Ratchet effects induced by terahertz radiation in heterostructures with a lateral periodic potential

TL;DR

This paper demonstrates terahertz radiation can induce photogalvanic currents in semiconductor heterostructures with engineered lateral periodic potentials, revealing a new microscopical mechanism involving near-field effects and pattern asymmetry.

Contribution

It introduces a novel microscopical mechanism for polarization-dependent photogalvanic effects in heterostructures with lateral periodic potentials, supported by experimental and phenomenological analysis.

Findings

Photocurrents are induced by terahertz radiation in patterned heterostructures.

The lateral pattern asymmetry can be controlled to produce classical ratchets.

A new mechanism involving near-field effects explains the polarization dependence.

Abstract

We report on the observation of terahertz radiation induced photogalvanic currents in semiconductor heterostructures with one-dimensional lateral periodic potential. The potential is produced by etching a grating into the sample surface. The electric current response is well described by phenomenological theory including both the circular and linear photogalvanic effects. Experimental data demonstrate that the inversion asymmetry of the periodic lateral pattern can be varied by means of electron beam lithography to produce classical lateral ratchets. A novel microscopical mechanism for the polarization-dependent photogalvanic effects has been proposed to interpret the experimental findings. The photocurrent generation is based on the combined action of the lateral periodic potential and the modulated in-plane pumping. The latter modulation stems from near-field effects of the radiation propagating through the grating.