Anisotropic Seebeck and magneto-Seebeck coefficients of Bi and Bi0.92Sb0.08 alloy thin films

We have grown Bi and BiSb alloy thin films on (211)CdTe substrates by molec ular beam epitaxy. Growth proceeds with the Bi or BiSb (00.1) axis oriented along the CdTe[111] direction, which is tilted by 19 degrees with respect to the substrate normal. Measurements of the Seebeck coefficient reveal a s trong dependence on angle within the plane, due to the anisotropic electron ic structure. The coefficient measured along the [(1) over bar 11] axis, wh ich includes a trigonal contribution from the Seebeck tensor, is considerab ly higher than the value along the [01(1) over bar] axis. The magneto-Seebe ck coefficient was also studied, for magnetic fields of 0-0.7 T. We observe a strong dependence on both crystal-axis and magnetic field direction, the so-called "umkehr" effect. (C) 2000 American Institute of Physics. [S0021- 8979(00)06714-1].