402. S. Ren, T. I. Kamins, and D. A. B. Miller, “Thin Dielectric Spacer for the Monolithic Integration of Bulk Germanium Quantum Wells With Silicon-on-Insulator Waveguides,” IEEE Photonics Journal 3, No. 4, 739 – 747 (August 2011)
We propose an approach to monolithically integrate bulk germanium or germanium quantum wells with silicon-on-insulator waveguides through selective epitaxy and direct butt coupling. To prevent lateral epitaxial growth during the selective epitaxy, a dielectric insulating spacer layer is deposited on the sidewall facet of the SOI waveguide. With a SiO2 spacer of 20nm thick, the additional insertion loss penalty can be as low as 0.13 dB. We also propose and demonstrate a robust, reliable, and CMOS-compatible fabrication process to realize sub-30nm spacers.
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