EVIDENCE FOR INTERFACE TERRACES IN GE SI QUANTUM-WELLS OBTAINED BY RAMAN-SCATTERING/

We show that the change of the laser energy induces a frequency shift and broadening of the Ge-Ge resonant Raman line in Ge5Si5/Si QWs. This is explained by the existence of interfacial terraces, a conclusion s upported by the study of QWs of different multiplicities: (i) The Ge-S i line broadens with QW multiplicity suggesting a wider distribution o f terraces with increasing number of QWs. (ii) The Ge-Ge vibration is confined and does not propagate into the Si barrier, its line width an d frequency depends on the QW width and therefore on the QWs multiplic ity, (iii) The number of QWs affects the confined electronic states.