High-Performance Thermionic Cooling Devices Based on Tilted-Barrier Semiconductor Heterostructures

Abstract

We study by means of full quantum simulations an asymmetric double-barrier semiconductor heterostructure refrigerator combining resonant tunneling filtering and thermionic emission. By varying the quantum well thickness, we first investigate the influence of the activation energy W on the coefficient of performance (COP) and cooling power. We show that the best performances are obtained when W equals the polar optical phonon energy of the material. However we also emphasize that cooling power and COP are severely limited by tunneling current at high bias. We then propose an original structure with a tilted potential barrier to reduce this degrading effect. Quantum simulations demonstrate that cooling properties of such tilted barrier device are significantly improved in out-of-equilibrium regime, where the thermionic cooling concept offers its best efficiency.

Temperature-Induced Revolving Effect of Electronic Flow in Asymmetric Double-Barrier Semiconductor Heterostructures

“…In order to theoretically study such a quantum device, we couple both electron and phonon transport. The approach being already described in previous studies 4,5,9 , we therefore briefly remind below the milestones of the theory and the computational implementation.…”

“…As a comparison, Figure 4 shows the electron current spectrum in the same device when a 0.1 V bias is applied without any temperature gradient (T Emit =T Coll =300 K). In that configuration, the device operates like a cooling structure 5,8 . As expected, we see that the electron flow goes from the emitter region towards the collector side for all the energies, following the Femi levels difference between the two reservoirs.…”

“…In order to capture the key aspects of the physics, we use the quantum non-equilibrium Green's function (NEGF) method. Our quantum transport code takes into account the thermal effects by self-consistently coupling the electron transport equations expressed within the NEGF formalism with the heat equation 4,5 . We also use the virtual probe concept to calculate the electron temperature and electrochemical potential inside the device 6,7 .…”

Comprehensive Analysis of Electron Evaporative Cooling in Double-Barrier Semiconductor Heterostructures

“…In order to capture the key aspects of the physics, we use the quantum non-equilibrium Green's function (NEGF) method. Our quantum transport code takes into account the thermal effects by selfconsistently coupling the electron transport equations expressed within the NEGF formalism with the heat equation 24,25 . We also use the virtual probe concept to calculate the electron temperature and electrochemical potential inside the device 26,27 .…”

Electron Transport in Double-Barrier Semiconductor Heterostructures for Thermionic Cooling

“…Indeed, we recently demonstrated that (Al, Ga)As/GaAs asymmetric double-barrier thermionic cooling structures could reduce the electron temperature, T e , from 300 K down to 250 K by applying a bias voltage to the structure [19,20]. In the asymmetric double-barrier thermionic cooling structures, the two-step sequential current that is carried by resonant injection into the QW and subsequent thermionic emission plays an essential role [21]. To improve the cooling performance, an understanding of electron transport and optimization of structural parameters are needed.…”