| Silicon-based photonics and silicon monolithic optoelectronic integrated is currently one of the most attractive topics and how to realize the silicon-based light source is an urgent and changeling problem. So far, many approaches have been developed to overcome the limitations of the bulk silicon material. In order to obtain efficient silicon based light-emitting materials and devices, it is necessary to systematically study the fabrication, microstructure and opto-electronic properties of Si-based light-emitting materials, among them, nanocrystalline silicon is a potential candidate and has been studied in a worldwide range.Based on our previous work, we further developed the laser induced constraint crystalliza-tion technique to crystallize amorphous Silicon (a-Si)/SiO2multilayers and a-Si/SiNx sand-wiched structures grown in plasma enhanced chemical vapor deposition (PECVD) system. Af-ter laser crystallization, nc-Si QDs/SiO2(or SiNx) films were achieved and the dot size can be as small as1.8nm. The electroluminescence was observed from the crystallized samples and the luminescence behaviors have been investigated systematically. We also used the laser crystallization technique to prepared doped nanocrystalline/microcrystalline silicon thin film on quartz substrates with high electrical conductivity and the influences of the doping concen-trations, film thickness and laser fluence were studied and discussed.The main contents and results of this thesis are as follows:1. We fabricated Si quantum dots (QDs)/SiO2multilayers by using KrF excimer laser (248nm) crystallization of amorphous Si/SiO2multilayered structures deposited on ITO coated glass substrates. Raman spectra and transmission electron microscopy demonstrated the formation of Si QDs and the size could be as small as1.8nm. After laser crystallization, Al electrode was evaporated to obtain light emitting devices and the room temperature electroluminescence was detected with applying the DC volt-age above8V on the top gate electrode. The luminescent intensity increased with increasing the applied voltage and the micro-watt light output was achieved. The EL behaviors for samples with different Si dot sizes were studied and it was found that the corresponding external quantum efficiency was significantly enhanced in sample with ultra-small sized Si QDs.2. Amorphous SiN/amorphous Si/amorphous SiN sandwiched structures were prepared by plasma-enhanced chemical vapor deposition. Raman spectra demonstrates the for-mation of Si quantum dots(QDs) with average size of2.8nm and4.7nm when the laser energy is above320mJ and the size can be controlled due to constrained crystal-lization in sandwiched structures. Room temperature electroluminescence (EL) can be detected with applying the DC voltage above10V and effect of laser fluence and size of Si QDs was evaluated. We attribute the EL spectrum peaks at680nm (2.8nm QDs) and720nm (4.7nm QDs) to the radiative recombination of injected electrons and holes within the Si QDs, which is accordance with the quantum confinement mechanism.3. The boron (B)-doped amorphous silicon thin films on quartz substrates were fabricated in PECVD system. After laser crystallization, B-doped nanocrystalline/microcrystalline silicon thin films with high conductivity were obtained by controlling the doping con-centration, thickness, and laser fluence. The sheet resistance of the crystallized thin film is about113Omega/square. Moreover, we obtained patterned microcrystalline silicon films by using one-dimensional or two-dimensional phase-shifting gratings and the surface morphologies were characterized by AFM technique. It was found that the clear patterned structures can be formed on the film surface when the laser energy was below230mJ. |
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