Photoluminescence in GaSe

Photoluminescence of GaSe is measured between 4.2 and about 40 K. The spectra of many samples are classified into three types. The first type has only one broad peak at about 2.04 eV, and the second type has two sharp lines at 2.096 and 2.088 eV followed by some lines at the lower energy side. The last one contains a direct free exciton line at 2.108 eV followed by fine structure. The variety of the spectra is interpreted by the change of the relaxation rates of the excited electrons into the direct minima and into the indirect minima of the conduction band which may be perturbed by the fine cracks on the surface of the sample.