Infrared photoconduction at the diffusion length limit in HgTe nanocrystal arrays

Narrow band gap nanocrystals offer an interesting platform for alternative design of low-cost infrared sensors. It has been demonstrated that transport in HgTe nanocrystal arrays occurs between strongly-coupled islands of nanocrystals in which charges are partly delocalized. This, combined with the scaling of the noise with the active volume of the film, make case for device size reduction. Here, with two steps of optical lithography we design a nanotrench which effective channel length corresponds to 5-10 nanocrystals, matching the carrier diffusion length. We demonstrate responsivity as high as 1kAW(-1), which is 10(5) times higher than for conventional mu m-scale channel length. In this work the associated specific detectivity exceeds 10(12) Jones for 2.5 mu m peak detection under 1V at 200K and 1kHz, while the time response is as short as 20 mu s, making this performance the highest reported for HgTe NC-based extended short-wave infrared detection. Infrared nanocrystals have become an enabling building block for the design of low-cost infrared sensors. Here, Chu et al. design a nanotrench device geometry at the diffusion length limit in HgTe nanocrystals and demonstrate the record high sensing performance operated in the short-wave infrared.