Impact ionization of excitons in single-crystal silicon and its effect on the exciton concentration and luminescence near the fundamental absorption edge

The effect of impact ionization of excitons by free charge carriers on the exciton concentration in single-crystal silicon ( c -Si) at room temperature and at a high injection level is investigated. At sufficiently high concentrations of free electrons ( n ), the impact ionization dominates over thermal ionization. At such n , the effect results in much lower exciton concentrations ( n ex ) compared to those with disregard of it and linear or almost linear portions in the dependences n ex ( n ) and the dependences of the near-band-edge luminescence intensity in c -Si on the intensity of its excitation. The proposed technique for calculating n ex can be developed for other semiconductors at other temperatures.