Excitons and exciton-phonon interaction in atomically thin nitrides

In this work, we explore excitonic properties and exciton-phonon interactions in atomically thin nitrides, highlighting their potential for optoelectronic and excitonic devices. First, we investigate atomically thin GaN quantum wells, just a few atomic layers thick, encapsulated within Al(Ga)N barriers. The strong confinement in these quantum heterostructures significantly increases the bandgap, enabling deep-UV emission and enhancing exciton binding energy, improving radiative efficiency. Second, we examine how strong exciton binding and exciton-phonon coupling in bulk h-BN enable efficient deep UV emission, despite its indirect bandgap. We also find that monolayer h-BN on graphite substrate exhibits significant renormalization of its electronic bandgap and exciton binding energy due to strong screening by the graphite substrate. Finally, we present a theoretical framework for phonon screening of excitons to accurately assess exciton binding energy in reduced-dimensional systems. We reveal that in atomically thin semiconductors, vibrational modes confined exclusively to the barrier or substrate region, known as half-space (HS) modes, can greatly influence screening of excitons.