decay processes in GaAs and InP.

Findings

InP photoconductivity decay is mainly due to electron diffusion and surface band-bending effects.

GaAs exhibits different ultrafast photoconductivity dynamics compared to InP.

The paper proposes strategies for analyzing THz-SNOM signals and estimates measurement accuracy.

Abstract

Terahertz scanning near-field optical microscope (THz-SNOM) is employed to measure ultrafast evolution of THz conductivity spectra after photoexcitation of GaAs and InP wafers using ultrashort laser pulses. Unlike in GaAs, the THz photoconductivity decay in InP is controlled mainly by the diffusion of electrons away from the photoexcited area, and also by the drift due to band-bending at the surface of the semiconductor. We propose and discuss several general strategies of the analysis of signals measured using THz-SNOM, and we estimate the accuracy of the obtained near-field photoconductivity spectra.