Silicon photonic circuits are revolutionizing various applications, from data centers to biosensors and lidar. However, integrating lasers directly onto silicon chips has been challenging due to material incompatibility. Silicon cannot efficiently generate laser light, and traditional laser materials like gallium arsenide (GaAs) suffer from crystal defects when grown on silicon. Researchers have developed a novel technique to overcome this hurdle. Using standard fabrication processes, they’ve demonstrated the growth of GaAs lasers directly on 300mm silicon wafers. Instead of direct growth, they create trenches in silicon dioxide on the wafer and deposit GaAs within these trenches, contacting silicon only at the trench bottom.
This confines the resulting crystal defects within the trench, preventing them from propagating into the active laser region. Subsequent GaAs laser growth along nanoscale ridges, incorporating indium gallium arsenide, forms the laser structure. Electrical contacts and mirrors complete the device.
This innovative approach allows for scalable and cost-effective production of photonic circuits. They have successfully fabricated hundreds of these nanoridge lasers and photodetectors on a single 300mm wafer. While the current lasers operate at 1020nm, the team is working on extending the wavelength for telecommunications applications. They are also addressing reliability issues related to contact-induced defects. This breakthrough can potentially transform silicon photonics by enabling seamless laser integration.
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