The effect of interface potential fluctuations of a Si/SiGe multiple quantum well structure upon the low temperature exciton luminescence is studied. A possible exciton localization at such potential fluctuations, with a lateral period of 9-12 nm, is observed as a blue shift with increasing excitation power in the low temperature photoluminescence. Moreover, annealing the sample at temperatures well below the growth temperature leads to the formation of striations with a period of several micrometers along the 011 direction. To clarify whether or not a metallic decoration of misfit dislocations is needed to observe D1-line photoluminescence (PL) emission, annealing was performed in two different ways. Only in the case of annealing in direct contact with a metal, D1-line emission was observed in photoluminescence experiments.