HgTe colloidal quantum dot photodetectors show promise as an inexpensive, solution processed, alternative to conventional, epitaxially grown, single crystal infrared detectors. Recent work on the thermodynamic limits of these materials suggests that their low Auger recombination rate may allow for better performance than that of conventional detectors in the mid-infrared. Although previous work showed that mid-IR HgTe quantum dot detectors are background limited at cryogenic temperatures, they also showed that there is a ~20-fold decrease in the quantum efficiency from 150K to 300K. The focus of this work is to raise the operation temperature so that thermal imaging can be done at or close to room temperature.<br/>We will describe the modified synthesis of the dots that produces materials with higher electrical mobility, and how this increases the diffusion length and collection efficiency. We will describe modifications of the p and n-doping methods and how these lead to higher shunt resistance diodes. Microfabrication will be shown to enhance the optical absorption of the diodes. The modelling of the IV curves helps to better understand the mechanisms limiting performance. The temperature dependence, the origin of shunt (recombination mechanisms) and series resistance (electrodes) are rather well understood with a simple model. As a result of this work, the single element detectors allow thermal imaging at higher temperature than previously reported and closer to the thermodynamic limit determined by the non-radiative recombination of the materials.

Mid-infrared photodiodes based on HgTe quantum dot inks

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ACS Fall 2022

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