Band-gap luminescence from Si1-xGex/Si heterostructures grown by Low Pressure Chemical Vapour Deposition (LPCVD) is studied for a composition range of x=.04 to x=.22 and thickness from l00nm to 1300nm. Special attention is paid to the influence of the growth conditions. The growth temperature was varied between 820°C and 600°C. We compare results obtained from our samples with results in the literature obtained from similar samples grown by other techniques, namely by molecular beam epitaxy (MBE). We show that with a growth temperature of 650°C we have achieved samples exhibiting a luminescence spectrum dominated by the excitonic recombination at the alloy, free from dislocation lines and defect related recombination. The dependence of the luminescence with Ge concentration and thickness of the alloy layer is well described by theory. Results for boron doped layers are also presented.