Study Of High Quality Poly-Si Films By Aluminum-induced Crystallization For Thin-film Solar Cells

Recently, growth of high-quality poly-Si films remains as one of the most important subjectsdue to the advantages of low cost thin-film technology and the superior optoelectronic properties ofcrystalline Si. An attractive technique for the preparation of poly-Si films is aluminum-inducedcrystallization (AIC) because it offers a lower thermal budget than other crystallization methods,the possibility to use low-cost substrates and the generation of grains that are larger in size than thethickness of the poly-Si films.Glass/Al/a-Si composite layer was deposited using rf-magnetron sputtering and the poly-Sithin film was fabricated by AIC. The influences of precursor a-Si films and annealing technologyon the AIC process and the quality of fabricated poly-Si thin films were studied. The poly-Si thinfilms with excellent structural properties were fabricated at a low cost successfully. The mostimportant results are achieved as listed below.The influences of RTA and conventional furnace annealing on the nucleation and growth ofpoly-Si thin films during AIC process have been compared and investigated. It was found that,compared to furnace annealing samples, the RTA samples had a shorter nucleation time and ahigher nucleation density, also a reduced process time to form continuous poly-Si films. The fullycrystallized poly-Si films annealed by both RTA and conventional furnace exhibited goodmicrostructures with Raman peaks at518cm-1and FWHMs of6.48and6.43cm-1, respectively.The effect of hydrogen content on AIC of hydrogenated amorphous silicon (a-Si:H) films hasbeen studied. It was found that, with the increase of H content, the crystallization process of AIC ofa-Si:H films was fast at first and then became slower. It was possible to suppose that the hydrogenbonded as monohydride (SiH) band suppressed the crystallization, but the dihydride (SiH2) bond inthe a-Si:H films promoted the AIC process.The influence of aided electric field on the AIC of a-Si films has been studied. It was foundthat, whether or not an electric field was applied and no matter what direction of the electric fieldwas adopted, the crystal volume fraction increased with the increase of process time. After the electric field with intensity of100V/cm was applied to the samples when annealing, it was foundthat, the parallel electric field suppressed the crystallization and the vertical electric field promotedthe AIC process.