Photoluminescence (PL) excitation and time-resolved PL measurements were conducted on erbium doped AlN. The Er:AlN film was grown by metal organic molecular beam epitaxy with a solid Er effusion source. The resulting Er concentration was 2–5×1019 Er/cm3. Photoluminescence excitation measurements revealed that Er3+ in Er:AlN can be excited either through direct optical pumping into Er3+ 4f levels or through an indirect carrier-mediated process. With respect to these two Er3+ excitation schemes, distinct Er3+ PL decay patterns were observed. The Er3+ PL excited by direct optical excitation was longer lived than that excited via a carrier-mediated process. Time-resolved PL measurements support that at least two classes of Er3+ PL centers exist in Er:AlN, and that direct optical excitation of Er3+ 4f levels primarily excites a set of longer-lived Er3+ sites which are not excited through carrier-mediated processes. © 1997 American Institute of Physics.