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Physics Chat

Selective confined epitaxy of III-V nanostructures on silicon for advanced photonic devices

Speaker: Cristian Messina (QLi)
Date: Friday 24 September 2021
Time: 15:00
Venue: Zoom

Over the last decade, the rapid expansion of the Internet of Things has led to a huge increase in worldwide data exchange, with the global IP traffic exceeding the Zettabyte for the first time in 2016. As data centers struggle to keep up with the demand, new technologies have been investigated in order to achieve faster, larger and more energy efficient data transmission. While many core components for photonic integrated circuits, such as Si-based waveguides and detectors, can be readily achieved, the realization of a reliable on-chip light source remains a challenge due to the indirect bandgap of Si. Direct bandgap III-V material compounds have been widely reported as efficient light emitters, achieving high performances due to the low carrier effective mass and high mobility. However, III-V lasers are currently integrated on Si wafers by means of wafer-bonding techniques, which lead to poor electrical and thermal characteristics and require use of expensive III-V wafers. Proper monolithic integration otherwise remains a challenge because of the high lattice mismatch between III-V materials and Si, which induces the formation of crystal defects and in turn hinders the performance of a laser device by creating pathways of non-radiative recombination for the carriers. Epitaxy of III-V nanowires has been proposed as a solution to this challenge, since the small contact area between the Si substrate and the nanowire limits the stress buildup. Nanowires can also act as waveguides, providing high optical confinement thanks to the atomically smooth sidewalls. Moreover, with the use of patterned Si substrates, nanowires can be arranged into photonic crystal structures to achieve high cavity quality factors and engineer emerging technologies such as band-edge lasers and topological lasers.

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