Evidence of the exciton-plasma transition in the emission spectra of GaSe

Summary We present luminescence spectra of gallium selenide at 2 K in which a slow and continuous evolution from excitonic recombination to an electron-hole plasma emission is observed when the excitation intensity is increased. We find a small red-shift and a broadening of the direct exciton emission line which is followed by its disappearing. We explain these results with a model which takes into account the electron-hole correlation. Part of this work was carried out during a stage at the Institut de Physique Appliquée of the Ecole Polytechnique Fédérale de Lausanne (Switzerland).