The consequences of a positive substrate bias applied during the molecular beam epitaxial growth of Si/SiGe multiple quantum well (MQW) structures have been investigated, by studying the photoluminescence (PL) properties of as-grown and rapid thermal annealed samples. Strain relaxation by diffusion mechanisms results in an annealed-induced energy shift of the excitonic bandgap luminescence line. This shift is found to be dependent on the growth bias. Transmission electron microscopy measurements on the MQWs reveal a correlation between the defect density and the shape of the PL spectra, with well-resolved phonon signals and small defect concentrations under the conditions of positive substrate bias and/or subsequent anneals. Our studies provide further insights into the nature of grown-in defects in Si and SiGe films caused by ions generated during electron gun evaporation.