Carrier localization in codoped ZnO:N:Al films

Temperature-dependent photoluminescence (PL) from p-type ZnO film codoped with Al and N has been investigated. In the whole temperature range of 10–300 K, the PL was dominated by a broad emission centered at 3.05 eV. The dependencies of its peak energy on temperature and compensation indicate that this emission is due to recombination of localized carriers. We suggest that the localization is due to potential fluctuations caused by strong compensation and local compositional fluctuations of the impurities. We obtain an activation energy of ∼69 meV from thermal quenching of the luminescence intensity and ascribe it to thermal ionization of shallow donors.