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INFRARED DETECTION with QUANTUM DOTS
Infrared radiation, which is emitted by all objects with a temperature above 0 K, carries valuable information about temperature, composition, and structure of objects and environments. As a consequence, infrared detection finds wide-ranging applications in fields such as thermal imaging, night vision, remote sensing and environmental monitoring. The ability to accurately detect and measure infrared radiation is crucial for the scientific and technological advancement in these fields and requires the development of the so-called 'third-generation' detectors [1]. One of the most interesting solutions which is being investigated is based on intraband transition in Quantum Dots (QDs). The detection mechanism based on these transitions, which occur between QD states in the condution band, is schematized in the top panel of the Figure. When an electron filling the ground state absorbs a photon, it is excited to a high-energy quantum state,from where it is extracted through thermionic or tunneling processes and it is finally collected at the contacts. Since the position of the quantum states depends on the geometry of the QDs, the absorption wavelength can be tuned and optimized for each specific application. The bottom panel of the Figure shows a typical QD-IR photodetector device and a view of the QDs composing the active layer.
Figure:
Top Panel: Band diagram of a QD infrared photodetector where all the significant processes are indicated.
Bottom Panel: Structure of a QD-based IR photodetector. The inset show the morphology of the QDs
References
[1] A. Rogalski, J. Antoszewski and L. Faraone, Third-generation infrared photodetector arrays, J. Appl. Phys. 105, 091101 (2009).
OUR APPROACH
Engineering the geometrical parameters of QDs is fundamental to have a precise tuning of the absorption window and an optimized absorption process. Droplet Epitaxy (DE) is the most advanced technique in this regard as it allows for an advanced engineering of QD states, which grants us the ability to control independently the position of the QDs ground state and the spacing between energy levels. As a consequence, the peculiar properties of DE allow to control not only the transition energy but also the capture and extraction dynamics of electrons.
Following this route, we are aiming at the realization of an QD-based infrared detector working at room temperature with a fast response and a narrow absorption linewidth.
Relevant Publications:
S. Vichi et al. Droplet epitaxy quantum dot based infrared photodetectors. Nanotechnology 31, 245203 (2020) DOI: https://doi.org/10.1088/1361-6528/ab7aa6
S. Vichi et al. Optically controlled dual band quantum dot infrared photodetector, Nanomaterials and Nanotechnology 12, (2022) DOI: https://doi.org/10.1177/18479804221085790
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