Cooling devices based on non-equilibrium transport in semiconductor heterostructures – GELATO

GELATO aims at designing disruptive highly efficient thermionic cooling nano-devices. It is motivated by the urgent technological need to control joule heating in nanoelectronics in a context of energy shortage. So far, most of the studies on solid-state cooling are based on the classical thermoelectric Peltier effect. In the thermoelectric cooling, electrons propagate diffusively through the materials, generating Joule heating, and leading to the reduction of the efficiency. GELATO then adopt a paradigm shift: we focus on nanoscaled cooling devices in which transport of electrons and heat becomes strongly ballistic, and whose working principle applies far from equilibrium. This is the field of thermionic cooling. We will focus on multi-barrier heterostructures since members of the consortium recently demonstrated that such device can efficiently acts on refrigeration at the nanoscale. Two scientific tasks will be addressed. The first one will investigate the electron and lattice temperature in double-barrier asymmetric heterostructure. We will investigate the interplay between lattice and electron refrigeration in non-equilibrium systems. We will reach a clear understanding by operating a comprehensive optimization procedure (modifying materials, geometries and temperature) thanks to numerical simulation guidance. It will lead to the determination of general physical parameters providing the highest temperature reduction. The second task will be dedicated to the conception of more sophisticated refrigeration devices. We will investigate three structures, each of them assessing a specific physical cooling effect:
i) “quantum cascade cooler (QCC)”
A superlattice heterostructure can drastically improve the cooling power. By monitoring the thickness of each layer in order to progressively increase the energy of the QW states, a transmitted single electron can absorb several phonons, leading to the refrigeration of the entire structure. This device is then identified as “quantum cascade cooler”.
ii) hybrid (metal-semiconductor) structure
Since the strategy to cool the lattice is to maximize heat pumping in the QW, it is desirable to increase the electronic heat capacity of this region. We will then consider a hybrid strategy by using a metal (or a highly doped semi-conductor) in the QW and will conserve the AlGaAs elsewhere.
iii) opto-thermionic pumping
In the opto-thermionic device, hot electrons entering the collector will recombine by emitting photons and will thus evacuate the heat out of the device.
This work will then pave the way to a new era of research in thermoelectricity and will lead towards the fabrication of nanodevices providing unprecedented cooling efficiency.