Colloidal nanocrystals are attracting an increasing interest since their recent introduction as light emitters for the last generation of displays. Their role in optoelectronics is expected to further develop, as several companies are diversifying the use of these nanoparticles for applications in other markets than displays, like night-vision for security, surveillance and driving assistance. In this respect nanocrystals are very promising for low cost photodetectors in the mid-infrared (mid-IR) wavelength range, where current technologies remain expensive being driven by epitaxially grown III-V and II-VI semiconductors.
In this project we aim at realizing mid-IR detectors based on colloidal nanocrystals with performances that at the end of the project will be comparable to the state-of-the-art of current technologies. Two types of nanoparticles will be used: HgTe for 2.5-5µm wavelength range, exploiting interband transitions; HgSe for 8-10µm range, exploiting intraband transitions. The key limitation of state-of-the-art nanocrystal based detectors is their small carrier diffusion length (50-100nm) compared to the absorption depth (few µm) that hinders the majority of the photoexcited carriers to reach to the contacts. Our strategy to beat present detector limitations will be to work in parallel on i) the material side, ii) the control of light-matter interaction and iii) the optimization of the detector architecture. In particular we will take advantage of recent developments on refined synthesis for higher carrier mobility, plasmon based architectures and coupling into microcavities to enhance the electromagnetic field in a small effective volume.
This approach is ideally suited for the scientific competences present in the consortium. LPENS is a leader in the domain of infrared quantum optoelectronics; furthermore they recently demonstrated a quantum well infrared photodetector with a signal to noise ratio greatly enhanced by the use of a plasmonic microcavity. INSP has pioneered the realization of nanocrystal based IR photodetectors. IPCMS has a strong experience in nanocrystal based sensors and ONERA is a leader in IR detection and plasmonic devices.
The project will be organized in three main workpackages (WP). The first WP is devoted to the synthesis and characterization of the nanocrystals, and to the determination of their electronic spectrum. In the second WP we will study charge transport and light-matter interaction in plasmonic resonators. Finally, in WP3 we will realize and characterize IR photodetectors with three different architectures. For the realization of our devices, we propose a disruptive approach, hybridizing device architectures developed for III-V optoelectronics and clean-room processing typical of microelectronics with the synthesis of colloidal nanocrystals. As a consequence, an important part of the proposed work will be to adapt the fabrication process of plasmonic microcavities and resonators to the specificities of the material system that will be used. This approach requires a strong interaction between all the partners of the consortium.
The possibility of realizing plasmonic resonators embedding nanocrystal films and well suited for charge transport will also offer us the opportunity to address fundamental issues well beyond the scope of photodetection. Indeed, we will study the interplay between light-matter coupling and charge transport in a material system where hopping is the dominant transport mechanism. Indeed, several theoretical and experimental studies have shown that charge transport can be profoundly modified and enhanced by the presence of a strong interaction with a cavity mode. In this project this fascinating phenomenon will be studied with different resonator architectures, and in different transport regimes with unipolar or bipolar devices.
Madame Angela Vasanelli (Laboratoire de physique de l'ENS)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
INSP Institut des nanosciences de Paris
IPCMS Institut de physique et chimie des matériaux de Strasbourg (UMR 7504)
ONERA Office National d'Etudes et de Recherches Aérospatiales
LPENS Laboratoire de physique de l'ENS
Help of the ANR 536,055 euros
Beginning and duration of the scientific project: March 2020 - 42 Months