Preparation Of Porous Silicon And Study Of Itsluminescence Properties

Silicon material is a very important and frequently-used semiconductor material in the microelectronic and modern information technology, but silicon is also an indirect band gap semiconductor materials, which made the luminescent efficiency very low. The appearance of porous silicon solved the problem that the luminescent efficiency of silicon is not ideal. The luminescent efficiency of silicon not only improved, but also can emit luminescence of visible light to the naked eye. Currently, researches on porous silicon have been into the application areas while there are still so many problems to be solved in theory and practice.The morphology of porous silicon is one of the main factors that affect the luminescence of porous silicon. In this paper, the influence of preparation conditions(including the distance h between cathode and anode, the etching time t, the etching solution concentration c, the etching current density J)on the morphology and photoluminescence of porous silicon will be researched. Firstly, we introduced the developed history of porous silicon, preparation methods, formation mechanism, luminescence mechanism and application areas; next, we introduced the experimental materials and apparatuses, experimental device and steps of single groove electrochemical etching method and made a brief introduction of the methods of characterization; we produced porous silicon samples in different etching conditions by control variable method and used scanning electron microscope(SEM), transmission electron microscope(TEM), optical microscope and photoluminescence(PL) spectrum to observe the morphology and luminescence property of porous silicon, which made us research the influence of preparation conditions on porous silicon.Experimental results indicated: when the distance between cathode and anode is changed, a lot of good quality porous structure appeared and several special morphologies which were never watched appeared, such as crater structure and silicon pillar cluster around it, silicon nanowire structure, skeleton structure and so on. And the reasons of these structures were analyzed briefly. SEM images showed that several crater structures were formed on the surface of the sample and there was silicon nanowire structure under the crater structure. The diameter of the nanowire can be dozens of nanometers. The appearance of silicon nanowire had great significance which provided a new electro-chemical method produced silicon nanowire for the future research. PL spectrum showed the luminescence property of crater structure and porous silicon around it. The peak wavelength of porous silicon is at 650 nm, while the peak wavelength of crater structure is at 600 nm. The reason of this phenomenon may be that there were several silicon pillar clusters containing a lot of silicon nanowires, which caused the peak wavelength to move to the blue shift and the photoluminescence intensity to become bigger. A lot of researches are needed in order to understand the formation process of morphologies.