Phonon-assisted photoluminescence and exciton recombination in monolayer aluminum nitride

Abstract Efficient solid-state photon emitters with longer operating lifetimes in the ultraviolet (UV) wavelength range are crucial for optoelectronic devices. However, finding suitable material candidates has been a significant challenge. Here, we investigate wide bandgap hexagonal aluminum nitride (h-AlN) monolayers, a potential material candidate for efficient UV light source. From first-principle calculations, we investigate impact of electron–phonon interaction (EPI) on single-particle spectrum and temperature-dependent bandgap renormalization of h-AlN monolayer. Additionally, temperature-dependent optical absorption and emission studied from finite-temperature Bethe–Salpeter equation (BSE) show significant impact of EPI. We calculate temperature-dependent non-radiative linewidths using the exciton–phonon coupling function that gives a parameter free exciton lifetimes. We demonstrate that h-AlN monolayers exhibit strong photoluminescence (PL) emission within the UV range of 3.94−4.05 eV. Furthermore, from the finite-momentum exciton spectrum calculation using BSE, we show that the PL emissions in indirect bandgap h-AlN are facilitated by phonon modes with finite lattice momentum. These phonon modes promote efficient recombination of electrons and holes having finite momentum difference (q). Our findings provide a foundation for developing advanced optoelectronic devices and efficient UV light sources based on h-AlN monolayers.