Imec and Ghent University demonstrated arrays of indium phosphide lasers monolithically integrated on 300mm silicon substrates in a CMOS pilot line. The researchers described the achievement in an article in Nature Photonics.
The researchers contend that the method they used to fabricate the InP lasers on a silicon substrate could lead to high-volume manufacturing of cost-effective photonic integrated circuits (PICs) with monolithically integrated laser sources.
The researchers assert that such laser-powered PICs could revolutionize data transfer between future logic and memory chips.
Wide-spread adoption of compound semiconductor laser technology on silicon has been hampered in part by the lack of monolithically integrated laser sources. The large lattice mismatch between silicon and InP is known to be very challenging.
Imec and Ghent University overcame the lattice mismatch and largely suppressed the detrimental crystal defects that typically form between silicon and indium phosphide. They used a production-grade metal-organic vapor-phase epitaxial (MOVPE) growth reactor to selectively grow the indium phosphide on a pre-patterned oxide template.
The growth formed indium phosphide waveguide arrays across the entire 300mm substrate. Subsequently, they etched periodic grating structures in the top layer of these waveguides, providing the optical feedback required for operating the lasers. They demonstrated lasing operation for all tested devices in an array of ten indium phosphide lasers. Under optical pumping, they observed typical lasing threshold powers of about 20mW at room temperature. The lasing performance showed small variability along the array, illustrating the high quality of the heteroepitaxial grown indium phosphide. In addition, they demonstrated accurate control on the distribution of the array’s lasing wavelengths by modifying the grating parameters.
Ongoing research efforts intend to focus on growing more complex layer stacks to enable electrical injection of the lasers, emission in the 1300nm wavelength range, and integration with silicon-based waveguide devices.