Electronic and thermoelectric properties of the group-III nitrides (BN, AlN and GaN) atomic sheets under biaxial strains

• 1、Department of Physics, Xiamen University, Xiamen 361005, China
• 2、Xiamen University Malaysia Campus, 439000 Sepang, Selangor, Malaysia
• 3、Institute of High Performance Computing, Agency for Science, Technology and Research, 1 10 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Republic of Singapore
• 4、Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen University, Xiamen 361005, China

Abstract：Based on first-principles methods and Boltzmann transport theory, we investigated the biaxial strain effects on electronic and thermoelectric properties of three group-III nitrides (BN, AlN and GaN) 2D honeycomb nanosheets. The direct-indirect band gap transitions occurred for BN and GaN nanosheets when the strain is applied. In addition, the band gaps decrease with increase of tensile strain. By the total and projected density-of-state (PDOS) analyses, we also tried to uncover the mechanism behind. The carrier mobility and average relaxation time are studied by deformation potential method. It was found that n-type BN, p-type AlN and p-type GaN show relatively large ZT values at room temperature. At the same time, we presented the contour plots of their electrical transport properties as a function of both temperature and carrier concentration at strain-free states. Power-factors and relaxation times of BN, AlN and GaN nanosheets were also calculated. We found only peak power factors of p-type GaN and n-type BN show a strong dependence on biaxial strain. Such differences of the strain-dependent thermoelectric performance among BN, AlN and GaN may be due to the competition between covalency and ionicity in these 2D structures. Our results provide a new avenue to optimize thermoelectric properties of 2D nanosheets by strain engineering.

keywords： Density functional theory thermoelectric group-III nitrides nanosheets

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