Researchers at Forschungszentrum Jülich (FZJ), the University of Stuttgart, the Leibniz Institute for High Performance Microelectronics (IHP), and their French partner CEA-Leti have achieved a breakthrough by developing the first electrically pumped continuous-wave semiconductor laser composed exclusively of group-IV elements, commonly referred to as the "silicon group."
Schematic view of the new laser. Image Credit: Forschungszentrum Jülich / Jhonny Tiscareno
The growing adoption of artificial intelligence (AI) and the Internet of Things (IoT) has intensified the need for more powerful and energy-efficient hardware solutions. Optical data transmission, which enables high-capacity data transfer with minimal energy loss, is already the preferred choice for distances over one meter and is increasingly beneficial for shorter ranges. This trend highlights the potential of future microchips incorporating cost-effective photonic integrated circuits (PICs), which promise enhanced performance and reduced costs.
Recent advancements have focused on the monolithic integration of optically active components directly onto silicon chips. Critical elements such as high-performance modulators, photodetectors, and waveguides have been successfully developed. However, creating an efficient, electrically pumped light source made exclusively from Group IV semiconductors has remained a significant challenge.
Traditionally, light sources have relied on III-V materials, which are challenging and costly to integrate with silicon. This new laser overcomes that barrier, aligning with conventional CMOS technology and enabling seamless integration into established silicon manufacturing processes. It represents a transformative development, potentially filling the "final gap" in the silicon photonics ecosystem.
We have been exploring the fascinating possibilities of germanium-tin (GeSn) alloys for almost a decade. The development of an efficient, electrically pumped laser has been one of our major goals from the very beginning. This breakthrough is further proof of the enormous potential of the GeSn alloys for different applications, in this specific case for photonic applications.
Dr. Dan Buca, Group Leader, Forschungszentrum Jülich
For the first time, researchers have demonstrated continuous-wave operation in an electrically pumped Group IV laser on silicon.
Unlike earlier germanium-tin lasers that relied on high-energy optical pumping, this 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. Its advanced multi-quantum well structure and ring geometry reduce power consumption and heat generation, enabling stable operation up to 90 Kelvin (K) or minus 183.15 degrees Celsius (°C).
Grown on standard silicon wafers used for silicon transistors, it marks the first truly "usable" Group IV laser, though further optimizations are required to lower the lasing threshold and achieve room-temperature operation. The success of previous optically pumped germanium-tin lasers, which progressed from cryogenic to room-temperature operation within a few years, suggests a promising path forward.
Optically pumped lasers require an external light source to generate lasing, while electrically pumped lasers produce light through an electrical current passing through the diode. Electrically pumped lasers are generally more energy-efficient, directly converting electricity into laser light.
The research group, led by Dr. Buca of Forschungszentrum Jülich’s PGI-9, has been pioneering tin-based Group IV alloys for years in collaboration with partners including IHP, the University of Stuttgart, CEA-Leti, C2N-Université Paris-Sud, and Politecnico di Milano. This achievement brings the vision of silicon photonics as an all-in-one solution for next-generation microchips closer to reality.
Journal Reference:
Seidel, L. et. al. (2024) Continuous-wave electrically pumped multi-quantum-well laser based on group-IV semiconductors. Nature Communications. doi.org/10.1038/s41467-024-54873-z