Gate-tunable transport properties of in situ capped Bi2Te3 topological insulator thin films

Combining of the ability to prepare high-quality, intrinsic Bi2Te3 topological insulator thin films of low carrier density with in situ protective capping, a pronounced, gate-tunable change in transport properties of Bi2Te3 thin films is demonstrated. Using a back gate, the carrier density is tuned by a factor of ≈7 in an Al2O3 capped Bi2Te3 sample and by a factor of ≈2 in Te capped Bi2Te3 films. Full depletion of bulk carriers is achieved, which allows access to the topological transport regime dominated by surface state conduction. When the Fermi level is placed in the bulk band gap, the presence of two coherent conduction channels associated with the two decoupled surfaces is observed. The magnetotransport results show that the combination of capping layers and electrostatic tuning of the Fermi level provide a technological platform to investigate the topological properties of surface states in transport experiments and pave the way toward the implementation of a variety of topological quantum devices.