EFFECTS OF SUBSTRATE BIAS AND RAPID THERMAL-PROCESSING ON THE LUMINESCENCE OF SI SIGE MULTIPLE-QUANTUM WELLS GROWN BY MBE/

The consequences of a positive substrate bias applied during the molec ular beam epitaxial growth of Si/SiGe multiple quantum well (MQW) stru ctures have been investigated, by studying the photoluminescence (PL) properties of as-grown and rapid thermal annealed samples. Strain rela xation by diffusion mechanisms results in an annealed-induced energy s hift of the excitonic bandgap luminescence line. This shift is found t o be dependent on the growth bias. Transmission electron microscopy me asurements on the MQWs reveal a correlation between the defect density and the shape of the PL spectra, with well-resolved phonon signals an d small defect concentrations under the conditions of positive substra te bias and/or subsequent anneals. Our studies provide further insight s into the nature of grown-in defects in Si and SiGe films caused by i ons generated during electron gun evaporation.