Field-effect mobility enhanced by tuning the Fermi level into the band gap of Bi${}_{2}$Se${}_{3}$

Rapid Communication

Field-effect mobility enhanced by tuning the Fermi level into the band gap of Bi $_{2}$ Se $_{3}$

Peng Wei, Zhiyong Wang, Xinfei Liu, Vivek Aji, and Jing Shi

Phys. Rev. B 85, 201402(R) – Published 9 May 2012

Abstract

By eliminating normal fabrication processes, we preserve the bulk insulating state of calcium-doped Bi $_{2}$ Se $_{3}$ single crystals in suspended nanodevices, as indicated by the activated temperature dependence of the resistivity at low temperatures. We perform low-energy electron beam irradiation ( $< 16$ keV) and electrostatic gating to control the carrier density and therefore the Fermi level position in the nanodevices. In slightly $p$ -doped Bi $_{2 - x}$ Ca $_{x}$ Se $_{3}$ devices, continuous tuning of the Fermi level from the bulk valence band to the band gap reveals an enhancement ( $>$ a factor of 10) in the field-effect mobility, which suggests suppressed backscattering expected for the Dirac fermion surface states in the gap of topological insulators.