Photomemory effect in Cu2O single crystals. Phenomenology and interpretation

Various new experimental aspects of the photomemory effect in Cu2O single crystals are investigated. They are interpreted on the basis of the model previously worked out for the electrical conductivity. The pre-illumination of a sample increases its bulk conductivity (by a factor up to 104) and shifts downwards the Fermi level (by an energy up to 0.3 eV). This excitation is explained in terms of electron trapping. Direct evidences reveal the existence of four trapping levels. The saturation of the excitation is attributed to the presence, in the acceptor distribution, of strong recombination levels. The study of the wavelength dependence of the photoexcitation allows to confirm the proposed energy diagram and to precise the position of the recombination levels. Finally, the effect of excitation on the Hall mobility is investigated.