A new bound-exciton emission band in ZnSe crystals and multiplasmon optical transitions

We have investigated cathodoluminescence both in unannealed ZnSe crystals and in crystals annealed in a Bi melt at a temperature of 1200K for 120 h with subsequent quenching. In the wavelength range 450–480 nm we have detected a new line series I i s -nLO-mPl consisting of the bound-exciton emission line I i s with wavelength λ=455.9 nm and its plasmon and LO-phonon echoes I i s -LO (λ1=461.3 nm), I i s -2LO (λ2=466.8 nm), I i s -3LO (λ3=472.4 nm), and I i s -4LO (λ4=478.3 nm). We have determined the mean number of emitted LO phonons NLO=2.2±0.1 per photon. It is shown that the observed finer structure of the band may be due to multiphonon optical transitions. At low plasma densities (ω p ≪ω LO ) the Coulomb interaction causes broadening of the I i s -nLO series. In samples with denser plasma, in which the condition ω p ⩽ω LO is met, multiplasmon satellites of the series I i s -nLO-mPl are observed. Theoretical calculations of the shape of the emission band agree with experiment.