Study On Properties Of Electroluminescence From Porous Silicon

Traditionally, crystalline silicon(c-Si) is the most important semiconductor material of integrate circuit and microelectronics. People hope for photoelectron integration on silicon basis. However, because silicon's band gap is 1.12eV, and it belongs to indirection gap materials, it is unsuitable for many optoelectronic purposes. In 1990, Canham detected that porous silicon could emit visible light at room temperature. The bright visible photoluminescence and electroluminescence from porous silicon have changed traditional concept that silicon can not be used in photoelectron domain. This shows promising foreground of photoelectron integration on silicon basis. Seeing from applied apparatus, people pay more attention to electroluminescence from porous silicon than to photoluminescence from porous silicon.In this dissertation, liquid electroluminescence device of porous silicon was prepared. The electroluminescence properties of this device were investigated. Heterojunction light-emitting diodes with ITO/p-Si/PS/AI structure were fabricated. The light emission lasted for a few hours under 7.5V forward bias conditions. The electroluminescence properties of this device were studied. Influences of preparation conditions on electroluminescence of porous silicon were analyzed systematically. Thermal annealing effects on electroluminescence from porous silicon were studied. Post-treatment technique of porous silicon, immersing porous silicon in the (NH₄)₂S/C₂H₅OH solution, was studied.The first chapter was about the summarization of the applied investigation on porous silicon. The achievement and foreground of applied investigation on porous silicon were narrated. Studies on photoluminescence, electroluminescence and passivation of porous silicon were summarized.The second chapter was about studies on properties of liquid electroluminescence device of porous silicon. In this chapter, two different carrier injection mechanisms were introduced. Porous silicon was prepared byelectrochemical anodized method, and then immersed into 1 mol-L"1 NaCl liquid. Two-step anodic oxidation caused strong light emitting from surface of porous silicon. Its light emission mechanisms were analyzed.The third chapter was about studies on properties of electroluminescence from heterojunction light-emitting diodes. Using electron beam coating, aluminum was deposited on p-type single crystal silicon. Then, porous silicon was prepared by electrochemical anodized method. Finally, ITO thin films were deposited on porous silicon by pulsed laser deposition method and the samples with ITO/p-Si/PS/Al structure were obtained. Light emission emanating from the top surface through the transparent emitter was observed under 7.5V forward bias conditions, and lasted for a few hours. Electroluminescence properties and carrier injection mechanisms were analyzed. Influences of preparation conditions on electroluminescence from porous silicon were studied.The fourth chapter was about effect of passivation on properties of electroluminescence from porous silicon, hi order to enhance intensity and stabilization of light-emission from porous silicon, two different post-treatment techniques of porous silicon were studied. One was thermal annealing method. The other post-treatment technique was immersing porous silicon in the (NRt^S/CiHsOH solution. These two methods could enhance intensity and stabilization of light-emission from porous silicon.In the fifth chapter, the experiments mentioned above were summarized.