Mott transition of the excitons in GaSe.

Abstract

An optical study of the excitonic Mott transition in GaSe at liquid-He temperature is presented. In recording the optical spectra, care was taken to reduce the effects of the spatial inhomogeneity of the photoexcited carriers as much as possible. The transition we observed is smooth and continuous. We discuss the contribution of bound and dissociated electron-hole pairs to the screening of the carrier-carrier interaction. The observed red shift of the excitonic level with increasing carrier density agrees well with the prediction of our model, which is based on a simplified binary-collision approximation.