The role of the annealing temperature on the optical and structural properties of Eu doped GaN/AlN QD

Self assembled molecular beam epitaxy grown GaN quantum dots stacked with AlN spacers were implanted with Eu ions. The as-implanted samples were further submitted to thermal annealing treatments in nitrogen, between 1000 °C and 1200 °C. Eu3+ luminescence was observed in all samples with the most intense emission assigned to the 5D0 → 7F2 transition in the red spectral region. The preferential excitation paths of Eu3+ luminescence is explored using photoluminescence excitation measurements which allow us to identify the feeding mechanisms for the Eu3+ ions inside the GaN quantum dots and AlN host. Optically active Eu centres in both GaN QD and AlN layers could be identified. For low implantation fluence the Eu centres inside GaN QD are dominant while for high fluences the emission arises from Eu in the AlN layers. The annealing temperature, on the other hand, does not cause any change in the local environment of the Eu-ions.

Research highlights
► The purpose of the present article is to analyse the effects of the increasing post-implant annealing temperature on the optical and structural properties of Eu-doped GaN QD/AlN SL.
► We have shown that in Eu-implanted GaN QD/AlN SL samples the post-growth thermal annealing between 1000 and 1200 °C activates the Eu3+ luminescence in the SL structures.
► For low implantation fluence the Eu centres inside GaN QDs are dominant while for high fluences the emission arises from Eu in the AlN layers.
► The annealing temperature, on the other hand, does not cause any change in the local environment of the Eu-ions.