Topological insulators (TIs) are a new class of quantum matter, with an insulating bulk, where electrons on the surface behave as massless Dirac fermions as in graphene [1,2]. However, in contrast with graphene, the surface state of TIs is topologically protected against non-magnetic disorder or lattice defects. This topological protection, unique to TIs, originates from the spin locked to the Fermi momentum ('spin-helical Dirac electrons', where backscattering is forbidden). Consequently, TI nanowire (NW) devices may outperform conventional semiconductor NWs or graphene nanoribbon (NR) devices that may suffer from backscattering. However, one of the main limitations to explore device applications in TIs was its large bulk conductance, shunting the surface conduction and also impeding effective gate tuning. © 2014 IEEE.