Using first-principles method within the framework of the density functional
theory, we study the influence of native point defect on the structural and
electronic properties of Bi2​Se3​. Se vacancy in Bi2​Se3​ is a double
donor, and Bi vacancy is a triple acceptor. Se antisite (SeBi​) is always
an active donor in the system because its donor level (ε(+1/0))
enters into the conduction band. Interestingly, Bi antisite(BiSe1​) in
Bi2​Se3​ is an amphoteric dopant, acting as a donor when
μe​<0.119eV (the material is typical p-type) and as an acceptor when
μe​>0.251eV (the material is typical n-type). The formation energies
under different growth environments (such as Bi-rich or Se-rich) indicate that
under Se-rich condition, SeBi​ is the most stable native defect independent
of electron chemical potential μe​. Under Bi-rich condition, Se vacancy
is the most stable native defect except for under the growth window as
μe​>0.262eV (the material is typical n-type) and
ΔμSe​<-0.459eV(Bi-rich), under such growth windows one
negative charged BiSe1​ is the most stable one.Comment: 7 pages, 4 figure