Results are presented on the composition and temperature dependence of the luminescence in plasma deposited amorphous SixC1-x alloys using films of composition ranging from pure Si to 90% C in the 77 K to 450 K temperature range. There is evidence to suggest that the radiative recombination rate increases by over a factor of 103 from pure Si to C rich films. This increase is shown to be also consistent with the composition dependence of the quantum efficiency. These results are discussed in terms of a radiative tunnelling model