27 October 2017 2D materials for all optical communication on silicon chips


A study from MIT in collaboration with ICFO reports on a new MoTe2-based detector and emitter for silicon photonic integrated circuits. The rapid advancement of technologies is imposing a constant need to miniaturize devices. However, one of the major drawbacks in trying to shrink circuit components down means that you can only shrink things down up to a certain size. In trying to push the limits, the overlapping of signals and currents diminishes the inter-chip communication speeds quite drastically, an effect that is known as the "bottleneck".

In optoelectronics, on-going research has been aiming for ways to improve optical on-chip communications microelectronics. Now, electronic circuits are mainly based on silicon; however silicon-based technologies are beginning to show certain limitations with the new demands of optical communications technologies because silicon is a bad light emitter. Not only is it a bad light emitter, it also emits outside the visible range, it is bulky, rigid, and is not compatible with most other materials.

While searching for new materials that could merge optoelectronics and optical on-chip communication and improve silicon photodetectors, the emerging two-dimensional transition-metal dichalcogenides (TMDs) offer a path for optical interconnectivity that can be easily integrated with silicon photonics and CMOS technologies.

In a recent paper published in Nature Nanotechnology, selected as a Nature News and Views piece and highlighted in a MIT News article, researchers from MIT in USA in collaboration with ICFO Prof. Dmitri Efetov, have now been able to demonstrate a silicon waveguide-integrated light source and photodetector based on a p-n junction of bilayer molybdenum ditelluride (MoTe2) that can perform in the infrared range, where silicon does not absorb light.

In their experiment, they took a MoTe2 2D layer and created a semiconductor diode to achieve emission of light, Here they discovered that it was not necessary to introduce chemical impurities to create the p-n junction properties, but rather only needed to apply a voltage across the material to make it emit or detect light, depending on the polarity of the current. They saw that the MoTe2-silicon device was able to emit and detect infrared light at a frequency range where silicon is not absorptive, and hence were able to perform communication protocols through silicon wave-guides.

The results of this study show that this state-of-the-art fabrication technology provides new opportunities for integrated optoelectronic systems. This study has demonstrated that this 2D material is completely compatible with Si-CMOS technology and could offer many advantages for on-chip optical communications with much higher performance and a broader spectrum of functionalities.