Investigation Of Porous Silicon-based Organic Materials Luminescence And Electrical Properties

Although silicon is the basic building block for most microelectronic circuits, the material has not been used to provide optical transfer of information. The development of silicon-based photo-electronics has been severely limited, due to the small and indirect band gap of silicon in room temperature. The observation of visible luminescence from porous silicon by Canham in 1990 has begun to revitalize silicon's role as optical electronics materials.In this paper, recent progress of electroluminescence from porous silicon was reviewed. And the properties of the composite structures formed by porous silicon and organic materials were investigated in detail.It was found that HF concentration, anodic current, and anodization time had effect on structures and light emission of porous silicon. The difference of the structure, which influenced the light emission of porous, was the result of the competition between diffusion current and thermion current.The composite of porous silicon and poly (9-vinylcarbazole) (PVK) was fabricated by spin coating. The experiment results showed that the photoluminescence (PL) intensity and rectifying characterization of the composite were improved by the annealing at lower than 120 C. The improvement was attributed to the evaporation of water and solvent by annealing. Furthermore, a weak electroluminescece peak at 555nm was found from the porous silicon/PVK composite. For the composites of porous silicon and MEH-PPV fabricated by spin coating, an overlap at certain extent was observed in the ultra-visible absorbance spectra and PL spectra. It was due to the energy transfer from porous silicon to MEH-PPV and the energy transfer caused the red shift in PL spectra.The spin coating and vacuum evaporation methods were used to assemble porous silicon with Alq, irrespectively. It was found the two systems had different luminescence mechanism. It was the carrier transfer from the porous silicon to the interface that caused the emission from PS/Alq fabricated by coating. However, the emission from PS/Alq fabricated by evaporation originated from Alq.Photo- and electro-luminescence properties of composites of porous silicon and PVK and Alq were investigated at last. Because the carrier transfer mismatch was large between porous silicon and Alq, it was found the multi-layers did not improve the electroluminescence. While after coating with PVK and Alq in porous silicon, light emission of composite was controlled by Alq.