First-principles investigation of the electronic and thermoelectric properties of SiGe doped with Sn and one percent B

Abstract

Silicon-Germanium (SiGe) has recently attracted much interest as a room temperature thermoelectric (TE) material for converting heat into electrical output power. With the advantage of silicon being non-toxic, cost-effective, and abundant on earth, a silicon base TE material has a promising future. A first-principle calculation based on the fully self-consistent Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA) to treat several forms of chemical disorders of SiGe by Sn-doping was carried out. In SiGe1-xSnx, as the Sn content increases the Fermi level shifts to the conduction band edge. Similarly, in Si1-xSnxGe, a high Sn content (x = 0.4 to 0.9) results in the Fermi level shifting to the conduction band edge. On the contrary, a low amount of Sn content (x = 0.1 to 0.3) causes the Fermi level to fluctuate between the conduction band and the valence band states. With the addition of 1% Boron impurity to the alloys Si1-xSnxGe and SiGe1-xSnx, the number of carriers (electron and hole) states was enhanced by 0.05 states/eV. This makes the alloys Si0.3Sn0.69B0.01Ge and SiGe0.4Sn0.59B0.01 promising for application as n-type electrodes in a thermoelectric generator (TEG).