Abstract
We report the fabrication of low-loss, low temperature deposited polysilicon waveguides via laser crystallization. The process involves pre-patterning amorphous silicon films to confine the thermal energy during the crystallization phase, which helps to control the grain growth and reduce the heat transfer to the surrounding media, making it compatible with CMOS integration. Micro-Raman spectroscopy, Secco etching and X-ray diffraction measurements reveal the high crystalline quality of the processed waveguides with the formation of millimeter long crystal grains. Optical losses as low as 5.3 dB/cm have been measured, indicating their suitability for the development of high-density integrated circuits.
Highlights
Over the past two decades, silicon photonics has emerged as a promising solution for the realization of high performance, high density photonic integrated circuits [1,2]
This work has led to the production of amorphous silicon (a-Si):H and silicon nitride (SiN) waveguides exhibiting similar or even lower optical losses than crystalline silicon (c-Si), which has allowed for the demonstration of several all-optical processing functions in integrated systems [10, 11]
We demonstrate the fabrication of low-loss polycrystalline silicon (poly-Si) waveguides via localized laser crystallization of micron-size stripes of low temperature deposited amorphous silicon (a-Si)
Summary
Over the past two decades, silicon photonics has emerged as a promising solution for the realization of high performance, high density photonic integrated circuits [1,2]. The fabrication of multi-layer c-Si structures typically requires the use of expensive and technically challenging wafer bonding processes [6] To overcome these limitations, significant efforts have been devoted to developing alternative, more flexible deposited materials such as hydrogenated amorphous silicon (a-Si:H) [7], silicon nitride (SiN) [8] or polycrystalline silicon (poly-Si) [9]. When deposited at low temperatures poly-Si materials typically form small crystals with numerous grain boundaries that act as scattering and absorption points [16] This results in relatively high optical losses, which have remained a limiting factor for the application of this material in photonic systems [9, 12, 13]. Optical transmission measurements have revealed a linear loss value as low as 5.3 dB/cm, paving the way for the development of high performance optoelectronic devices
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