With the use of the contact exciton model, the influence of a finite concentration of conduction electrons on the exciton energy is studied. Screening, gap renormalization, and the Burstein shift are taken into account. The absolute exciton energy increases with carrier concentration, while the binding energy decreases. However, no Mott transition occurs.

• Received 10 September 1984

DOI:https://doi.org/10.1103/PhysRevB.32.2631