The Thermoelectric Properties of -Type Bismuth Telluride: Bismuth Selenide Alloys
Fermi surface maps in the bisectrix plane illustrate the variation in positions and energies of the conduction band extrema with alloy composition. In Bi2Se3 (a), the CBM is singly degenerate at , while in Bi2Te3 (c), the CBM is at the sixfold f point slightly displaced from the line with a second twofold pocket at z along the line. In alloys near Bi2Te2.5Se0.5 (b), the pockets at f and z are at almost the same energy level. Varying the alloy composition manipulates the magnitude of the spin-orbit interaction and shifts the energy and positions of various extrema. This is illustrated in (d) where doubling the spin-orbit interaction in Bi2Se3 calculations results in a CBM at f as in Bi2Te3.