HgTe Nanocrystals for SWIR Detection and Their Integration up to the Focal Plane Array

Abstract

Infrared applications remain too often a niche market due to their prohibitive cost. Nanocrystals offer an interesting alternative to reach cost disruption especially in the shortwave infrared (SWIR, λ<1.7 µm) where material maturity is now high. Two families of materials are candidate for SWIR photoconduction: lead and mercury chalcogenides. Lead sulfide typically benefits from all the development made for wider bap gap such as the one made for solar cells, while HgTe takes advantage of development relative to mid wave infrared detector. Here we make a fair comparison of the two material detection properties in the SWIR and discuss the material stability. At such wavelengths, studies have been mostly focused on PbS rather than on HgTe, therefore we focus in the last part of the discussion on the effect of surface chemistry on the electronic spectrum of HgTe nanocrystals. We unveil that tuning the capping ligands is a viable strategy to adjust the material from p-type to ambipolar. Finally, HgTe nanocrystals are integrated into multi pixel devices to quantize spatial homogeneity and onto read out circuits to obtain fast and sensitive infrared laser beam profile.

Near Unity Absorption in Nanocrystal Based Short Wave Infrared Photodetectors Using Guided Mode Resonators

“…Compared to the work done on non-colloidal semiconductors, the main challenge is to design a structure which accounts for the fragility of the colloidal materials. PbS nanocrystals can easily be oxidized, while HgTe nanocrystals sinter upon annealing even at relatively low temperatures 53 . Our approach is to design a structure in which all lithography steps are conducted before the CQD deposition, see Figure S3 for fabrication details.…”

The Strong Confinement Regime in HgTe Two-Dimensional Nanoplatelets

“…This lack appears to be detrimental since device progresses appear to be strongly correlated to a deeper understanding of the material and its electronic structure. For the sake of illustration, systematic measurements of the band alignment 28,10,29 in HgTe NCs have enabled the design of unipolar barriers 29…”

“…Over the past decade, infrared optoelectronics 2 have also generated interest with applications such as solar cells 3,4 and low-cost infrared (IR) sensors 5,6,7,8,9 including focal plane arrays. 10,11,12 For these IR applications, narrow band gap materials such as lead and mercury chalcogenides are used, and the relative change of the band gap resulting from confinement can be even more important. Thus, the lowest energy optical feature of HgTe can be tuned from the THz 13,14 to the visible range (i.e.…”

Electroluminescence from HgTe Nanocrystals and Its Use for Active Imaging

“…Our finding paves the way for an all nanocrystal based active imaging setup by combining the proposed LED with the recent demonstration of HgTe nanocrystal based SWIR focal plane array. 45…”