Deep ultraviolet photodetector based on high-quality cubic-AlN single-crystal films with nitrogen vacancies

Cubic aluminum nitride (c-AlN) has been regarded as a promising candidate for deep ultraviolet photodetectors. However, its epitaxial growth has been hindered by the intrinsic metastability of this phase. Herein, we demonstrate the direct epitaxial growth of high-quality single-crystalline c-AlN films with (100) orientation on MgO substrates via pulsed laser deposition. C-AlN films with different nitrogen vacancy (NV) concentrations were produced by adjusting the post-growth annealing process. Technology computer aided design simulations show that a high-NV concentration plays a key role in boosting photoresponsivity. Specifically, the unannealed c-AlN films achieved a maximum responsivity (R) of 107 μA·W−1 and a detectivity (D*) of 2.14 × 109 Jones under 254 nm illumination, significantly surpassing their annealed counterparts. This work offers an effective approach for fabricating photoresponse single-crystalline c-AlN films.