Single-photon emitters in AlN grown on a sapphire substrate by magnetron sputter epitaxy

Epitaxial AlN films were grown on c-plane sapphire substrates using reactive magnetron sputtering. X-ray diffraction analysis confirmed the epitaxial nature of the layers. Although the rocking curve of the (002) reflection, with a full width at half maximum of 3550 arcsec, indicates a short coherence length, in-plane measurements demonstrate a clear epitaxial relationship. Raman spectroscopy revealed an in-plane strain, evidenced by a redshift of almost 8 cm-1 of the E2(high) phonon mode. Sub-bandgap photoluminescence mapping at room temperature revealed broad emission features in the visible range of around 2 eV. Second-order correlation measurements [g(2)(τ)] confirmed the presence of single photon emitters, with g(2)(0) values below 0.5, demonstrating anti-bunching and non-classical light emission. Despite a relatively low signal-to-noise ratio and moderate count rates, the observed single-photon behavior validates the potential of reactive sputtered AlN as a viable platform for quantum emitters. This work motivates reactive sputtering as an additional growth method to metal-organic chemical vapor deposition grown AlN layers as a host for quantum emitters.