First full wafer-scale fabrication of electrically-pumped GaAs-based nano-ridge lasers on 300 mm silicon wafers

The results demonstrate the potential for direct epitaxial growth of high-quality III-V materials on silicon, enabling room-temperature CW generation with threshold currents as low as 5 mA and output powers greater than 1 mW.

This breakthrough paves the way for the development of cost-effective, high-performance optical devices for applications in data communications, machine learning and artificial intelligence.

The lack of large-scale light sources integrated into CMOS has become a major obstacle to the widespread adoption of silicon photonics.

Hybrid or heterogeneous integration solutions such as flip chip, microtransfer printing, or die-to-wafer bonding involve complex interconnection processes or the need for expensive III-V substrates that are often discarded after processing. This not only increases costs, but also raises concerns about sustainability and resource efficiency.

For this reason, direct epitaxial growth of high-quality III-V optically enhanced materials selectively on large-size silicon photonic wafers remains a highly sought-after goal.

The large mismatch in lattice parameters and thermal expansion coefficients between III-V and Si materials inevitably initiates the formation of crystal mismatch defects, which are known to degrade laser performance and reliability.

Selective area growth (SAG) coupled with aspect ratio trapping (ART) significantly reduces defects in III-V materials integrated into silicon by confining misfit dislocations to narrow grooves etched into the dielectric mask.

“In recent years, imec has pioneered the development of nanoridges, a technology based on SAG and ART to grow III-V nanoridges with low defect levels outside the trenches. This approach not only further reduces the number of defects, but also provides precise control over the size and composition of the material. Our optimized nanoridge structures typically have threading dislocation densities well below 10.⁵ cm^-2. imec has now used the III-V nanocomb development concept to demonstrate the first full-scale fabrication of electrically pumped GaAs lasers on standard 300mm diameter silicon wafers, entirely on a pilot CMOS production line,” says Bernardette Kuhnert, research scientist. director of imec.

Using low-defectivity GaAs nanoridge structures, the lasers integrate multiple InGaAs quantum wells (MQWs) as an optical gain region, embedded in an in-situ doped pin diode and passivated by an InGaP cap layer.

Achieving continuous operation at room temperature using electrical injection is a major advance, overcoming challenges in current delivery and interface design.

The devices demonstrate lasing at ~1020 nm with a threshold current as low as 5 mA, tilt efficiencies as low as 0.5 W/A, and optical power as high as 1.75 mW, demonstrating a scalable pathway for high-performance silicon light sources.

“The cost-effective integration of high-quality III-V gain materials onto large-diameter silicon wafers is key to next-generation silicon photonics applications. These exciting laser nanocomb results represent an important milestone in the use of direct epitaxial growth for monolithic III-V integration. This project is part of imec’s larger research mission to advance III-V integration processes towards higher technology readiness, from hybrid flip-chip and transfer printing methods in the near future to heterogeneous wafer-to-die bonding technologies and ultimately to direct technologies for connecting wafers and crystals. epitaxial growth in the long term,” states Joris Van Campenhout, a silicon photonics colleague and director of the industry R&D program for optical I/O at imec.