Secondary emission due to recombination of excitons near indirect band bottom. I. General feature

Abstract

The secondary emission, due to recombination of excitons in the vicinity of the indirect band bottom is investigated, where excitons relax their kinetic energy through multiple scatterings with acoustic phonons and a nonradiative decay process. In this case, the secondary emission can be separated into the two parts: the Raman scattering (RS) and the hot luminescence (HL). The spectral lineshape of the HL directly reflects the exciton distribution near the band bottom. The distribution has been calculated by the Fokker-Planck equation with the source term of exciton supply through the indirect absorption process. It is shown that the excitation spectrum of the RS line and the spectral structure of the HL strongly depend on the two quantities: the kinetic energy of an exciton with the sound velocity and the nonradiative decay rate. General features of RS, HL and their relationship are studied for a system with material constants appropriate to BiI3, since the experiments show that this is an ideal system for the authors' purpose.