Filtered ultraviolet (UV) light was used to desorb impurities present at the growth front of aluminium nitride prepared by remote plasma enhanced chemical vapour deposition at room temperature. Trimethylaluminium and trimethylamine alane were used as metalorganics. Unfiltered ultraviolet light from a mercury arc lamp was found to inhibit film growth entirely; a glass plate with a short wavelength 10% transmission cutoff of 330 nm was therefore used as a UV filter. Substantial improvements in the insulating properties of the AlN films were observed for films grown with the filtered UV light present. Improvements in film morphology and an increase in breakdown fields were also observed. Further experiments with pyrex filtered UV light with a short wavelength 10% transmission cutoff of 283 nm were carried out, though better results were achieved with glass filtering.