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33LP-PS-6
Modeling of laser crystallization of thin amorphous layers of silicon under experimental conditions of cw laser irradiation
J. Beranek1, O. Aktas2, S. MacFarquhar2, Y. Franz2, S. Mailis3, N. M. Bulgakova1, A. C. Peacock2
1HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Dolni Brezany, Czech Republic
2Optoelectronic Research Centre, University of Southampton, Southampton, United Kingdom 3Skolkovo Institute of Science and Technology, Center for Photonics and Quantum Materials, Skolkovo, Russian Federation
Unique electrical and optical properties of crystalline silicon and silicon-based materials are of fundamental importance for applications in electronics, photovoltaics and communications. These materials have shaped the technical progress in many fields in recent decades. One of dynamically developing areas is silicon photonics [1], where nanoscale waveguides are finding use in components ranging from passive interconnects to active modulators and emitters. Such structures can be fabricated on various kinds of substrates and integrated with other electronic and optical components. However, the current methods used for producing high-quality crystalline silicon typically require high temperatures, which places important restrictions on device integration and miniaturization. On the other hand, amorphous silicon (a-Si) is relatively easy to deposit on various substrates at relatively low temperatures, but with inferior optical and electronic properties.
A solution to this problem is to fabricate high quality crystalline silicon waveguides and components by laser crystallizing deposited a-Si structures. Here we report our numerical investigations of laser processing of amorphous silicon waveguides for the experimental conditions with using a continuous wave (cw) argon ion laser. It was shown experimentally [1] that it is possible to obtain high optical quality poly-silicon waveguides by laser annealing of amorphous silicon films via heating to a temperature sufficient to melt the material but to avoid its noticeable evaporation that is consistent with our modelling and interpretation of the physical processes for the case of silicon optical fibers [2].
In this work, we report on the modelling of another waveguide geometry for exploring the temperature evolution of a-Si irradiated by cw laser at 488 nm wavelength. Physical modelling of laser-matter interaction provides an important insight for laser microfabrication as the processes of laser energy absorption, heat transfer and cooling during fabrication create specific conditions that affect the grain formation and growth and, therefore, influence the quality of final structure [3]. It allows to better understand the process of silicon crystallization in different regimes and can help to overcome drawbacks in production of high-quality silicon structures. To model thermodynamic changes in each particular case, it is necessary to develop a numerical code operating with high temporal and spatial resolutions, which is tailored to specific 2D and 3D geometries.
In our modeling, the irradiated samples represent the stripes of amorphous silicon with width of 1-2 p,m and thickness of 400 nm located on a glass substrate that are used in experiments. For this aims, we apply a finite-difference implicit scheme with splitting by the coordinates that provides high stability at reasonable simulation times and goodenergy conservation. The dynamics of laser heating in melting of a-Si in such geometry will be analysed with deriving the time of complete melting and the heat transferred to the glass substrate.
References
[1] Yohann Franz et al. Laser "Annealing of Low Temperature Deposited Silicon Waveguides", Conference on Lasers and Electro-Optics (CLEO), OSA Technical Digest (online) (Optical Society of America, 2017), paper SM3K.4.
[2] N. Healy et al., "Extreme electronic bandgap modification in laser-crystallized silicon optical fibres", Nat. Mater. 13, 1122-1127 (2014).
[3] N. H. Nickel, "Laser Crystallization of Silicon - Fundamentals to Devices", Chapter 1 (Academic Press, 2003).
