Native point defects and low p-doping efficiency in Mg2(Si,Sn) solid solutions: A hybrid-density functional study

We perform hybrid-density functional calculations to investigate the charged defect formation energy of native point defects in Mg2Si, Mg2Sn, and their solid solutions. The band gap correction by hybrid-density functional is found to be critical to determine the charged defect density in these mater...

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Bibliographic Details
Published in:Journal of alloys and compounds 2021-02, Vol.853, p.157145, Article 157145
Main Authors: Ryu, Byungki, Choi, Eun-Ae, Park, Sungjin, Chung, Jaywan, de Boor, Johannes, Ziolkowski, Pawel, Müller, Eckhard, Park, SuDong
Format: Article
Language:English
Subjects:
Charge compensation
Compensation
Conductivity
Current carriers
Density
Doping
Doping efficiency
Energy of formation
Free energy
Heat of formation
Hybrid-DFT
Intermetallic compounds
Interstitials
Magnesium compounds
Metal silicides
Native defects
Point defects
Solid solutions
Stannides
Thermal degradation
Thermoelectric
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Summary:We perform hybrid-density functional calculations to investigate the charged defect formation energy of native point defects in Mg2Si, Mg2Sn, and their solid solutions. The band gap correction by hybrid-density functional is found to be critical to determine the charged defect density in these materials. For Mg2Si, Mg interstitials are dominant and provide unintentional n-type conductivity. Additionally, as the Mg vacancies can dominate in Mg-poor Mg2Sn, p-type conductivity is possible for Mg2Sn. However, the existence of low formation energy defects such as MgSn1+ and IMg2+ in Mg2Sn and their diffusion can cause severe charge compensation of hole carriers resulting in low p-type doping efficiency and thermal degradation. Our results indicate that, in addition to the extrinsic doping strategy, alloying of Mg2Sn with Mg2Si under Mg-poor conditions would be necessary to enhance the p-type conductivity with less charge compensation. •Native point defects in Mg2Si and Mg2Sn alloys are studied.•First principles calculations were performed with hybrid-functional.•Band gap correction is critical for defect stability.•Hole carriers are easily compensated by native point donors.•Origin of p-doping difficulty and thermal degradation were discussed.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2020.157145