On-chip optical interconnects one step closer
The findings published in Nature Photonics relate the monolithic integration of arrays of indium phosphide lasers directly on 300mm silicon substrates in a CMOS pilot line. This is one step further in the integration of photonic integrated circuits (PICs) where optical signal conversion could support on-chip or in-package optical interconnects between logic and memory chips.
Using a production grade metal-organic vapor-phase epitaxial (MOVPE) growth reactor, indium phosphide semiconductor was selectively grown on silicon in a pre-patterned oxide template , realizing indium phosphide waveguide arrays across the entire 300mm substrate.
Subsequently, periodic grating structures were etched in the top layer of these waveguides, providing the optical feedback required for laser operation. Lasing operation was demonstrated for all tested devices consisting of an array of ten indium phosphide lasers.
Typical lasing threshold powers of around 20mW were observed at room temperature under optical pumping. The researchers reported a small variability of lasing performance along the array, hinting at the high material quality of the hetero-epitaxial grown indium phosphide. They also demonstrated their ability to accurately control the lasing wavelengths distribution across the array, by modifying the grating parameters. The 300mm CMOS pilot line used for this research guarantees a path to large volume manufacturing.
Now the researchers are investigating the growth of more complex layer stacks to enable electrical injection of the lasers and emission in the 1300nm wavelength range, along with integration with silicon based waveguide devices.
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