You’ll probably want to change your alpha channel to straight before rendering from maya.
In render settings on the maya software tab, under render options > colour / compositing uncheck the ‘premultiply’ box. That should fix it.
If you’re using some other renderer then i’m not sure of the exact method but you’ll probably have to do something similar.
If you dont want to re render from maya you might be able to just change the settings in after effects for the alpha channel to premultiplied with black, but if you’ve got any semi transparent areas then it probably wont look like you want it to.