Ultrafast magneto-photocurrents in GaAs: Separation of surface and bulk contributions

TL;DR

This study demonstrates ultrafast magneto-photocurrents in GaAs, separating surface and bulk effects using terahertz emission measurements, revealing different microscopic origins including the inverse Spin-Hall effect.

Contribution

It introduces a non-invasive method to distinguish surface and bulk magneto-photocurrents in GaAs via terahertz emission analysis at room temperature.

Findings

Surface and bulk contributions are separable by sample orientation.

Different excitation intensities and photon energies affect the currents.

Inverse Spin-Hall effect is involved in the microscopic origins.

Abstract

We induce ultrafast magneto-photocurrents in a GaAs crystal employing interband excitation with femtosecond laser pulses at room temperature and non-invasively separate surface and bulk contributions to the overall current response. The separation between the different symmetry contributions is achieved by measuring the simultaneously emitted terahertz radiation for different sample orientations. Excitation intensity and photon energy dependences of the magneto-photocurrents for linearly and circularly polarized excitations reveal an involvement of different microscopic origins, one of which we believe is the inverse Spin-Hall effect. Our experiments are important for a better understanding of the complex momentum-space carrier dynamics in magnetic fields.