Gate tuned weak antilocalization effect in calcium doped Bi2Se3 topological insulators

•High quality single crystals of Bi1.995Ca0.005Se3 show p-type behavior in bulk.•HLN fitting of magneto-conductance data gives −0.75≤α≤−1.12as+30V≤Vg≤−30V.•Device prepared from parent crystal of Bi1.995Ca0.005Se3 shows an n-type behavior.

We investigate the effect of weak antilocalization arising from topological surface states in high quality single crystals of Bi1.995Ca0.005Se3, at low temperature. The weak antilocalization co-efficient of conductance can be tuned by gate voltage and separated into coherently independent channels, which in topological insulators include both the bulk conduction and topological surface conduction. By calcium doping, we are able to achieve p-type behavior in Bi1.995Ca0.005Se3 (bulk crystals of thickness ~0.3 mm) with carrier density ~1018/cm3~1018/cm3.