Ionization equilibrium in an excited semiconductor: Mott transition versus Bose-Einstein condensation

The ionization equilibrium of an electron-hole plasma in a highly excited semiconductor is investigated. Special attention is directed to the influence of many-particle effects such as screening and lowering of the ionization energy causing, in particular, the Mott effect (density ionization). This effect limits the region of existence of excitons and, therefore, of a possible Bose-Einstein condensate at low temperatures. Results for the chemical potential and the degree of ionization are presented for zinc selenide (ZnSe). A possible window for the occurrence of a Bose-Einstein condensate of excitons is shown, taking into account the Mott effect.