UCL announces silicon photonics breakthrough

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UK researchers have provided the first demonstration of an electrically driven, quantum dot laser grown directly on a silicon substrate (Si) with a wavelength suitable for use in telecommunications – 1300nm.

A team from University College London has announced the breakthrough which could bring a new generation of high speed, silicon based information technology a step closer. As the speed and complexity of silicon electronics increases, the field of silicon photonics addresses the problem of interconnecting large information processing systems. The ideal light source for silicon photonics is a semiconductor laser and, to date, the most promising solution has been the use of wafer bonding to join compound semiconductor laser materials, from which lasers can be made to a silicon substrate. The most attractive route to full integration for silicon photonics would be direct growth of semiconductor laser material on silicon. However, the large differences in crystal lattice constant between silicon and compound semiconductors cause dislocations in the crystal structure that result in low efficiency and short operating lifetime for semiconductor lasers. The UCL group says it has overcome these difficulties by developing special layers which prevent these dislocations from reaching the laser layer together with a quantum dot laser gain layer. This has enabled them to demonstrate an electrically pumped 1300nm wavelength laser by direct epitaxial growth on silicon. Professor Alwyn Seeds, head of the Photonics Group in the UCL Department of Electronic and Electrical Engineering, said: "The techniques that we have developed permit us to realise the Holy Grail of silicon photonics - an efficient, electrically pumped, semiconductor laser integrated on a silicon substrate. Our future work will be aimed at combining these lasers with waveguides and drive electronics leading to a comprehensive technology for the integration of photonics with silicon electronics." The research will be published in Nature Photonics.