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08.04.2020 – 17:38

Technische Universität München

A new light source for the chip industry: light-emitting silicon-germanium alloys


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A new light source for the chip industry

Photonic chips made possible by light-emitting silicon-germanium alloys

For the past 50 years, researchers around the globe have been looking for a way to make lasers with silicon or germanium. A team from the Technical University of Eindhoven (TU/e) and the Technical University of Munich (TUM) has now succeeded in developing light-emitting, silicon-germanium alloys. As a result, the development of a silicon laser capable of integration into today's chips is within reach for the first time.

Electronic chips produce heat when processing data. The laptop starts to feel uncomfortably hot on the user's knees; data centers need energy-hungry cooling equipment. The solution may lie in the field of photonics – because light pulses do not emit heat.

For the past half century, this insight has driven efforts by researchers to build silicon or germanium-based lasers – so far in vain. Silicon, the workhorse of the chip industry, normally crystallizes in a cubic crystal lattice. In this form it is not suitable for converting electrons into light.

Together with colleagues from the Technical University of Munich and the universities in Jena and Linz, researchers at the Technical University of Eindhoven have now developed alloys made of germanium and silicon capable of emitting light.

The crucial step was the ability to produce germanium and alloys from germanium and silicon with a hexagonal crystal lattice. “This material has a direct band gap, and can therefore emit light itself,” says Prof. Jonathan Finley, Professor of Semiconductor Quantum Nanosystems at TUM.

The template trick

Prof. Erik Bakkers and his team at TU Eindhoven first produced hexagonal silicon back in 2015. They started by growing a hexagonal crystal structure with nanowires made of another material. This served as a template for a germanium-silicon shell on which the underlying material imposed its hexagonal crystal structure.

Initially, however, these structures could not be stimulated to emit light. Through the exchange of ideas with colleagues at the Walter Schottky Institute at the Technical University of Munich, who analyzed the optical characteristics with each successive generation, the production process was finally optimized to a grade of perfection where the nanowires were indeed capable of emitting light.

“In the meantime, we have achieved properties almost comparable to indium phosphide or gallium arsenide,” says Prof. Bakkers. As a result, it appears to be just a matter of time before a laser made from germanium-silicon alloys and capable of integration into conventional production processes is developed.

“If we can implement on-chip and inter-chip electronic communications by optical means, speeds can be increased by a factor of up to 1,000,” says Jonathan Finley. “In addition, the direct combination of optics and electronics could drastically reduce the cost of chips for laser-based radar in self-driving cars, chemical sensors for medical diagnostics, and air and food quality measurements.”


Direct Bandgap Emission from Hexagonal Ge and SiGe Alloys

E. M. T. Fadaly, A. Dijkstra, J. R. Suckert, D. Ziss, M. A. J. v. Tilburg, C. Mao, Y. Ren, V. T. v. Lange, S. Kölling, M. A. Verheijen, D. Busse, C. Rödl, J. Furthmüller, F. Bechstedt, J. Stangl, J. J. Finley, S. Botti, J. E. M. Haverkort, E. P. A. M. Bakkers.

Nature, 8. April 2020 – DOI: 10.1038/s41586-020-2150-y


Further information:

The research project received funding from the European Union (EU) project, SiLAS, the Marie Sklodowska Curie Programme of the EU, the Dutch Research Council (NWO), the Solliance Initiative of the Energy research Centre of the Netherlands (ECN), the Holst Center, the TU/e, the Netherlands Organization for Applied Scientific Research (TNO), the Interuniversity Microelectronics Centre (IMEC), the Forschungszentrum Jülich and the province of North Brabant in the Netherlands. The Deutsches Elektronen Synchrotron (DESY) in Hamburg provided measurement time on the PETRA III facility. Theoretical calculations were carried out on the SuperMUC high-performance computer at the Leibniz Supercomputing Center in Garching, Germany.

High resolution images:


Prof. Dr. Jonathan J. Finley

Walter Schottky Institute and Physics Department

Technical University of Munich

Am Coulombwall 4, 85748 Garching, Germany

Tel.: +49 89 289 12770 – e-mail:

The Technical University of Munich (TUM) is one of Europe’s leading research universities, with around 600 professors, 43,000 students, and 10,000 academic and non-academic staff. Its focus areas are the engineering sciences, natural sciences, life sciences and medicine, combined with economic and social sciences. TUM acts as an entrepreneurial university that promotes talents and creates value for society. In that it profits from having strong partners in science and industry. It is represented worldwide with the TUM Asia campus in Singapore as well as offices in Beijing, Brussels, Cairo, Mumbai, San Francisco, and São Paulo. Nobel Prize winners and inventors such as Rudolf Diesel, Carl von Linde, and Rudolf Mößbauer have done research at TUM. In 2006, 2012 and 2019 it won recognition as a German "Excellence University." In international rankings, TUM regularly places among the best universities in Germany.

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