MIDGAP LOCALIZED STATES AND LIGHT-EMISSION OF POROUS SILICON

Light emissions of porous silicon were studied by photoluminescence (P L) and photoluminescence excitation spectroscopies (PLE). The results suggest the existence of midgap localized states and provide strong ev idence of lattice relaxation effect. Visible light emission may be due to the electron transition between the modified conduction band and t he surface related localized states with the participation of phonon e missions. The Stokes shift between peaks of photoemission and photoexc itation spectra is about 1.2 eV and varies with different preparation and later treatment conditions of the samples.