Skoltech researchers and their colleagues from RAS Institute for Physics of Micro­structures, Lobachevsky State University of Nizhny Novgorod, ITMO University, Lomonosov Moscow State University, and A.M. Prokhorov General Physics Institute have found a way to increase photo­luminescence in silicon, the notoriously poor emitter and absorber of photons at the heart of all modern electronics. This discovery may pave the way to photonic integrated circuits, boosting their performance.

Natural selection& in semi­conductor technology over almost 80 years has led to silicon emerging as the predominant material for chips. Most digital micro­circuits are created using CMOS technology. Yet manu­facturers have hit a wall on the way to increasing their per­formance even further: heat release due to high density of elements in CMOS circuits. One potential workaround is reducing heat generation by switching from metallic connec­tions between elements in micro­circuits to optical ones. “The transition to CMOS-compatible photonic inte­grated circuits will also make it possible to signi­ficantly increase the information transfer rate within a chip and between individual chips in modern computers, making them faster. Unfor­tunately, silicon itself weakly interacts with light: it is a poor emitter and a poor absorber of photons. Therefore, taming silicon to interact with light effectively is an essential task,” Sergey Dyakov, senior researcher at Skoltech says.

Dyakov and his colleagues have managed to enhance silicon-based photo­luminescence using germanium quantum dots and a specially designed photonic crystal. They used a resonator based on bound states in the continuum, an idea borrowed from quantum mechanics: these resonators create effective confinement of light inside them since the symmetry of the electro­magnetic field inside the resonator does not correspond to the symmetry of the electro­magnetic waves of the surrounding space. They also chose germanium nanoislands as a source of luminescence, which can be embedded into the desired place on a silicon chip. “The use of bound states in the continuum increased luminescence intensity by more than a hundred times,” Dyakov says, noting that it can lead us to CMOS-compa­tible photonic inte­grated circuits.

“The results open up new possi­bilities for creating efficient radiation sources based on silicon, built into the circuits of modern micro­electronics with optical signal processing. There are currently lots of groups working on creating light-emitting diodes based on such structures and the principles of their coupling with other elements on an opto­electronic chip,” Nikolay Gippius, head of Nanophotonics Theory group at the Center of Photonics and Quantum Materials at Skoltech, says. (Source: Skoltech)

Reference: S. A. Dyakov et al.: Photonic Bound States in the Continuum in Si Structures with the Self-Assembled Ge Nanoislands, Laser & Phot. Rev., online 3 June 2021; DOI: 10.1002/lpor.202000242

Link: Center of Photonics and Quantum Materials, Skolkovo Institute of Science and Technology, Moscow, Russia