Emission of free and bound excitons in layered gase crystals

The emission spectra of GaSe single crystals of ϵ‐modification doped with Co of 0.001 to 0.5 wt% concentration are investigated at different temperatures (T = 4.2 to 35 K) using polarized light. It is shown that the wide emission band with energy 2.031 eV is due to structural defects while the other wide bands of 2.039 and 2.008 eV are due to indirect exciton transitions with radiation of TO‐phonons. The narrow emission lines correspond to the decay of direct excitons bound on different defects and to their phonon sattelites involving phonons of (14.5 ± 0.5) meV. The temperature dependence of a doublet structure of the free exciton emission line, which is thought to be due to the peculiarities of the GaSe crystal band structure, namely the splitting of the valence band by inter‐layer interaction is investigated.