Luminescence of High Density Excitons in CdS, CdSe and ZnSe in the 4.2–90 K Temperature Range

Abstract

Luminescence spectra of high density excitons in CdS, CdSe and ZnSe are studied in the 4.2–90 K temperature range. As temperature increases, the luminescence line of excitonic molecules in CdS and CdSe disappears due to the thermal dissociation. The P line originating from the inelastic collision of two single excitons grows up to 30–40 K in all the materials due to the increase of the number of free single excitons. Above these temperatures the P line peak shifts to the low energy side accompanied by the broadening of the line shape. This is ascribed to the replacement of the dominant scattered state in the collision process from the bound excited state to the continuum state of the exciton. A new luminescence line located a little below the exciton line becomes to grow above 15–30 K. This line is assigned as due to the inelastic collisionof an exciton and an electron.