Study Of The Optical And Electrical Properties Of Porous Silicon

Porous silicon (PS) has attracted a lot of attention recently because it could exhibits photoluminescence (PL) at room temperature, and potentiality for the implementation of high-performance solid state electroluminescent (EL) devices, compatible with silicon integrated circuit technology. There are at present, however, at least two factors hampering its successful development and use of solid state EL devices. Firstly, most reported EL devices were plagued by extremely low external quantum efficiencies. Secondly, probably more serous than the first one, is their poor stability. A lot of works try to improve efficiency and stability of PL and EL for PS. In this thesis, we investigated the optoelectronic properties of PS.By using the modified Maxwell-Garnet model, the influence of porosity on reflection spectra of porous silicon was investigated .It was found that (1) the reflection index was enhanced first and then reduced with increasing incidence wavelength and the reflection spectrum emerged a tendency of collapse with increasing porosity, and (2) the porous silicon dielectric spectrum was blue-shifted and the real part and imaginary part reduced with increasing porosity. These phenomena were interpreted reasonably.Based on the influence of mirror image potential on I-V characteristic, the carrier transport process and the voltage drop distribution in metal/porous silicon/silicon structure are analyzed and discussed. The results indicate that: the current is mainly influenced by the charge of surface state and the interfacial layer in the metal/porous silicon/silicon structure, and the voltages in every layer redistribute with the thickness of porous silicon layer, and the current decreases with the thickness increase regardless of forward or reverse bias voltage. The influence of mirror image potential on current can be neglected when the structure is applied forward bias voltage, but it becomes more and more importance with the reverse bias voltage increasing.A novel passivation technology of porous silicon (PS) surface, i.e., depositing tungsten film on the PS surface by magnetron sputtering deposition method, was developed. The morphologies, structure and photoluminescence (PL) of porous silicon and tungsten film were characterized using atomic force microscopy and PL spectrometer. The results indicated that the homogeneous and dense tungsten film could be obtained by magnetron sputtering deposition method on PS, which stabilized greatly the luminescent wavelength and intensity, and moreover enhanced the mechanical strength of PS.