Influence of growth conditions on the formation of deep photoluminescence bands in MBE-grown Si layers and SiGe/Si quantum structures

Influence of the growth parameters, i.e. growth temperature and ion bombardment, on the quality of SiGe/Si quantum structures and Si thin films, grown by molecular beam epitaxy (MBE), is studied using photoluminescence (PL) spectroscopy, optically detected cyclotron resonance and high-resolution X-ray diffraction measurements. The bombardment of even a low flux of Si+ ions, as present in the MBE growth with biased substrates, is shown to degrade essentially the quality of epitaxial structures due to creation of both point-like and extended defects. The low temperature MBE growth primarily results in a quenching of SiGe-related emissions relative to the substrate-related PL due to formation of competing non-radiative channels associated, presumably, with vacancy-type complex defects.