Affiliation: | a GHMFL, CNRS, BP 166, F-38042, Grenoble Cedex 9, France b INSA, 135 Avenue de Rangueil, F-31077, Toulouse Cedex 4, France c Institute of Semiconductor Physics, Novosibirsk 630090, Russia d Institut Universitaire de France, 103 Bd. St. Michel, F-75005, Paris, France e CEA/LETI, F-38054, Grenoble Cedex 9, France f University College, London WC 15 75, United Kingdom |