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Researchers have created the first Group IV electrically pumped laser, overcoming key challenges in silicon photonics. Operating with low power on silicon wafers, it promises efficient, cost-effective solutions for next-generation microchips. Credit: Forschungszentrum Jülich / Jhonny Tiscareno
International research team unveils the first electrically pumped continuous-wave semiconductor laser designed for seamless integration with silicon.
Scientists from Forschungszentrum Jülich (FZJ), the University of Stuttgart, the Leibniz Institute for High Performance Microelectronics (IHP), and their French partner CEA-Leti have successfully developed the first electrically pumped continuous-wave semiconductor laser made entirely from group IV elements, commonly referred to as the “silicon group” in the periodic table.
This innovative laser is constructed from stacked ultrathin layers of silicon-germanium-tin and germanium-tin. Remarkably, it is the first laser of its type to be directly grown on a silicon wafer, paving the way for advancements in on-chip integrated photonics. The research findings have been published in the prestigious journal Nature Communications.
Growing Demand for Energy-Efficient Photonics
The rapid growth of artificial intelligence (AI) and the Internet of Things (IoT) are driving the demand for increasingly powerful, energy-efficient hardware. Optical data transmission, with its ability to transfer vast amounts of data while minimizing energy loss, is already the preferred method for distances above one meter and is proving advantageous even for shorter distances.
Schematic view of the new laser. Credit: Forschungszentrum Jülich / Jhonny Tiscareno
This development points towards future microchips featuring low-cost photonic integrated circuits (PICs), offering significant cost savings and improved performance.
In recent years, significant progress has been made in monolithically integrating optically active components on silicon chips. Key components, including high-performance modulators, photodetectors, and waveguides have been developed. However, a long-standing challenge has been the lack of an efficient, electrically pumped light source using only Group IV semiconductors.
Until now, such light sources have traditionally relied on III-V materials, which are difficult and therefore expensive to integrate with silicon. This new laser addresses that gap, making it compatible with the conventional CMOS technology for chip fabrication and suitable for seamless integration into existing silicon manufacturing processes. It could therefore be seen as the “last missing piece” in the silicon photonics toolbox.
Key Innovations in the New Laser
For the first time, the researchers have demonstrated continuous-wave operation in an electrically pumped Group IV laser on silicon. Unlike previous germanium-tin lasers that relied on high-energy optical pumping, this new laser operates with a low current injection of just 5 milliamperes (mA) at 2 volts (V), comparable to the energy consumption of a light-emitting diode.
With its advanced multi-quantum well structure and ring geometry, the laser minimizes the power consumption and the heat generation, enabling stable operation up to 90 Kelvin (K) or minus 183.15 degrees Celsius (°C).
Scanning electron micrograph. Credit: Forschungszentrum Jülich / Jhonny Tiscareno
Grown on standard silicon wafers like those used for silicon transistors, it represents the first truly “usable” Group IV laser, though further optimizations are needed to further reduce the lasing threshold and achieve room-temperature operation. However, the success of earlier optically pumped germanium-tin lasers, which have evolved from cryogenic to room-temperature operation in only a few years, suggests a clear path forward.
In an optically pumped laser, an external light source is required to generate the lasing light, while the electrically pumped laser generates light when an electrical current is passing through the diode. Electrically pumped lasers are usually more energy-efficient as they directly convert electricity directly into laser light.
Reference: “Continuous-wave electrically pumped multi-quantum-well laser based on group-IV semiconductors” by Lukas Seidel, Teren Liu, Omar Concepción, Bahareh Marzban, Vivien Kiyek, Davide Spirito, Daniel Schwarz, Aimen Benkhelifa, Jörg Schulze, Zoran Ikonic, Jean-Michel Hartmann, Alexei Chelnokov, Jeremy Witzens, Giovanni Capellini, Michael Oehme, Detlev Grützmacher and Dan Buca, 3 December 2024, Nature Communications.
DOI: 10.1038/s41467-024-54873-z
The research group, led by Dr. Buca from Forschungszentrum Jülich’s PGI-9, has been pioneering tin-based Group IV alloys for years, collaborating with partners such as IHP, the University of Stuttgart, CEA-Leti, C2N-Université Paris-Sud, and Politecnico di Milano. They have already demonstrated the potential for applications in photonics, electronics, thermoelectric, and spintronics. With this new achievement, the vision of silicon photonics providing an all-in-one solution for next-generation microchips is now within reach.
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