Near-band edge photoluminescence (PL) in high-quality tensile-strained Si type-II quantum wells (QWs) with varying well width grown on bulk crystal SiGe substrates by using ultrahigh vacuum chemical vapor deposition has been studied. In contrast to the blueshifts observed in the PL lines of Si1-xGex QWs on Si, the PL lines of Si QWs exhibit redshifts with increasing excitation density. The PL from the SiGe substrate shows no such shift. The excitation-induced PL redshifts decrease as the well width decreases, and are essentially independent of temperature up to 15 K. The rapid thermal annealing (RTA) was found to improve the crystal quality of the samples. RTA enhances the integrated PL intensity, results in narrowing and blueshifting of PL bands at a given excitation density, and reduces the exponent in the excitation power dependence as well as the amount of excitation-induced PL redshifting. Possible mechanisms for the observed excitation-induced PL redshifts were examined, including band bending, band filling, and binding of excitons to impurities. © 2003 American Institute of Physics.