The last missing piece of silicon photonics
Scientists from the Lich Research Center, the FZJ, the University of Stuttgart and the Leibniz Institute for High Performance Microelectronics (IHP), together with their French partner CEA-Leti, have developed the first cell made exclusively from group 4 of the periodic table of elements – – “Silicon Tribe”. Made from ultra-thin stacked layers of silicon germanium tin and germanium tin, the new laser is the first of its kind grown directly on a silicon wafer, opening up new possibilities for on-chip integrated photonics. The findings have been published in a scientific journal nature communications.
The rapid development of artificial intelligence (AI) and the Internet of Things (IoT) is driving the need for increasingly powerful and energy-efficient hardware. Fiber optic data transmission, capable of transmitting large amounts of data while minimizing energy loss, has become the preferred method for distances above one meter and is proving beneficial even for shorter distances. This development points to future microchips using low-cost photonic integrated circuits (PICs), which can provide significant cost savings and improved performance.
In recent years, significant progress has been made in the single-chip integration of active optical components on silicon wafers. Key components including high-performance modulators, photodetectors and waveguides have been developed. However, a long-standing challenge is the lack of high-efficiency electrical pump light sources using only Group IV semiconductors. Until now, such light sources have traditionally relied on III-V materials, which are difficult and therefore costly to integrate with silicon. This new laser fills this gap, making it compatible with traditional CMOS technology used for wafer manufacturing and suitable for seamless integration into existing silicon manufacturing processes. Therefore, it can be considered the “last missing piece” in the silicon photonics toolbox.
Researchers have demonstrated for the first time 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 only 5 milliamperes (mA) at a voltage of 2 volts (V), which is comparable to the energy consumption of a light-emitting diode. With its advanced multiple quantum well structure and ring geometry, the laser minimizes power consumption and heat generation, enabling stable operation at temperatures up to 90 Kelvin (K), or minus 183.15 degrees Celsius (°C) .
Grown on standard silicon wafers (such as those used for silicon transistors), it represents the first truly “usable” Group IV laser, but requires further optimization to further reduce the laser threshold and enable room temperature operation. . However, a clear path forward was shown by the success of early optically pumped germanium-tin lasers, which went from cryogenic to room-temperature operation in just a few years.
In optically pumped lasers, an external light source is required to generate laser light, whereas in electrically pumped lasers, light is generated when an electric current is passed through a diode. Electrically pumped lasers are generally more energy efficient because they convert electrical energy directly into laser light.
The research group, led by Dr. Buca from the Research Center PGI-9 in Lich, has been working on the development of tin-based Group IV alloys for many years in collaboration with partners such as IHP, University of Stuttgart, CEA-Leti, C2N-Université Paris-Sud and Politecnico di Milano. They have already demonstrated potential for applications in photonics, electronics, thermoelectrics and spintronics. With this new achievement, silicon photonics’ vision of providing integrated solutions for the next generation of microchips is now a reality.
2024-12-09 17:27:46