MoS2 -HgTe Quantum Dot Hybrid Photodetectors beyond 2 µm.

Mercury telluride (HgTe) colloidal quantum dots (CQDs) have been developed as promising materials for the short and mid-wave infrared photodetection applications because of their low cost, solution processing, and size tunable absorption in the short wave and mid-infrared spectrum. However, the low mobility and poor photogain have limited the responsivity of HgTe CQD-based photodetectors to only tens of mA W-1 . Here, HgTe CQDs are integrated on a TiO2 encapsulated MoS2 transistor channel to form hybrid phototransistors with high responsivity of ≈106 A W-1 , the highest reported to date for HgTe QDs. By operating the phototransistor in the depletion regime enabled by the gate modulated current of MoS2 , the noise current is significantly suppressed, leading to an experimentally measured specific detectivity D* of ≈1012 Jones at a wavelength of 2 µm. This work demonstrates for the first time the potential of the hybrid 2D/QD detector technology in reaching out to wavelengths beyond 2 µm with compelling sensitivity.