We report on the electronic states and the transport properties of three-dimensional topological insulator (Bi1-xSbx)2Se3 ternary alloy thin films grown on an isostructural Bi2Se3 buffer layer on InP substrates. By angle-resolved photoemission spectroscopy, we clearly detected Dirac surface states with a large bulk band gap of 0.2-0.3 eV in the (Bi1-xSbx)2Se3 film with x = 0.70. In addition, we observed by Hall effect measurements that the dominant charge carrier converts from electron (n-type) to hole (p-type) at around x = 0.7, indicating that the Fermi level can be controlled across the Dirac point. Indeed, the carrier transport was shown to be governed by Dirac surface state in 0.63 x 0.75. These features suggest that Fermi-level tunable (Bi1-xSbx)2Se3-based heterostructures provide a platform for extracting exotic topological phenomena.
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