Radiative Recombination Mechanisms in GaSe Films Prepared by Mechanical Exfoliation

Low-temperature (5 K) luminescence of GaSe films obtained by mechanical exfoliation of a bulk GaSe crystal. It is shown that, in contrast to initial GaSe, strong luminescence bands dominate in the luminescence spectra of such films; the spectral position of these bands are shifted by 60-80 meV with respect to the GaSe fundamental absorption edge. An increase in the excitation power density leads to a superlinear growth of the intensity of the detected bands, which is accompanied by the appearance of anti-Stokes luminescence with a photon energy of similar to 4 eV. The detected luminescence bands are identified with emission of electron-hole plasma localized near planar defects caused by perturbing relative positions of GaSe monolayers during mechanical exfoliation.