Binding energy of excitons formed from spatially separated electrons and holes in insulating quantum dots

It is found that the binding energy of the ground state of an exciton formed from an electron and a hole spatially separated from each other (the hole is moving within a quantum dot, and the electron is localized above the spherical (quantum dot)–(insulating matrix) interface) in a nanosystem containing insulating Al$_2$O$_3$ quantum dots is substantially increased (by nearly two orders of magnitude) compared to the exciton binding energy in an Al$_2$O$_3$ single crystal. It is established that, in the band gap of an Al$_2$O$_3$ nanoparticle, a band of exciton states (formed from spatially separated electrons and holes) appears. It is shown that there exists the possibility of experimentally detecting the ground and excited exciton states in the band gap of Al$_2$O$_3$ nanoparticles at room temperature from the absorption spectrum of the nanosystem.