Well, photons are bosons (spin 1 not 1/2) as result they have very different statistics. You can get population inversion (e.g. a laser or bose condensate) wher

Well, photons are bosons (spin 1 not 1/2) as result they have very different statistics. You can get population inversion (e.g. a laser or bose condensate) where many of the bosons all sit in a single energy level. That's not possible for fermions due to the fermi exclusion principal (e.g. electron orbital shells).