Short Wave Infrared Devices Based on HgTe Nanocrystals with Air Stable Performances
Résumé
Colloidal quantum dots (CQDs) are candidates of interest for the design of low cost IR detector especially in the short wave infrared (SWIR; 0.8-3 µm), where the vicinity of the visible range makes the high cost of available technologies even more striking. HgTe nanocrystals are among the most promising candidates to address SWIR since their spectrum can be tuned all over this range while demonstrating photoconductive properties. However, several main issues have been kept under the rug, which prevents further development of active materials and devices. Here we address two central questions, which are (i) the stability of the device under ambient air condition and (ii) the reduction of dark current. Encapsulation of HgTe CQDs is difficult because of their extreme sensitivity to annealing, we nevertheless demonstrate an efficient encapsulation method based on a combination of O2 and H2O repellant layers leading to stability over >100 days. Finally, we demonstrate that the dark current reduction can be obtained by switching from a photoconductive geometry to a photovoltaic (PV) device, which is fabricated using solution and low temperature based approach. We demonstrate fast photoresponse (>10 kHz) and detectivity enhancement by 1 order of magnitude in the PV configuration at room temperature. These results pave the way for narrow bandgap CQD based cost-effective optoelectronic devices in developing next generation SWIR photonic systems.
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