Lawrence Berkeley National Laboratory
Ultrasensitive photodetectors exploiting electrostatic trapping and percolation transport.
- Author(s): Zhang, Yingjie
- Hellebusch, Daniel J
- Bronstein, Noah D
- Ko, Changhyun
- Ogletree, D Frank
- Salmeron, Miquel
- Alivisatos, A Paul
- et al.
Published Web Locationhttps://doi.org/10.1038/ncomms11924
The sensitivity of semiconductor photodetectors is limited by photocarrier recombination during the carrier transport process. We developed a new photoactive material that reduces recombination by physically separating hole and electron charge carriers. This material has a specific detectivity (the ability to detect small signals) of 5 × 10(17) Jones, the highest reported in visible and infrared detectors at room temperature, and 4-5 orders of magnitude higher than that of commercial single-crystal silicon detectors. The material was fabricated by sintering chloride-capped CdTe nanocrystals into polycrystalline films, where Cl selectively segregates into grain boundaries acting as n-type dopants. Photogenerated electrons concentrate in and percolate along the grain boundaries-a network of energy valleys, while holes are confined in the grain interiors. This electrostatic field-assisted carrier separation and percolation mechanism enables an unprecedented photoconductive gain of 10(10) e(-) per photon, and allows for effective control of the device response speed by active carrier quenching.