Silicon's potential breakthrough for microelectronics

Moore’s Law predicts that computers will double in their processing speed and capability every two years, which has been true until very recently. Advancements in computing have begun to slow down because silicon chips can only get so small before running into issues.

Optoelectronics may be the solution and the key to the next age of microprocessing.

The boundaries of silicon

The main reason why developments in computing technology have slowed their pace is because scientists, and companies, can’t keep shrinking silicon chips and still make a profit. The challenges that silicon microelectronics have to overcome at this stage are in the realm of flukes in quantum physics, meaning research for solutions can be slow and expensive. There are a couple of reasons why engineers can’t simply keep squeezing more into microscopic silicon chips.

Quantum tunnelling

The first hurdle is a quantum one, a phenomenon called 'quantum tunnelling'. In microelectronics, this occurs when transistors are so small and so close together that electrons occasionally pass straight through them. The Heisenberg Uncertainty Principle asserts that it is not possible to know with absolute certainty where any electron is, but physicists can still predict with reasonable certainty where an electron may end up. With quantum tunnelling, however, even this becomes virtually impossible.

Quantum tunnelling is essentially a glitch of physics. It doesn’t happen with regularity and technically breaks the laws of physics. Quantum tunnelling is a problem because those 'glitch' electrons that skip over transistors will cause a short circuit. This has become a major concern for computer scientists since it happens more frequently, or at least is likely to happen more frequently, the smaller microelectronics get.

What this means for R&D is that silicon chips can only get so small and so dense before quantum tunnelling renders them unusable. This size limitation has a ripple effect that will put the breaks on groundbreaking technological movements, such as nanotechnology.

Density and heat

The metallic connections used in today’s electronics naturally emit heat as electrons move through them. With so much power in such extremely small packages in modern silicon chips, heat is a primary concern. With everything packed so close together, microelectronics heat up more and faster the smaller they get.

This is why ultra-powerful laptops that manage to stay relatively cool are so impressive. They either have excellent heat management or superbly efficient electronics. There are some ways of improving the performance of chips, such as electroplating and optimising efficiency (Apple’s in-house silicon chips have become excellent through the latter). These fixes can certainly make a difference, but the underlying issue remains.

Heat has always been an issue with electronics, though. With technology moving towards smaller and more advanced form factors, heat will increasingly become a limiting factor in the abilities of metallic silicon. Scientists may have discovered a way of resolving this as well as quantum tunnelling, pushing the limits of silicon even further.

Silicon and optical computing

Optical computing could completely revolutionise mainstream technology. Rather than using electrons to transmit signals, diodes and lasers move photons around to complete computations. Photons can travel fairly great distances with minimal heat emissions, making optical connections ideal for replacing metallic connections. Since light travels faster than anything else in the universe, computing speeds could skyrocket using optoelectronic chips.

Photons may still be affected by quantum tunnelling, but not in the same way that electrons are. The principle is the same: light moves in waves and some wavelengths are more likely to break through physical barriers and pop out the other side, rather than bouncing off. It is slightly more predictable with photons than electrons, though, since some wavelengths do tend to be less likely to experience quantum tunnelling.

Researchers at SkolTech (the Skolkovo Institute of Science and Technology) have made substantial progress optimising silicon for optical computing. Silicon naturally has a low photoluminesce, so it doesn’t emit or absorb light well. This is not ideal for optoelectronic applications, but silicon’s semiconducting capabilities are undeniable, so many scientists are betting on improving silicon in order to make it usable for photonic integrated circuits.

The team at SkolTech was able to improve silicon’s luminescence using quantum dots and photonic crystals. Quantum dots, in this case, made of geranium, are semiconducting nanoparticles that are foundational to nanotechnology. Photonic crystals are essentially custom-designed structures that 'filter' electromagnetic waves, allowing some through but not others. A resonator was then used to contain the luminance. SkolTech’s project multiplied silicon’s luminance by over 100 times. This opens the doorway for the emergence of photonic integrated circuits and optoelectronics.

The future of electronics

The implications of optical computing are astonishing. If scientists could design silicon parts that would work with photon connections, they would be able to shrink chips down even further in size. This lends itself to the mainstream adoption of nanotechnology, which would literally change the fabric of everyday life.

Nanotech is the ultimate frontier of microelectronics: computers so small that they are invisible except under extremely powerful microscopes and virtually weightless. Physicists have proposed using nanotechnology for a wide array of applications. Nanocomputers could be sewn into fabrics to create 'smart clothes' that could monitor health data without any bulky equipment. Flexible silicon strips could be woven together to create ultra-thin electronic paper.

Outside the commercial sector, the applications for medicine and national security are groundbreaking. Scientists are researching using carbon nanotubes and nanoscale robots to treat cancer and improve the delivery of medications within the body. Meanwhile, the U.S. Department of Homeland Security has been studying the use of nanotechnology to detect explosives. Nanotech can even be used to improve the energy grid and aid in the battle against climate change.

Optical computing and beyond

Many believe the time has come to find a replacement for silicon at the top of the semiconducting food chain. However, no other element has been able to beat silicon for performance and compatibility yet. The major development in optical computing made at SkolTech is a gamechanger, and one that proves silicon is here to stay for a while longer. Optoelectronics will change technology as we know it, creating advancements in computing like never before.