Ultrafast carrier dynamics in thin film nanocrystalline silicon

Susan L. Dexheimer; Keith E. Myers; Qi Wang

doi:10.1117/12.470437

11 June 2002 Ultrafast carrier dynamics in thin film nanocrystalline silicon

Susan L. Dexheimer, Keith E. Myers, Qi Wang

Proceedings Volume 4643, Ultrafast Phenomena in Semiconductors VI; (2002) https://doi.org/10.1117/12.470437
Event: Symposium on Integrated Optoelectronic Devices, 2002, San Jose, California, United States

Abstract

Thin film nanocrystalline silicon (nc-Si), a promising material for photovoltaic and optoelectronic applications, is comprised of nanometer-scale crystals of silicon embedded in a matrix of hydrogenated amorphous silicon. The degree of crystallinity of the material can be controlled by varying the deposition conditions, yielding materials that span the transition from the amorphous to the nanocrystalline state, and yielding variable grain size and crystalline fraction. Pump-probe measurements using optical pulses 35 fs in duration in the near-infrared were carried out on a series of nc-Si films of varying composition. Photoexcitation results in an induced absorbance signal with a nonexponential time dependence that is strongly dependent on excitation density. The response can be understood in terms of a multicomponent model that includes distinct contributions from each phase of the heterogeneous material. We observe a 240-fs exponential relaxation process associated with intraband relaxation in the silicon crystallites, a response characteristic of bimolecular recombination in the amorphous silicon matrix, and a long-lived component assigned to grain boundary states.

Citation Download Citation

Susan L. Dexheimer, Keith E. Myers, and Qi Wang "Ultrafast carrier dynamics in thin film nanocrystalline silicon", Proc. SPIE 4643, Ultrafast Phenomena in Semiconductors VI, (11 June 2002); https://doi.org/10.1117/12.470437

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