Direct ultraviolet excitation of an amorphous AlN:praseodymium phosphor by codoped Gd3+ cathodoluminescence

Sputter deposited thin film amorphous AlN:Pr (1 at. %) emits in the blue-green (490-530 nm) and red (similar to 650 nm) regions of the visible spectrum under electron excitation. The addition of Gd 1 at. % in the film enhances the blue emission by an order of magnitude. The enhancement in the blue region is a result of cathodoluminescence from Gd3+ at 313 nm. The optical bandgap of amorphous AlN is about 210 nm, so that the film is transparent in the ultraviolet, allowing the Gd emission to excite the Pr3+ ions. No significant quenching of the Gd emission is observed when the Gd and Pr ions are mixed. The blue enhancement is observed even with the two films containing each of the ions that are separated by a 500 mu m thick quartz spacer, showing that the enhancement is due entirely to UV radiation.