The effect of alloying and expitaxial mismatch strain on the surface ultraviolet (UV) emission efficiencies of AlxGa1-xN films, pseudomorphically grown on both c- and m-plane AlyGa1-yN templates (x < y) for various Al-content combinations, has been investigated under the framework of k.p perturbation theory. The results indicate that the film/template Al-content combination with y >-0.03 + 1.79x-0.06x(2) (0 < x < y < 1) for the c-plane case and the film/template with all y:x (0 < x < y < 1) combinations for the m-plane case, are particularly suitable for obtaining efficient UV light emissions. In the latter case, it's also ideal for fabricating edge-emitting UV devices with predominant transverse electric mode. Furthermore, polarized emissions with high polarization degree can be achieved by properly tuning the y:x ratio for certain x. (C) 2011 Elsevier B.V. All rights reserved.