Journal
ACS NANO
Volume 14, Issue 4, Pages 4567-4576Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.0c00103
Keywords
HgTe; narrow band gap nanocrystals; infrared detection; gate-induced diode; graphene
Categories
Funding
- ERC [756225]
- Region Ile-de-France
- ANR [ANR11-IDEX-0004-02]
- Grant IPER-nano2, Copin, Frontal, Graskop
- Agence Innovation Defense
- Institut Universitaire de France
- Agence Nationale de la Recherche within the Investissement d'Avenir program [Labex NIE 11-LABX-0058_NIE, ANR-10-IDEX-0002-02]
- Agence Nationale de la Recherche under ANR MIXES [ANR-19-CE09-0028]
- ANR H2DH
- European Research Council (ERC) [756225] Funding Source: European Research Council (ERC)
- Agence Nationale de la Recherche (ANR) [ANR-19-CE09-0028] Funding Source: Agence Nationale de la Recherche (ANR)
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Nanocrystals are promising building blocks for the development of low-cost infrared optoelectronics. Gating a nanocrystal film in a phototransistor geometry is commonly proposed as a strategy to tune the signal-to-noise ratio by carefully controlling the carrier density within the semiconductor. However, the performance improvement has so far been quite marginal. With metallic electrodes, the gate dependence of the photocurrent follows the gate-induced change of the dark current. Graphene presents key advantages: (i) infrared transparency that allows back-side illumination, (ii) vertical electric field transparency, and (iii) carrier selectivity under gate bias. Here, we investigate a configuration of 2D/0D infrared photodetectors taking advantage of a high capacitance ionic glass gate, large-scale graphene electrodes, and a HgTe nanocrystals layer of high carrier mobility. The introduction of graphene electrodes combined with ionic glass enables one to reconfigure selectively the HgTe nanocrystals and the graphene electrodes between electron-doped (n) and hole-doped (p) states. We unveil that this functionality enables the design a 2D/0D p-n junction that expands throughout the device, with a built-in electric field that assists charge dissociation. We demonstrate that, in this specific configuration, the signal-to-noise ratio for infrared photodetection can be enhanced by 2 orders of magnitude, and that photovoltaic operation can be achieved. The detectivity now reaches 10(9) Jones, whereas the device only absorbs 8% of the incident light. Additionally, the time response of the device is fast (<10 mu s), which strongly contrasts with the slow response commonly observed for 2D/0D mixed-dimensional heterostructures, where larger photoconduction gains come at the cost of slower response.
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