Impact ionization of excitons and electron-hole droplets in silicon

The low-temperature photoluminescence of bound excitons and electron-hole droplets in $n$-type Si is studied in a weak electric field for the first time, using simultaneous pulsed excitation for both the laser excitation and the applied electric field. The luminescence is quenched because of impact ionization by field-accelerated electrons and holes. The quenching starts around 50 V/cm, depending on sample purity and excitation intensity.