Imec, a leading research and innovation hub, has made a breakthrough in the field of silicon photonics with the successful demonstration of electrically-driven GaAs-based multi-quantum-well nano-ridge laser diodes. These innovative devices have been fully fabricated on 300 mm silicon wafers within Imec's CMOS pilot prototyping line, marking a significant milestone in the ongoing development of advanced photonics technology. The findings were published last week in the prestigious journal Nature.
The key achievement of this research lies in the direct epitaxial growth of high-quality III-V materials on silicon, yielding room-temperature continuous-wave lasing with notably low threshold currents of just 5 mA and output voltages that exceed 1 mW. Such developments are particularly relevant for industries focusing on artificial intelligence (AI), machine learning, and data communications, as they pave the way for the creation of cost-effective optical devices tailored for these applications.
Historically, the proliferation of silicon photonics has faced challenges largely due to the unavailability of native CMOS-integrated light sources that offer scalability. Existing solutions such as hybrid or heterogeneous integration techniques—including die-to-wafer bonding, micro-transfer printing, and flip-chip—are often complicated and costly. These methods typically depend on III-V substrates, which are frequently discarded post-processing, raising concerns about resource efficiency and sustainability across the industry.
A major hurdle in this domain has been the formation of crystal misfit defects, which arise from the significant thermal expansion coefficient discrepancies and crystal lattice parameter differences between III-V materials and silicon. These defects can adversely impact the reliability and overall performance of lasers. Imec has tackled this issue by employing a selective-area growth (SAG) technique combined with aspect-ratio trapping (ART). This innovative approach effectively confines misfit dislocations within narrow trenches etched into a dielectric mask, thereby significantly reducing defects in the integrated III-V materials on silicon wafers.
The newly designed nano-ridge lasers utilise low-defectivity GaAs structures to incorporate InGaAs multiple quantum wells (MQWs), which serve as the active optical gain region. This configuration is complemented by an in-situ doped p-i-n diode and a passivating InGaP capping layer. Achieving continuous-wave operation at room temperature through electrical injection represents a notable advancement, addressing previous challenges associated with interface engineering and effective current delivery. The devices demonstrate lasing capabilities at approximately 1020 nm, with some operating at threshold currents as low as 5 mA, slope efficiencies reaching 0.5 W/A, and optical powers nearing 1.75 mW, indicating a promising direction for scalable high-performance silicon-integrated light sources.
As a result of these advancements, the potential applications in various sectors—particularly those reliant on optical communication technologies—are set to grow, driven by inexpensive and efficient light sources that leverage silicon’s established manufacturing infrastructure.
Source: Noah Wire Services