IR Tech Breakthrough Offers Biometric, Computer Vision Applications

The Belgian tech firm IMEC has developed a pinned diode structure for thin-film sensors that allows for cost-effective imaging of infrared light. The company says it offers applications in areas such as IR cameras in autonomous vehicle and face-scanning smartphone cameras.

IMEC’s innovative approach involves enhancing the functionality of thin-film-based image sensors by incorporating a specialized structure known as a pinned photodiode (PPD) within the readout circuit. This advancement entails combining two distinct components: a short-wavelength infrared (SWIR) quantum-dot photodetector and an indium-gallium-zinc oxide (IGZO) thin-film transistor.

A short-wavelength infrared (SWIR) quantum-dot photodetector is a specialized component used in imaging technology to detect and capture light in the short-wavelength infrared spectrum. The SWIR spectrum encompasses wavelengths that are slightly longer than those visible to the human eye, making it a crucial range for various applications, including night vision, remote sensing, and medical imaging.

Quantum dots, on the other hand, are nanoscale semiconductor particles with unique optical properties. When incorporated into photodetectors, quantum dots can absorb light and convert it into electrical signals. Quantum-dot photodetectors have the advantage of being highly sensitive to specific wavelengths of light, allowing for more accurate detection and improved imaging capabilities.

An indium-gallium-zinc oxide (IGZO) thin-film transistor, meanwile, is a type of semiconductor device used to control the flow of electrical current in electronic circuits. It is composed of a thin layer of a compound semiconductor material called IGZO, which is a combination of indium, gallium, and zinc oxides. IGZO thin-film transistors are commonly used in various display technologies, such as liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), and touchscreens. IGZO thin-film transistors are known for their low power consumption, high transparency, and flexibility.

These elements are integrated to form a PPD pixel. The resultant array is then seamlessly integrated into a thin-film SWIR image sensor using a complementary metal-oxide-semiconductor (CMOS) readout circuit.

What makes this achievement remarkable is the substantial reduction in the read-out noise to 6.1e- (a tiny electronic unit) compared to the significantly higher noise level of over 1000e- in a conventional 3T sensor. This noise reduction marks a substantial leap in performance.

Project lead Nikolas Papadopoulous says the first-of-its-kind prototype enables infrared images to be captured “with less noise, distortion or interference, and more accuracy and detail.”

His team’s project has been detailed in the August 2023 issue of Nature Electronics, in a paper title “Pinned photodiode for monolithic thin-film image sensors”.

Source: Printed Electronics

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August 25, 2023 – by the FindBiometrics Editorial Team