  Structural, resistivity, thermoelectric power and magneto-transport
properties of Cu doped Bi2Te3 topological insulators have been investigated.
The occurrence of the tuning of charge carriers from n type to p type by Cu
doping at Te sites of Bi2Te3 is observed both from Hall effect and
thermoelectric power measurements. Carrier mobility decreases with the doping
of Cu which provides evidence of the movement of Fermi level from bulk
conduction band to the bulk valence band. Thermoelectric power also
increaseswith doping of Cu.Moreover linear magnetoresistance (LMR) has been
observed at high magnetic field in pure Bi2Te3 which is associated to the
gapless topological surface states protected by time reversal symmetry (TRS),
whereas doping of Cu breaks TRS and an opening of band gap occurs which
quenches the LMR.
