Wannier–Mott excitons in GaSe single crystals

The absorption, reflection and photoluminescence spectra of GaSe crystals with different thicknesses (100 nm–1 mm) were investigated in a wide temperature interval (300 K–10 K). Features due to excitonic states in the spectra were recognized. The contours of the excitonic reflection spectra measured at 10 K were calculated by dispersion equations. On the basis of these calculations, the parameters of the observed excitons were determined. Photoluminescence spectra from the cleaved surface and from the uncleaved facet of a sample were measured at low temperatures.