Photoluminescence study of Si/SiGe multiple quantum wells grown by MBE

Pseudomorphic Si/SiGe multiple quantum well (MQW) structures were grown by solid source molecular beam epitaxy (MBE). The optical and structural properties of MQWs grown with and without bias applied to the substrate during the deposition were studied in detail, SiGe phonon resolved band-edge luminescence of as-grown samples is found only for MQWs deposited with a positive bias at the substrate. Subsequent rapid thermal annealing improves the photoluminescence properties of films grown with zero or positive bias, whereas for samples grown with a negative bias a broad deep luminescence band is observed. A strong correlation between the observation of the deep luminescence and thr appearance of defects in the SiGe layers is established. It is most likely that these defects originate from ion bombardment of the growing film during e-beam evaporation in solid source MBE.