  Magneto-transport measurements have been carried out on Bi2-xSbxSe3 (x = 0,
0.05, 0.1, 0.3, 0.5) single crystals at 4.2 K temperature in the magnetic field
range of -15 T to 15 T. Shubnikov-de Haas (SdH) oscillations of 2D nature were
observed in samples with Sb concentration upto x = 0.3. The analyses of SdH
oscillations observed in magneto-resistance data using Lifshitz-Kosevich
equation reveal a systematic decrease in the Fermi surface area with Sb
substitution. The Berry phase obtained from the Landau Level fan diagram
suggests the occurrence of 2D oscillations arising from a Topological Surface
State (TSS) for Sb concentrations of x = 0, 0.05 and 0.1; while 2D oscillation
seen at higher Sb concentration is attributed to surface 2D electron gas
consequent to downward band bending.
