Classical ratchet effects in heterostructures with a lateral periodic potential

TL;DR

This paper investigates terahertz-induced ratchet currents in semiconductor heterostructures with a lateral periodic potential, revealing polarization-independent and dependent effects driven by the superlattice and electromagnetic interactions.

Contribution

It demonstrates the existence of polarization-sensitive ratchet effects in low-dimensional structures with lateral superlattices, extending the class of ratchet systems to include linear and circular polarization sensitivities.

Findings

Seebeck ratchet effect significantly contributes to photocurrent.

Polarization-dependent photocurrents are observed and microscopically explained.

Lateral superlattices enable new polarization-sensitive ratchet mechanisms.

Abstract

We study terahertz radiation induced ratchet currents in low dimensional semiconductor structures with a superimposed one-dimensional lateral periodic potential. The periodic potential is produced by etching a grating into the sample surface or depositing metal stripes periodically on the sample top. Microscopically, the photocurrent generation is based on the combined action of the lateral periodic potential, verified by transport measurements, and the in-plane modulated pumping caused by the lateral superlattice. We show that a substantial part of the total current is caused by the polarization-independent Seebeck ratchet effect. In addition, polarization-dependent photocurrents occur, which we interpret in terms of their underlying microscopical mechanisms. As a result, the class of ratchet systems needs to be extended by linear and circular ratchets, sensitive to linear and circular polarizations of the driving electro-magnetic force.