Optical characterization of reverse biased porous silicon light emitting diode

Optical characterization of porous silicon (PS) light emitting diodes (LED) formed in the transition regime and with an alumina passivating coating has been performed to understand the light emission mechanism. Fourier transform infrared reflection investigations, photoluminescence (PL), electroluminescence (EL) and Raman scattering measurements have been used. The investigated LED shows a visible emission band both for PL and EL, and a broad structured emission in the infrared for EL. The origin of visible EL and PL may be ascribed to carrier recombination in Si nanocrystals and in the defected oxide which coats them. The origin of infrared EL can be explained by band-to-band recombination in Si grains with large sizes (L≥6 nm) and by dislocation related emissions (D1 line). Possible improvements of the presented light emitting diode structure have been discussed.