Ratchet effects in quantum wells with a lateral superlattice

Experimental and theoretical work on the ratchet effects in quantum wells with a lateral superlattice excited by alternating electric fields of terahertz frequency range is reviewed. We discuss the Seebeck ratchet effect and a helicity driven photocurrents and show that the photocurrent generation is based on the combined action of a spatially periodic in-plane potential and a spatially modulated light.