Temperature and carrier concentration dependence of thermoelectric properties of GeBi4Te7

• Published in: Journal of the Korean Physical Society Vol. 74; no. 3; pp. 256 - 260
• Main Authors: Quang, Tran Van, Kim, Miyoung
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Physical Society 01-02-2019; Springer Nature B.V; 한국물리학회
• Subjects: Anisotropy; Approximation; Carrier density; Density functional theory; Doping; Electronic structure; Energy gap; Mathematical analysis; Mathematical and Computational Physics; Particle and Nuclear Physics; Physics; Physics and Astronomy; Power factor; Seebeck effect; Temperature dependence; Theoretical; Thermoelectricity; 물리학; Electronic structures; First-principles calculations; Ferromagnetic
• ISSN: 0374-4884; 1976-8524
• DOI: 10.3938/jkps.74.256

We investigate the temperature and carrier concentration dependence of thermoelectric properties including the Seebeck coefficient and thermoelectric power factor of GeBi
4
Te
7
compound by the
ab initio
electronic structure calculations within density functional theory (DFT). The DFT Kohn-Sham equation is solved by employing the local density approximation (LDA) as well as the screened-exchange local density approximation (sX-LDA). We obtain a band gap of 0.13 eV in sX-LDA for GeBi
4
Te
7
while the LDA calculation predicts a metallic electronic structure due to its well-known bandgap underestimation problem. The optimal concentration to maximize the thermoelectric power factor is found to be 1.8 × 10
20
cm
−3
for
p
-type doping and 3.0 × 10
20
cm
−3
for n-type doping at room temperature, yielding the power factors of 10.2 and 8.2 μWcm
−1
K
−2
, respectively. Anisotropy of transport coefficients also depends on the doping type indicating that the in-plane and the perpendicular direction is preferred in
p
-type and n-type doping, respectively.