Effect of Structural Changes Induced by Annealing Atmospheres on Luminescence of Eu²⁺‐ and Eu³⁺‐Doped AlN Thin Films

Europium (Eu)‐doped aluminum nitride (AlN) thin films can exhibit white light emission, which consists of the green and red emissions from the different valence states of Eu ions (Eu 2+ and Eu 3+ ) and the blue luminescence from vacancies formed in AlN. Thus, controlling the valence state of Eu ions makes them potential applications in white light‐emitting diodes. This study investigates the effects of annealing in/at the different atmospheres, O 2 , or N 2 /temperatures on the valence state and luminescence properties of Eu‐doped AlN. X‐Ray absorption fine structure and photoluminescence (PL) results suggest that high‐temperature annealing in an N 2 atmosphere increases the presence of Eu 2+ , whereas in an O 2 atmosphere, the concentration of Eu 3+ increases with rising temperature. PL results indicate that this change is attributable to the reduction of N ions and/or alterations in the bonding atoms surrounding Eu ions. Consequently, the adjustment of annealing atmosphere and temperature is crucial for controlling the ratio of Eu 2+ to Eu 3+ .