Emission mechanism in highly excited state of red HgI2

Abstract

Emission spectra of a layer semiconductor, red HgI2, under the N2-laser excitation are investigated from 4.2 K to 77 K. At 4.2 K, two emissions are observed which are attributed to the radiative annihilation of an excitonic molecule, leaving a transverse and a longitudinal exciton. As temperature increases, the two emission bands disappear due to the thermal dissociation of the excitonic molecule. A new emission band in the range from 20 K to 50 K is associated with the inelastic-collision process of two single excitons. Above 35 K, there appear two emission bands associated with the exciton-electron and exciton-hole interactions.