Formation of excitons in semiconductor nanostructures in the presence of electron-hole plasma

We propose a mechanism of increase in the binding energy of an exciton in wide band-gap semiconductors in the presence of optically pumped electron-hole plasma. These excitons with relatively high binding energy (>150 meV) can exist at room temperature when the dielectric constant of semiconductor in the infrared region of spectrum approaches zero. Calculations for CdS show that the density of electron-hole plasma should be higher than 10¹⁹ cm^?3 for formation of such excitons. We show that there exist a considerable number of close-lying energy levels of excitons with high binding energy in the forbidden band of the semiconductor. We guess that these excitons participate in the process of laser generation in optically pumped semiconductor nanocrystals.