Simultaneous Direct and Indirect Recombinations in the Electron-Hole Plasma of GaSe

We measured the spontaneous recombination luminescence spectra of the electron-hole plasma in GaSe at liquid He temperature. In order to reduce the effects of inhomogeneous carrier density, pinholes and thin samples were used. Since direct and indirect conduction band minima are almost degenerate in GaSe, it is assumed that the plasma contains direct as well as indirect electron-hole pairs. Two lines are observed which are assigned to simultaneously occurring direct and indirect recombinations. The model accounts for spectral positions and line shapes of the experimentally observed emissions. Best fits of the spectra yield the densities of the different carrier species and their temperature