Gate-tunable electronic transport in topological insulator Bi$_{2}$Te$_{3}$ thin films synthesized by metal-organic chemical vapor deposition

Topological insulator is a new state of matter with a nominally insulating gap in the bulk and non-trivial metallic states on the surface. One of the proto-type topological insulator materials, Bi$_{2}$Te$_{3}$, can be synthesized in the form of high quality, wafer scale thin films by metal-organic chemical vapor deposition (MOCVD). Here we present an experimental study of Bi$_{2}$Te$_{3}$ thin films with thickness ranging from a few nm's to 1 $\mu $m synthesized by MOCVD on semi-insulating GaAs (001) substrates. Hall bar shaped devices using atomic layer deposition (ALD) high-k Al$_{2}$O$_{3}$ or HfO$_{2}$ as gate dielectric have been fabricated. We have measured the magneto-transport (including both R$_{xx}$, 4-terminal longitudinal resistance, and R$_{xy}$, the Hall resistance) at various temperatures and gate voltages to probe the possible transport signatures of the topological surface states. We have also studied gate-tunable weak anti-localization in R$_{xx}$(B) for ultra-thin films.