Building better infrared sensors | ScienceDaily

Researchers at Aalto University have developed a new infrared photodiode that responds 35% faster at 1.55 µm, a key wavelength for telecommunications, compared to other germanium-based components. Importantly, this new device can be manufactured using current production techniques, making it highly practical.

“It took us eight years to go from idea to proof of concept,” says Aalto University professor Hele Savin.

The basic idea is to use germanium instead of indium gallium arsenide to make photodiodes. Germanium photodiodes are cheaper and already fully compatible with semiconductor manufacturing processes—but so far, they have performed poorly at capturing infrared light.

Savin’s team succeeded in creating germanium photodiodes that capture nearly all infrared light that hits them.

“The high performance is achieved by combining several novel approaches: using surface nanostructures to eliminate optical losses and minimizing electrical losses in two different ways,” explains Hanchen Liua doctoral researcher who built a proof-of-concept device.

The team’s tests showed that their proof-of-concept photodiode not only outperforms existing germanium photodiodes in terms of responsivity, but also outperforms commercial indium gallium arsenide photodiodes. The new technology captures infrared photons very efficiently and works well over a wide range of wavelengths. The new photodiodes can be easily fabricated through existing manufacturing facilities, and the researchers expect they can be directly integrated into many technologies.

“The timing couldn’t be better. Many fields now rely on sensing infrared radiation, and the technology has become part of our daily lives,” Savin said.

Savin and the rest of the team are interested in understanding how their technology will impact existing applications and discover what new applications will be possible with increased sensitivity.

The study was published in the journal on January 1, 2025 Light: Science and Applications.