Structure changes of AlN:Ho films with annealing and enhancement of the Ho3+ emission

Abstract We have investigated the optical activity of Ho 3+ ions in AlN layers in the as prepared and annealed states. The films were grown using RF magnetron sputtering in a pure nitrogen atmosphere. After annealing we observe strong characteristic Ho 3+ emission peaks at 549, 660 and 760 nm corresponding to the 5 S 2 → 5 I 8 , 5 F 5 → 5 I 8 and 5 I 4 → 5 I 8 transitions, respectively. The emission peak at around 692 nm corresponds to the Cr 3+ emission (Cr is an unintentional dopant). A strong increase in Ho 3+ emission intensity and activation of Cr 3+ ions are accompanied by enhanced oxygen and other defect related luminescence. The structural analysis shows that during annealing new AlN crystallites form in the initially mostly amorphous AlN matrix.