Skip to main content
eScholarship
Open Access Publications from the University of California

Ultrasensitive photodetectors exploiting electrostatic trapping and percolation transport

  • Author(s): Zhang, Y
  • Hellebusch, DJ
  • Bronstein, ND
  • Ko, C
  • Ogletree, DF
  • Salmeron, M
  • Alivisatos, AP
  • et al.
Abstract

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.

Main Content
Current View