New germanium-tin laser could replace copper wire for data transfers


One of the major challenges of reducing modern day semiconductor power consumption has been our reliance on copper wire for data transfers. Past a certain point, copper simply doesn’t work well — it’s size can only scale to a certain point (which we’ve mostly reached), and past a certain point, making wires smaller also raises their electrical impedance. This means you end up with a higher level of resistance inside the chip, and resistance translates directly into higher heat. Now, scientists have demonstrated a new laser technique that can transfer data far more efficiently using a germanium-tin laser.

Laser-based data transfer has been a holy grail for the interconnect business for years. As wires become smaller, it also becomes more difficult to lay them properly — we actually covered a new technique for depositing copper inside a chip last year — but such manufacturing tricks are taking longer to develop and offer less scaling than they used to. The ability to move data using light doesn’t just offer a huge potential performance boost, it could also dramatically reduce power consumption. According to Professor Detlev Grützmacher, clock signals consume more than 30% of the energy required to move data inside a modern processor — which gives some idea of just how much power could be saved long term.

Silicon photonics and laser types

This new germanium-tin laser is different from the silicon photonics research that Intel has been researching for the past decade. Most obviously, it doesn’t rely on silicon or the heterogeneous integration of III-V lasers built on a silicon substrate.


One of the problems with silicon photonics is that silicon has no direct band gap, meaning it has no native way to emit light. One of the chief goals of silicon photonics research is ton continue to reduce this power consumption, with the eventual goal of cutting power per bit to a fraction of its current level. The germanium-tin laser this research group utilized offers a potentially lower costs and far easier integration into existing CMOS assembly. The one caveat, however, is the temperature — at present, the germanium-tin solution requires an operating temperature of -183 degrees Celsius. That severely limits applications, even if all the other problems were solved — you need liquid helium to maintain an operating temperature of -183 degrees Celsius, and you need a lot of it.


For now, these requirements are going to limit the usefulness of alternative laser methods and data transfer options — but if these techniques can be translated to hardware that can operate at room temperature, they could speed the adoption of optical interconnects in the long term. Silicon photonics is currently mostly intended for high-end enterprise deployments — Intel has given no information on when it might bring this technology to consumer hardware, or how it would integrate it within the CPU die.