Nanocrystals are promising materials for the design of low-cost, infrared (IR) detectors. Here we focus on HgTe colloidal quantum dots (CQDs) as an active material for detection in the extended… Click to show full abstract
Nanocrystals are promising materials for the design of low-cost, infrared (IR) detectors. Here we focus on HgTe colloidal quantum dots (CQDs) as an active material for detection in the extended short-wave infrared (2.5 μm as cutoff wavelength). In this paper, we propose a strategy to enhance the performances of previously reported photodiodes. In particular, we integrate in this diode a unipolar barrier, whose role is to reduce the dark current injection and subsequently enhance the signal-to-noise ratio. We demonstrate that such unipolar barrier can be designed from another layer of HgTe CQDs with a wider band gap. Using a combination of IR spectroscopy and photoemission, we show that the barrier is resonant with the absorbing layer valence band, while presenting a clear offset with the conduction band. The combination of contacts with improved design and use of a unipolar barrier allows us to reach a detectivity as high as 3 × 108 Jones at room temperature with 3 dB cut off frequency above 10 kHz.
               
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