Thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap semiconductors SiC, GaN, and ZnO

Zheng Huang,Jin-Cheng Zheng,Hui-Qiong Wang,Tie-Yu Lü

doi:10.1063/1.4931820

Zheng Huang, Jin-Cheng Zheng + Show 2 more

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https://doi.org/10.1063/1.4931820

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Journal: AIP Advances	Publication Date: Sep 1, 2015
Citations: 18	License type: CC BY 3.0

Affiliation: Institute of Theoretical Physics, Xiamen University

Abstract

We have investigated the thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap(n-type) semiconductors SiC, GaN, and ZnO based on first-principles calculations and Boltzmann transport theory. Our results show that the thermoelectric performance increases from 3C to 6H, 4H, and 2H structures with an increase of hexagonality for SiC. However, for GaN and ZnO, their power factors show a very weak dependence on the polytype. Detailed analysis of the thermoelectric properties with respect to temperature and carrier concentration of 4H-SiC, 2H-GaN, and 2H-ZnO shows that the figure of merit of these three compounds increases with temperature, indicating the promising potential applications of these thermoelectric materials at high temperature. The significant difference of the polytype-dependent thermoelectric properties among SiC, GaN, and ZnO might be related to the competition between covalency and ionicity in these semiconductors. Our calculations may provide a new way to enhance the thermoelectric properties of wide-band-gap semiconductors through atomic structure design, especially hexagonality design for SiC.

Highlights

Thermoelectric (TE) materials have attracted a lot of attention in recent years because of their ability to convert heat energy into electricity with reduced pollution.[1,2,3] The thermal–electricity conversion efficiency of TE materials is defined as the dimensionless figure of merit ZT = S2σT/κ, where T is the absolute temperature, S is the Seebeck coefficient, σ is the electrical conductivity, and κ is the thermal conductivity
We have investigated the thermoelectric properties of the 3C, 2H, 4H, and 6H polytypes of the wide-band-gap(n-type) semiconductors SiC, GaN, and ZnO based on first-principles calculations and Boltzmann transport theory
Our results show that the thermoelectric performance increases from 3C to 6H, 4H, and 2H structures with an increase of hexagonality for SiC

Summary

Introduction

Thermoelectric (TE) materials have attracted a lot of attention in recent years because of their ability to convert heat energy into electricity with reduced pollution.[1,2,3] The thermal–electricity conversion efficiency of TE materials is defined as the dimensionless figure of merit ZT = S2σT/κ, where T is the absolute temperature, S is the Seebeck coefficient, σ is the electrical conductivity, and κ is the thermal conductivity. Various strategies have been proposed to solve this problem, such as the phonon-glass behavior found in caged compounds,[4] grain boundaries,[5] band convergence,[6] nanostructures,[7,8] strong electron–phonon coupling by charge density waves,[9] and the liquid-like state.[10]

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