Nanoscale miniaturization of semiconductor devices has led to major advances in opto/nanoelectronics. However, this device downscaling also brought technological issues. Among them, one of the most detrimental is the self-heating effect due to the thermalization of hot carriers generated by high electric fields. This self-heating effect results in significant reduction in performance and lifetimes of the devices. On the other hand, the refrigeration of the entire systems is extremely power consuming. The development of efficient cooling is then one of the major scientific and environmental issues.
The aim of the PhD thesis is then to conceive, based on quantum transport simulations, a new generation of cooling nano-devices. The student will focus on multibarrier semiconductor heterostructures since we recently demonstrated that an asymmetric double barrier GaAs-AlGaAs device (Fig.1-a)) can act on the electronic and phononic bath’s refrigeration [1-3]. In this structure, “cold” electrons are injected into the quantum well (QW) via a resonant tunneling effect through a thin potential barrier. “Hot” electrons are extracted from the QW through a thermionic process above the thick AlGaAs alloy. As a result, the lattice of the QW cools and the one of the right region heats. We have shown that such a low-energy-injection/high-energy-extraction device can induce an electron cooling thanks to an evaporative effect  (See Fig.1-b)). In particular, Fig.1-c) shows the electron temperature in the QW is reduced from room temperature by as much as 50 K.
The PhD student will develop and use an “in-house” quantum transport atomistic code based on the non-equilibrium Green’s Function (NEGF) formalism. We implemented a numerically efficient method to treat electron-phonon and phonon-phonon interactions , which led to a NEGF quantum simulations able to calculate all the physical properties of the system, including the temperature profiles of both electrons and phonons.
Collaboration with the LIMMS-University of Tokyo, ENS-Paris, IPVF-Saclay:
This PhD grant is part of the ANR GELATO project which involves four partners: IM2NP, LIMMS-UTokyo, LPENS and IPVF.
The PhD student will be enrolled at the Aix-Marseille University in the Nanodevice Quantum Simulation group of the IM2NP laboratory (www.im2np.fr). He/she will be in charge of the theoretical/simulation part of the project and will benefit from cutting edge computational facilities with a local cluster of more than 600 cores. Moreover, he/she will be in close interactions with the members of Prof. Hirakawa’s group at the LIMMS-UTokyo (https://thz.iis.u-tokyo.ac.jp/en/), in charge of the experimental part. Biannual travels between France and Japan will be also scheduled to strengthen the interactions.
Eligibility criteria of the applicants:
Applicants must hold a master degree in physics, material science or electrical engineering. Experience in programming would be appreciated.
For more information, please contact:
Dr. Marc Bescond
IM2NP UMR-CNRS 7334 at the Aix-Marseille University.
- M. Bescond, D. Logoteta, F. Michelini, N. Cavassilas, T. Yan, A. Yangui, M. Lannoo, H. Hirakawa, “Thermionic cooling devices based on resonant-tunneling AlGaAs/GaAs heterostructure,” J. Phys.: Condens. Matter, 30, 064005 (2018).
- A. Yangui, M. Bescond, T. Yan, N. Nagai, and K. Hirakawa, “Evaporative electron cooling in asymmetric double barrier semiconductor heterostructures,” Nature Commun. 10, 4504 (2019).
- M. Bescond and K. Hirakawa, “High performance thermionic cooling devices based on tilted-barrier semiconductor heterostructures”, Phys. Rev. Appl., 14, 064022 (2020).
- Y. Guo, M. Bescond, Z. Zhang, M. Luisier, M. Nomura, and S. Volz, “Quantum mechanical modeling of anharmonic phonon-phonon scattering in nanostructures”, Phys. Rev. B, 102, 195412 (2020).
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