Electron spin resonance and photoluminescence measurements were performed on porous samples. The results revealed the presence of O shallow donors with binding energies of the order of 0.1eV. These exhibited a distinct correlation with the intensity of the red photoluminescence which was observed in porous samples. It was suggested that the shallow donors became paramagnetic via the photo-induced capture of carriers that were created by light absorption in the Si crystallites. A model was proposed that linked the presence of the shallow donors to the presence of non-bridging O hole centers. These were thought to be responsible for the intense red photoluminescence that had been reported for porous Si.

S.M.Prokes, W.E.Carlos, O.J.Glembocki: Physical Review B, 1994, 50[23], 17093-6