  We show Shubnikov-de Haas oscillations in topological insulator
(Bi$_{x}$Sb$_{1-x}$)$_{2}$Te$_{3}$ films whose carrier type is p-type (x =
0.29, 0.34) and n-type (x = 0.42). The physical properties such as the Berry
phase, mobility, and the scattering time are significantly changed by tuning
the Fermi-level position with the concentration x. The Landau-level fan diagram
in the sample with x = 0.42 showed the $\pi$ Berry phase and its mobility was
as high as 17,000 cm$^{2}$/V/s, whereas the others had the 2$\pi$ Berry phase
and much lower mobility. This suggests that because the bulk band of the sample
with x = 0.42 does not cross the Fermi level, it becomes bulk insulating,
resulting in the topological surface-state dominating transport. Thus, we can
switch sample properties from degenerate to bulk insulating by tuning the
concentration x, which is consistent with results of angle-resolved
photoemission spectroscopy.
