Near‐edge spontaneous photoluminescence in GaSe1–xSx

Photoluminescence spectra of GaSe1–xSx (0 ≦ x ≦ 0.2) are investigated at 4.2 K by the time resolving method. The shift in the photon energies of the luminescence lines with respect to the chemical composition x may be understood without any quantitative contradiction if one employs the empirical model that the direct conduction band edge lies 5 meV below the indirect one, whereas the ground state of the direct exciton lies 13 meV above that of the indirect one in ϵ, γ‐GaSe at 4.2 K. The direct–indirect gap reversal occurs near x = 1 × 10−2.