New photodetector is a shining light

Australian engineers appear to have raised the bar for photodetector technology, developing a device that is incredibly thin but able to see all shades of light.

Writing in the journal Advanced Materials, researchers from RMIT University, led by Vaishnavi Krishnamurthi, suggest their successful prototype provides new opportunities to integrate electrical and optical components on the same chip.

Photodetectors, or photosensors, work by converting information carried by light into an electrical signal, and are used in everything from gaming consoles to fibre optic communication.

However, they currently are unable to sense more than one colour in the one device, Krishnamurthi says, which means they have remained bigger and slower than other technologies, such as the silicon chip, with which they integrate.

The RMIT prototype can interpret light ranging from deep ultraviolet to near infrared wavelengths, making it sensitive to a broader spectrum than a human eye. And it is less than a nanometre thick.

Success came from taking a completely different approach.

Current photodetector technology relies on a stacked structure of three to four layers, but the RMIT team worked out how to use a nanothin layer –a single atom thick – on a chip.

The material used, tin monosulfide, also is low-cost and naturally abundant, making it attractive for electronics and optoelectronics, says co-author and chief investigator Sumeet Walia.

“The material allows the device to be extremely sensitive in low-lighting conditions, making it suitable for low-light photography across a wide light spectrum,” he says.

A major challenge was ensuring electronic and optical properties didn’t deteriorate when the photodetector was shrunk – a technological bottleneck that, the researchers say, had previously prevented miniaturisation of light detection technologies.

Walia says the team is now looking at industry applications for the photodetector, which can be integrated with existing technologies such as CMOS chips.

“With further development, we could be looking at applications including more effective motion detection in security cameras at night and faster, more efficient data storage,” he says.

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