Localised transitions in luminescence of AlN ceramics

• UV and Blue emission in AlN ceramics is due to donor–acceptor pair recombination.
• UV emission band is produced by recombination of ON-vAl (acceptor) and ON (donor).
• In AlN ceramics donor–acceptor pairs are randomly distributed by separation distance.
• Model implies transitions from excited state of donor to ground state of acceptor.
• DAP separation determines recombination probability and luminescence features

The photoluminescence (PL) and thermoluminescence (TL) properties of AlN ceramics revealed under UV irradiation are determined mainly by oxygen-related centres, giving rise to the UV (around 3.18 eV) and the Blue (2.58 eV) bands. It was found that the UV irradiation-generated donor–acceptor pairs (DAPs), responsible for the UV emission band, are randomly distributed with regard to separation distance. Luminescence properties of AlN are interpreted basing on the model of localised recombination involving electron tunnel transitions from the excited state of D to the ground state of A, proposed by Jain et al. (2012). The observed features of PL, afterglow and TL of AlN ceramics are explained by dependence of tunnelling recombination probability on separation distance between D and A implied by the used model.