APPLICATIONS OF TECHNOLOGY:
- Visible light cameras – CCD and CMOS technologies
- Night vision cameras
- X-ray / Gamma ray detectors
- Ultraviolet flame / smoke detectors
- Cherenkov particle detection
- High photosensitivity – low-noise electron transport with high mobility
- Scalable fabrication process
- Long carrier lifetime
- Easily integrated into microelectronics
A group of Berkeley Lab researchers led by Paul Alivisatos and Miquel Salmeron have engineered photodetectors with unprecedented photosensitivity by sequestering the majority and minority carriers in different local domains. In this way, minority carrier trapping and majority carrier transport can be independently tuned to achieve, simultaneously, high photocarrier quantum yield, long carrier lifetime, low noise electron transport with high mobility, and tunable hole detrapping time. The solution-processable fabrication process used is scalable and eliminates the need for selective doping.
The researchers produced the first pre-designed nanocrystal structures, which physically separate hole and electron charge carriers to achieve a specific detectivity of approximately 5×1017, the highest ever reached by any visible/infrared detector at room temperature. These structures have a photoconductive gain of up to approximately1010 electron per photon in the visible range. The device is also sensitive to light in the wavelength range 350-850 nanometers (nm), and can function as quickly as one microsecond.
Photodetectors are widely used in digital imaging, optical communications, remote sensing, nighttime surveillance, medical imaging, and other applications. Their sensitivity – the ability to differentiate signal from noise – is key for high fidelity photon detection and imaging, especially when signals are weak. Other methods of achieving a high photoconductive gain have been less successful. Photomultipliers and avalanche photodiode devices require high bias, yield excess noise, and can be difficult to integrate into microelectronics. With photoconductors, minority trap carriers can be in the pathway of majority carrier transport, leading to limited photon sensitivity. With an easily scalable process and exceptional photosensitivity characteristics, the Berkeley Lab device promises to lead the next generation of high-sensitivity cameras and improve upon many other applications where detection of small photon flux is needed.
FOR MORE INFORMATION:
Zhang, Y., Hellebusch, D., Bronstein, N., Changhyun, K., Ogletree, F., Salmeron, M., Alivisatos, P. “Ultrasensitive photodetectors exploiting electrostatic trapping and percolation transport,” Nature Communications 7, June 21, 2016.
DEVELOPMENT STAGE: Proven principle.
STATUS: Issued U. S. Patent # 10,177,271. Available for licensing or collaborative research.
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