Ultrafast carrier dynamics in undoped microcrystalline silicon

We have studied ultrafast dynamics of photoexcited carriers in mu c-Si:H by pump and probe laser spectroscopy. We have found that the dynamics of phot oexcited carriers in mu c-Si:H depend on the crystallinity of the material: in the samples with low crystalline fraction, the dynamics have a fast dec ay and resemble those in a-Si:H, while in the samples with high crystallini ty the dynamics are slower and similar to those in c-Si. We have identified an intensity dependent bimolecular recombination in the samples with lower crystalline fraction (coefficient B = 2 x 10(-10) cm(3) s(-1) for depositi on with silane dilution ratio approximate to 5% at a fixed power of 6 W), a nd no bimolecular recombination in the samples with high crystallinity. (C) 2000 Elsevier Science S.A. All rights reserved.