FOCUS RESEARCH NEWS TUM physicists deposit nano-lasers onto silicon chips
Scientists have developed a process to deposit nano-lasers directly onto silicon chips, paving the way for fast and efficient data processing using silicon photonics. Physicists at the Technical
University of Munich (TUM) have developed a nano-laser one thousand times thinner than a human hair. This process deposits the nano-wire lasers directly onto the chip, making it possible to produce high-performance, cost- effective photonic components. Data transmission and processing with light has the potential for breaking the barriers of current electronics. The first silicon-based photonics chips already exist. However, the sources of light for the transmission of data must be attached to the silicon using complicated and elaborate manufacturing processes. The researchers from TU Munich
developed a process of depositing nano-lasers directly onto silicon chips – alleviating the increased costs associated with making smaller transistors. A patent for the technology is pending. Traditionally, growing a III-V semiconductor (such as gallium- arsenide) on silicon requires complicated and time-consuming development that has restricted its use in commercial applications. ‘The two materials have different lattice parameters and different coefficients of thermal expansion. This leads to strain,’ explained Dr Gregor Koblmüller who led the team at TUM. ‘For example, conventional planar growth of gallium arsenide onto a silicon surface results in a large number of defects.’
The TUM team solved this problem by depositing freestanding nano-wires, with a footprint of only a few nanometres, directly onto the silicon substrate. This process helped the scientists to reduce defects associated with the production of GaAs
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semiconductors. The next step for the project was to convert the nano-wire into a vertical-cavity laser.
‘The interface between gallium
arsenide and silicon does not reflect light sufficiently. We thus
built in an additional mirror – a 200nm silicon oxide layer that we evaporated onto the silicon,’ said Benedikt Mayer, doctoral candidate in the team. ‘Tiny holes can then be etched into the mirror layer. Using epitaxy, the semiconductor
nano-wires can then be grown, atom for atom, out of these holes.’ ‘We want to create an electric interface so that we can operate the nano-wires under electrical injection, instead of relying on external lasers,’ stated Koblmüller.
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