Remote Doping of Sb Quantum Wells with Te

Antimony (Sb) has topological surface states, but its bulk band structure is semimetallic. Our goal is to study the transport properties of the topological states by suppressing the bulk conductivity through quantum confinement and enhancing the surface conductivity through remote n-type doping. A series of Sb quantum-well structures was grown by molecular beam epitaxy with Al_xGa_1-xSb barrier layers and GaAs (111) substrates. The Sb layer thickness of 4 nm was chosen to be thin enough to open a bandgap in the bulk band structure. To populate the topological electron states in the Sb quantum well, a section of one Al_xGa_1-xSb barrier was doped with Te atoms, which act as donor impurities. We report on Hall effect measurements that characterize the effectiveness of our approach in increasing the contribution of topological surface states to the conductivity of the structure.