Recombination kinetics of excitonic molecules and free excitons in intrinsic silicon

Abstract

The luminescence decay characteristics of the excitonic molecule (EM) - free exciton (FE) system in pure silicon are described and explained in detail by a pair of coupled differential equations governing the time decay of the EM and FE densities. Comparison of the theoretical and experimental decays shows that the EM decay time is 59 ns and the capture coefficient at 1.8° K for the formation of an EM from two FEs is about 2 × 10-9 cm3/sec. These data imply the EMs decay primarily by a nonradiative Auger mechanism, which accounts for the low radiative efficiency.