III-V Lasers Grown on Silicon Wafers Could Advance Silicon Photonics

Researchers from the Hong Kong University of Science and Technology (HKUST) have directly grown 1.5-μm III-V lasers on industry-standard 220-nm silicon-on-insulators (SOI) wafers without buffer. This work could advance the use of III-V light sources with silicon (Si)-based photonic devices.

In conventional approaches to integrating III-V lasers on Si, III-V buffers up to a few μm thick are applied to reduce the defect densities. The thickness of these buffers can make the interface between the III-V lasers and the Si-based waveguides less efficient. The HKUST team devised a growth scheme that eliminates the need for thick III-V buffers to allow more efficient light coupling into the Si-waveguides.

The group led by professor Lau Kei-May used metal organic chemical vapor deposition to grow the III-V lasers on SOI wafers. This approach featured epitaxy inside trapezoidal troughs to enable the flexible integration of different III-V compounds on SOIs with different Si device layer thicknesses. The researchers characterized the crystalline quality of these III-V materials through photoluminescence measurements and extensive use of transmission electron microscopy.

Schematic of III-V laser array directly grown on Si-photonic 220-nm SOI platform. Courtesy of HKUST.

The team designed and fabricated the air-cladded laser cavities based on numerical simulations. Tests showed that the lasers could sustain room-temperature and low-threshold lasing in the technologically important 1.5-μm band under pulsed optical excitation.

The work by the HKUST researchers could make it possible to monolithically integrate III-V lasers on industry-standard 220-nm SOI wafers in an economical, compact, scalable way.

“If practically applied, our technology could enable a significant improvement of the speed, power consumption, cost-effectiveness, and functionality of current Si-based integrated circuits,” professor Lau said. “Our daily electronic devices, such as smartphones, laptops, and TVs — basically everything connected to the internet — will be much faster, cheaper, using much less power and [will be] multifunctional.”

Researcher Han Yu said that the next step will be to design and demonstrate the first electrically driven 1.5-μm III-V lasers directly grown on the 220-nm SOI platforms, and devise a scheme to efficiently couple light from the III-V lasers into Si-waveguides to conceptually demonstrate fully integrated Si-photonics circuits.

The research was published in Optica, a publication of OSA, The Optical Society. (www.doi.org/10.1364/OPTICA.381745).