Edge luminescence and light absorption in GaSxSe1−x solid solutions at low temperatures

As a result of experimental investigations of the luminescence and absorption spectra of GaSxSe1−x single crystals at 4.2°K and theoretical calculations, the band shift scheme for the GaSxSe1−x system when replacing Se by S is constructed. The analysis of the results obtained together with the data available in literature allow to draw conclusions about the layered character of the GaSe conduction band in the range of the indirect gap (M3 + point). The possible influence of such a peculiarity of the conduction band at the M3 + point on the probability of intervalley transitions in GaSe is discussed. Experimental results obtained indicate, that the indirect gap value 2.080 eV of GaSe, available in literature, has been underestimated. The photoluminescence spectra are interpreted as a result of radiative impurity transitions and their phonon replicas. The nature of the edge luminescence centres in GaSxSe1−x single crystals is discussed.