Using Activated Transport in Parallel Nanowires for Energy Harvesting and Hot Spot Cooling

TL;DR

This paper investigates the thermoelectric properties of doped semiconductor nanowire arrays, revealing how their energy harvesting and cooling capabilities depend on impurity band positioning and local heat exchange mechanisms.

Contribution

It introduces a detailed analysis of thermopower, conductance, and heat exchange in nanowire arrays using a resistor network model, highlighting potential for energy harvesting and hot spot cooling.

Findings

Large power factors near band edges due to high thermopower.

Heat exchange occurs mainly at electrodes, enabling localized cooling.

Conductance scales with the number of nanowires, enhancing power output.

Abstract

We study arrays of parallel doped semiconductor nanowires in a temperature range where the electrons propagate through the nanowires by phonon assisted hops between localized states. By solving the Random Resistor Network problem, we compute the thermopower $S$, the electrical conductance $G$, and the electronic thermal conductance $K^e$ of the device. We investigate how those quantities depend on the position -- which can be tuned with a back gate -- of the nanowire impurity band with respect to the equilibrium electrochemical potential. We show that large power factors can be reached near the band edges, when $S$ self-averages to large values while $G$ is small but scales with the number of wires. Calculating the amount of heat exchanged locally between the electrons inside the nanowires and the phonons of the environment, we show that phonons are mainly absorbed near one electrode and emitted near the other when a charge current is driven through the nanowires near their band edges. This phenomenon could be exploited for a field control of the heat exchange between the phonons and the electrons at submicron scales in electronic circuits. It could be also used for cooling hot spots.