Light-emitting silicon overcomes a major obstacle to denser, faster chips
Breakthrough after 50 years of work paves the way for photonic chipsValentina Spiridonova
The push for ever-smaller chips has been running into more and more obstacles, including the very limits of silicon - while optical connections would allow for denser, speedier processors by eliminating heat and energy issues, silicon is lousy at emitting light. Or rather, it was.
Eindhoven University of Technology researchers have developed what they say is the first silicon alloy that can emit light. The breakthrough is a mix of silicon and germanium in a hexagonal structure that allows a band gap (and thus emitting light).
Emitting light from silicon has been the 'Holy Grail' in the microelectronics industry for about 50 years. In contrast to electrons, photons do not experience resistance. As they have no mass or charge, they will scatter less within the material they travel through, and therefore no heat is produced. The energy consumption will therefore be reduced. Moreover, by replacing electrical communication within a chip by optical communication, the speed of on-chip and chip-to-chip communication can be increased by a factor 1000. To use light in chips, you will need a light source; an integrated laser. The main semiconductor material that computer chips are made of is silicon. But bulk silicon is extremely inefficient at emitting light, and so was long thought to play no role in photonics. Thus, scientists turned to more complex semiconductors, such as gallium arsenide and indium phosphide. These are good at emitting light but are more expensive than silicon and are hard to integrate into existing silicon microchips.
To create a silicon compatible laser, scientists needed to produce a form of silicon that can emit light. That's exactly what researchers from Eindhoven University of Technology (TU/e) now succeeded in. The team created hexagonal silicon back in 2015. However, they couldn’t get the result to emit light until now, when they reduced the number of impurities and defects.
The team still needs to produce a laser before they have technology that could be used in chips, and there would still be plenty of refinement left before you would see this in shipping electronics. That laser is expected in 2020, though. And this latest development was arguably the largest hurdle. From now on, the main challenge is making the technology practical.
Solving this puzzle promises a revolution in computing, as chips will become faster than ever. Data centers would benefit most, with faster data transfer and less energy usage for their cooling system. But these photonic chips will also bring new applications within reach. Think of laser-based radar for self-driving cars and chemical sensors for medical diagnosis or for measuring air and food quality.