Photovoltaic spectra of pure and doped (Cu, Cd, Sb) samples of GaSe were measured at temperatures between 1.5 and 300K. The spectra are composed of a large background modulated by a fine structure whose excitonic origin is established. The presence of this fine structure in the vicinity of the indirect transition reveals the existence of an indirect exciton in GaSe. The effect of the excitonic coupling on the photovoltaic spectra is strongly dependent on the purity of the sample: it produces dips in pure crystals and peaks in doped ones. The corresponding recombination mechanisms of electrons and holes are examined and a model is proposed, which is consistent with earlier luminescence data.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics