Impact ionization of free excitons and electron-hole droplets in silicon in weak electric and magnetic fields.

Abstract

Impact ionization of free excitons (FE's) and electron-hole droplets (EHD's) in silicon by hot free carriers have been studied in weak electric fields at low temperature (2 K) via photoluminescence (PL) quenching experiments. The results show that the PL quenching for the FE and EHD are strongly related, so that the FE quenching behavior depends very much on the presence of the EHD phase. When no EHD's are present the PL quenching for the FE starts at quite low fields (about 20 V/cm), while in the presence of EHD's the onset of PL quenching is very much delayed, and may not be completed below the breakdown field. A strong influence of a transverse magnetic field on the electric-field-induced impact ionization of both the FE and the EHD is also observed.