This talk will discuss surface gating of the carrier density in colloidal quantum dots and the applications for infrared detection and emission. Doping of carriers in colloidal quantum dots (CQD) is important for a number of applications. While doping in bulk semiconductors is achieved with heterovalent impurities, CQDs can be doped by charge transfer from outside using reducing reagents or electrochemistry. In addition, the positions of the energy levels inside the particle and the outside Fermi level depend on the polarity of the interface, such that the surface composition can affect doping. This is the concept of surface gating. A striking demonstration is the filling and emptying of the quantum states of HgSe and HgS quantum dots by enrichment of the surface in metal or sulfur atoms. These are the first CQDs to exhibit carrier doping in ambient conditions. CQDs for infrared photodetection or emission is now extended to wider gap systems by using the intraband transitions of the doped quantum dots, first investigated nearly two decades ago.
Philippe Guyot-Sionnest, "Surface gating of colloidal semiconductor quantum dots to optimize mid-infrared detection and emission (Conference Presentation)," Proc. SPIE 9923, Physical Chemistry of Interfaces and Nanomaterials XV, 99230U (Presented at SPIE Nanoscience + Engineering: August 30, 2016; Published: 11 November 2016); https://doi.org/10.1117/12.2236219.5161498049001.
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