ELECTROREFLECTANCE SPECTRA OF GEXSI1-X SI STRAINED-LAYER MULTIPLE-QUANTUM WELLS/

We have investigated the optical transitions above the fundamental gap of a set of GexSi1-x/Si strained layer Multiple-quantum wells by elec troreflectance (ER). The samples were grown by molecular beam espitaxy (MBE). The thickness of the strained layer of GexSi1-x was 5nm with G e concentration x in the range from 0.4 to 0.5, and the Si barrier lay er greater than 16nm. Considering the energy shift caused by strain an d quantum well confinement, we were able to clearly recognize the tran sitions from different quantum well structures associated with the cri tical points E0, E0', and E1. The transitions of the critical points E 0 and E0', which are very weak in bulk materials, are apparently enhan ced in the quantum well structures.