Excitons and electron-hole plasma in InSe

The spontaneous emission from either thin or thick samples of layered indirect-gap InSe semiconductor under dye laser excitation has been investigated either above or below the critical Mott density. The observed spectra consist of five bands in the near infrared region; four of them are localized in the energy range between the direct and the indirect gap and one only lies below the indirect energy gap. These bands can be associated with cooperative indirect and direct excitonic transitions and with electronhole plasma recombinations.