Photovoltage induced by ratchet effect in Si/SiGe heterostructures under microwave irradiation

Directed electron transport induced by polarized microwave in Si/SiGe heterostructure is investigated by patterning an array of semicircular antidots in hexagonal geometry. Carriers interact strongly with the asymmetric antidots under microwave radiation and the broken spatial symmetry drives the carriers to move preferably in one direction (ratchet effect), thereby generating a longitudinal photovoltage. In addition to this, the strong electron-electron interaction in Si/SiGe heterostructure favors a collective carrier motion along the sample edges, which gives rise to the transverse photovoltage. Both longitudinal and transverse photovoltage induced by ratchet effect opens up promising possibilities for Si/SiGe based photogalvanic detectors. (C) 2011 American Institute of Physics. [doi:10.1063/1.3590255]