Power and efficiency analysis of a realistic resonant tunneling diode thermoelectric

Low-dimensional systems with sharp features in the density of states have been proposed as a means to improving the efficiency of thermoelectric devices. Quantum dot systems, which offer the sharpest density of states achievable, however, suffer from low power outputs while bulk (3-D) thermoelectrics, while displaying high power outputs, offer very low efficiencies. Here, we analyze the use of a resonant tunneling diode structure that combines the best of both aspects, that is, density of states distortion with a finite bandwidth due to confinement that aids the efficiency and a large number of current carrying transverse modes that enhances the total power output. We show that this device can achieve a high power output ($\sim 0.3$ MW$/m^2$) at efficiencies of $\sim 40\%$ of the Carnot efficiency due to the contribution from these transverse momentum states at a finite bandwidth of $kT/2$. We then provide a detailed analysis of the physics of charge and heat transport with insights on parasitic currents that reduce the efficiency. Finally, a comparison between the resonant tunneling diode and a quantum dot device with comparable bandwidth reveals that a similar performance requires ultra-dense areal quantum dot densities of $\sim 10^{12}/cm^2$.