«These values demonstrate that a germanium-tin laser is technologically feasible and that its efficiency matches that of conventional III-V semiconductor lasers grown on Si. This produces so little waste heat that this laser is the first group IV semiconductor laser that can be operated not only in a pulsed regime but also in a continuous working regime, i.e. «We thus tried to reduce the concentration of tin and compensate this by additionally stressing the material, which considerably improves the optical properties.»įor the new laser, the researchers reduced the tin content to approximately 5 % - and simultaneously decreased the necessary pumping power to 0.8 kW/cm2. At 12-14 % tin, we already need 100-300 kW/cm2,» explains Nils von den Driesch. The laser then requires a relatively high pumping power. «A high tin content, however, decreases the laser efficiency. By further increasing the tin concentration, lasers have already been made that work not only at low temperatures but also at 0☌. The patented epitaxial growth process developed by Jülich is used by several research groups all over the world. Dan Buca, working group leader at Jülich’s Peter Grünberg Institute (PGI-9). The high concentration of tin is what turns it into a direct semiconductor for a laser source,» explains Dr. «Pure germanium is, by its nature, an indirect semiconductor like silicon. The decisive factor in this is the high tin content: back then, it amounted to 12 %, which is far above the solubility limit of 1 %. Back in 2015, Jülich researchers showed that laser emission can be obtained in GeSn system.
It is based on germanium and tin, two group IV elements like silicon. In contrast, the new laser can be manufactured during the CMOS production process. Laser components are currently manufactured externally and must be integrated subsequently, which makes the technology expensive,» explains Grützmacher.
«Their crystal lattice, however, has a completely different structure than that of silicon, which is a group IV element. Generally, III-V compound semiconductors are used instead. Different materials are currently used for manufacturing lasers. «Such a laser could then simply be shaped during the chip manufacturing process since the entire chip production is ultimately based on this technology.»īut there is one problem: pure silicon is an «indirect semiconductor» and, therefore, unsuitable as a laser material. Detlev Grützmacher, director at Forschungszentrum Jülich’s Peter Grünberg Institute (PGI-9). An electrically pumped laser compatible with the silicon-based CMOS technology would be ideal,» explains Prof. «The most crucial missing component is a cheap laser, which is necessary to achieve high data rates. This applies particularly to artificial intelligence (AI) systems where large data volumes must be transferred within a large network in order to train the chip and the algorithms. In future, optic solutions will be in demand for shorter and shorter distances due to increasing requirements, for example board to board or chip to chip data transfer. Computation and data centres, therefore, already default to optical fiber whenever cables exceed a length of about one metre. Optical data transfer permits much higher data rates and ranges than current electronic processes while also using less energy.
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