Homogenous $In_{x}Ga_{1-x}N$ alloys on ZnO substrates: A new approach for high performance thermoelectric materials

TL;DR

This paper demonstrates that homogeneous InGaN alloys grown on ZnO substrates exhibit high thermoelectric efficiency with a record high zT of 0.86 at room temperature, surpassing traditional materials like SiGe.

Contribution

The study introduces a new method to produce high-quality homogeneous InGaN alloys with no phase separation at high Indium content for thermoelectric use.

Findings

Achieved a record high room temperature zT of 0.86.

Demonstrated large electrical conductivities from oxygen co-doping.

Observed low thermal conductivities due to alloy scattering.

Abstract

High performance thermoelectric materials for wide-range temperature applications still remains a challenge. In this study, we have produced high-quality homogeneous $In_{0.32}Ga_{0.68}N$ on ZnO substrates, with no phase separation at high Indium content, using metal organic chemical vapor deposition for thermoelectric applications. A record high room temperature figure of merit zT is obtained of 0.86, which is five times larger than that of SiGe, the current state of the art high temperature thermoelectric material. These materials are shown to have a nearly perfect doping concentration to maximize zT regardless of the scattering mechanism. This almost one order of magnitude increase in zT is due to large electrical conductivities from oxygen co-doping as well as low thermal conductivities from alloy scattering. The maximum power factor reached was $77.98x10^{-4} W/mK^{2}$ at 300K for $In_{0.32}Ga_{0.68}N$ alloys at a carrier concentration $~6.25x10^{20} cm^{-3}$. This work indicates that $In_{x}Ga_{1-x}N$ alloys have great potential for thermoelectric applications especially at a high temperature range.