  Compensation of intrinsic charges is widely used to reduce the bulk
conductivity of 3D topological insulators (TIs). Here we use low temperature
electron irradiation-induced defects paired with in-situ electrical transport
measurements to fine-tune the degree of compensation in Bi2Te3. The coexistence
of electrons and holes at the point of optimal compensation can only be
explained by bulk carriers forming charge puddles. These need to be considered
to understand the electric transport in compensated TI samples, irrespective of
the method of compensation.
