In this paper, we discuss recent progress obtained on infrared nanocrystal based on mercury chalcogenides (HgTe and HgSe). These materials can become some key building blocks for the next generation of infrared optoelectronic devices. To reach this goal, the infrared nanocrystals need to combine fine control on the optical features and efficient electronic transport. Here, we report about (i) the development of HgTe NPL for enhanced optical features (narrower and faster PL) in the near IR and (ii) about the development of self-doped nanocrystals of HgSe to demonstrate tunable intraband absorption up to the THz range.
In this article we discuss the infrared properties of self-doped nanocrystals and in particular the case of HgSe. HgSe colloidal quantum dots have recently been reported for their tunable optical features all over the mid infrared from 3 to 20 μm. Their optical absorption is a combination of interband absorption at high energy and intraband absorption at low energy. The latter results from the self-doped character of HgSe. The origin of this self-doping is also discussed. We demonstrated that the doping results from the combination of the narrow band gap and high work function of HgSe, which leads to a reduction of the CQD by the water in the environment. In addition, we demonstrated that the doping density can be tuned over an order of magnitude thanks to the control of the capping ligands.
The transport and thermal properties of HgTe colloidal quantum dot films with cut-off
wavelengths in the mid-IR are investigated. The cut-off wavelength of this material can be tuned
over the 3-5 μm range, which makes it a promising alternative to existing high cost detectors. Post
deposition processes such as ligand exchange and atomic layer deposition are investigated as a way
to increase the carrier mobility.