Doping with FeSe greatly enhances mobility in topological insulator Bi2Se3 single crystals

In this paper, we demonstrate a novel strategy to introduce Fe into a Bi2Se3 system through growth of crystals with nominal composition (FeSe)xBi2Se3. For x<0.04, Fe is shown to act mostly as a non-magnetic impurity; it uniformly enters the lattice and monotonically increases the c-lattice parameter, electronic doping level, and Shubnikov–de Haas mobility. The most striking observation is the record high Hall mobility of 8600 cm2/V s at 4.2 K for the smallest FeSe content (x=0.002) that further decreases with x. Elevated mobility is accompanied by a high residual resistance ratio and a rather moderate shift of Shubnikov–de Haas oscillations to a smaller field. These findings indicate that Fe admixture cures the point defects in Bi2Se3 and, thus, opens an effective way to suppress the defect subsystem in Bi2Se3-based topological insulator materials.