Luminescencent Properties Of Silicon-based Compound Materials

In the 21st century, people's lives are being rapidly improved with the development of science and technology; however, the energy shortage, environmental pollution and global warming have become the most critical issue facing the survival of mankind. The usage of new clean energy, such as the development of the silicon-based solar cells, should be human's prime choice of response to the crisis. High quality silicon materials can be applied to solar cells, meanwhile oxides and nitrides such as SiO₂ and SiN_x films are important parts of the solar cell due to its excellent passivation and reduced adverse effects. At the same time, SiO₂ and SiN_x have also been widely adopted in the field of information technology such as integrated circuits capacitors, resistors, inductors, as well as memories. While in the field of optoelectronics and microelectronics, higher operating efficiency is the natural goal in the development of solar cells, it is frustrating with cost and conversion rate being the bottleneck. So far, the new semiconductor materials is still in the early years of research due to indistinct of the basic physical properties and mechanisms, therefore more study is needed.This thesis mainly includes the following two parts:1. The band structures of Si/SiO₂, Si/SiN_x/SiO₂ and Si/SiN_x/SiO₂/SiN_x multilayer quantum wells have been theoretically calculated using Kronig-Penney model and further analysis of the various sub-layer film thickness on the band structure and effective mass has also been done. It is found that the band gap of nano-Si films is obviously increased with appropriate reduction of the sub-layer in the thickness. As is known, the bandgap of Si quantum well layer conforms to the equation of E_PL(eV)= 1.6 + 0.7 /d²for Si/SiO₂ superlattice; our results show good agreement with such relationship. Based on our calculation, the light emission can be effectively controlled by adjusting the thickness of sub-layer, especially, the thickness of Si and SiN_x in the case of Si/SiN_x/SiO₂ and Si/SiN_x/SiO₂/SiN_x superlattice system.2. The SiO₂ film with a thickness of 630nm has been grown on Si(100) by LPCVD and annealed from 450～1000oC under N₂ flow for 20 minutes. The properties of SiO₂ films have been characterized by photoluminescence spectroscopy (PL), infrared spectroscopy (IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Two light emitting peaks were located at 380 nm and 720 nm in the PL spectrum. With the increase of annealed temperature in the range of 450⁷50 oC, the intensity of PL spectrum first increases and shows a blue shift of the peak around 380nm. However, the opposite variation occurs to the SiO₂ films as the annealed temperature increases from 750¹000 oC. The light emission of the SiO₂ film is believed to come from the interface defects between Si/SiO₂ on the basis of various measurements including infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy.