Extracting Bulk-like Semiconductor Parameters from the Characterization of Colloidal Quantum Dot Film Photoconductors

A simple photoconductor structure based on a HgTe colloidal quantum dot (CQD) film on a field-effect transistor substrate is analyzed to provide quantitative information on the mobility, Fermi energy, and carrier number. Then, from the photocurrent with a calibrated light source and the optical constants of the materials, the carrier lifetime and recombination mechanism can be determined. The study confirms that geminate recombination is the dominant lifetime mechanism for these mid-infrared HgTe CQD films instead of trapping or Auger recombination. This work is a step toward answering the general question whether the individual properties of CQDs and their distribution in a film can be related to the simpler macroscopic optical and electrical properties of a homogeneous semiconductor.