Photoluminescence spectra of the layered semiconductor gallium selenide under intense picosecond laser-pulse excitations

The photoluminescence spectra of gallium selenide consist of two bands at both 77 and 300 K. The lower-energy part of the spectra is associated with stimulated emission. The higher-energy part of the spectra is assigned to the exciton-electron (-hole) scattering process at lower excitation intensity and to the electron-hole plasma at higher excitation intensity. From the analysis of the high-energy tails of the higher-energy part of the emission spectra, the transition from the exciton-carrier scattering emission to the electron-hole plasma emission at 300 K was obtained for an excitation intensity of about (1.70±0.25)×${10}^8$ W ${\mathrm{cm}}^{-2\mathrm{}}$.