High density photoluminescence induced by laser pulse excitation in InSe under pressure

Abstract

We report on high density photoluminescence (HDPL) measurements in undoped indium selenide under pressure at 300 K. Direct electron-hole plasma (DEHP) stimulated emission, induced by high density excitation, has been observed in InSe from room pressure up to 5.1 GPa. Spontaneous and stimulated emission bands observed in the spectra have been analyzed within the framework of the band gap renormalization theory (BGR) in a multi-valley scenario. The pressure coefficients of the spontaneous and stimulated emission bands have led us to attribute these bands to transitions from different minima in the conduction band, which show different renormalization energies determined by the effective masses and electron densities in each valley. Under high excitation, the direct to indirect crossover is shown to occur at a lower pressure than that observed in absorption measurements, as a result of the different renormalization energies of each transition.