Light induced electron spin resonance in porous silicon

Abstract

We report on the observation of a new metastable light induced defect center in porous silicon which has a g tensor with 〈110〉 symmetry and which is similar to the thermal donor, NL8, seen in thermally annealed Si. The optical response has an onset in the vicinity of the Si indirect band gap. The time dependence of the response has a sharp rise followed by a nearly saturated regime. Changing to a higher photon energy then results in another marked increase in the response. We suggest that this dependence of the absorption on excitation energy reflects the distribution of crystallite sizes. We observe that near ultraviolet light significantly bleaches the signal.