Localized excitons and trions in semiconductor nanosystems

The optical properties of semiconductors and nanoheterostructures based on them are determined near the fundamental absorption edge by electron–hole complexes such as excitons and charged three-particle complexes, aka trions. We present the results of theoretical studies of the structure and binding energies of localized excitons and trions in nanosystems within the variational approach. This approach is applicable to a wide range of semiconducting systems, from quantum wells, wires, and dots based on classical group III–V and II–VI semiconductors to van der Waals heterostructures made of monolayers of transition-metal dichalcogenides. We also discuss many-particle effects in structures containing resident charge carriers. Our treatment of theoretical approaches is accompanied by a discussion of extensive experimental results available in the literature.