Infrared Imaging using thermally stable HgTe/CdS nanocrystals

TL;DR

This paper presents thermally stable HgTe/CdS nanocrystals for infrared imaging, demonstrating improved thermal stability, reduced dark current, and enhanced photoconductive gain suitable for practical infrared sensing applications.

Contribution

The study introduces CdS shells on HgTe nanocrystals, enhancing thermal stability and photoconductive properties, advancing infrared sensor technology.

Findings

CdS shells prevent redshift upon annealing

Enhanced photoconductive gain observed

Material exhibits p-type behavior after shelling

Abstract

Transferring the nanocrystals (NCs) from the laboratory environment toward practical applications has raised new challenges. In the case of NCs for display and lightning, the focus was on reduced Auger recombination and maintaining luminescence at high temperatures. When it comes to infrared sensing, narrow band gap materials are required and HgTe appears as the most spectrally tunable platform. Its low-temperature synthesis reduces the growth energy cost yet also favors sintering. As a result, once coupled to a read-out circuit, the Joule effect aggregates the particles leading to a poorly defined optical edge and dramatically large dark current. Here, we demonstrate that CdS shells bring the expected thermal stability (no redshift upon annealing, reduced tendency to form amalgams and preservation of photoconduction after an atomic layer deposition process). The peculiar electronic structure of these confined particles is unveiled using k.p self-consistent simulations showing a significant exciton biding energy at around 200 meV. After shelling, the material displays a p-type behavior that favors the generation of photoconductive gain. The latter is then used to increase the external quantum