Lab talk
Apr 28, 2008
Encoding information in light from silicon quantum dots
Silicon technology has allowed a dramatic increase of the microelectronics industry over the past three decades. Unfortunately, the end of the road for this technology has clearly come into view. Silicon photonics is the technology of signal processing, transmission and detection where the signal is carried by photons (light), all integrated into silicon chips. It promises to solve many of the challenges imposed by present-day electrical circuits and interconnects because of the favourable physics governing optical processing and signalling.
In a recent work, published in Nanotechnology 19 205201, the authors studied the mechanisms that make possible the direct modulation of light from silicon quantum dots integrated into a MOSFET transistor. The physical principle of modulation is based on the inability of silicon quantum dots to emit light when they are in a charged state, basically due to a reinforcement of the non-radiative paths.
J Carreras et al. have been able to modulate light from silicon nanocrystals at rates of 200 Mbit/s by using boosted electrons from channels to charge the nanocrystals. The main advantages to conventional modulators include less current consumption (from the theoretical minimum of 104 A cm–2 in p-i-n modulators to 1 A cm–2 in the presented device), extremely low modulating voltages (1 V for modulation depths close to 100%) and inherent scalability.
Other interesting applications may be envisaged from the principle of high-speed control of luminescence in ultra-scaled MOSFETs, such as integrated biological sensing or single photon-on-demand emitters.
About the author
Josep Carreras (Barcelona, 1977) is currently a contracted researcher at the Department of Electronics, University of Barcelona. His research interests include new concepts of devices based on silicon quantum dots for silicon photonics, for non-volatile memory applications, as well as the study of transport through low-dimensional systems.
