Selective energy filtering in a multiple-quantum-well nanodevice: The quantum cascade cooler

Using quantum transport simulations, we study the operating principle of a proposed quantum cascade cooler, a multiple-quantum-well structure whose cooling capabilities rely on combined resonant tunneling and thermionic-emission filtering. We couple charge and heat transport by self-consistently solving nonequilibrium Green's functions and the heat equation, and we subsequently calculate the thermodynamic properties of the electrons using noninvasive virtual probes. We show that this device exhibits bias-dependent electron-temperature oscillations emerging from electron-phonon interactions and intersubband transitions. Finally, we show the advantages of a multiple-quantum-well structure over a single quantum well and discuss the actual potential for such a structure to effectively cool down the crystal lattice upon optimization.