Effective Fermi level tuning of Bi2Se3 by introducing CdBi/CaBi dopant

Abstract

By using a first-principles method within the framework of density functional theory, we study the formation energies of Cd and Ca dopants in Bi₂Se₃. The calculation results show that Cd_Bi and Ca_Bi are the most stable defects for Cd and Ca dopants in Bi₂Se₃, respectively. Additionally, both the Cd_Bi and Ca_Bi defects in Bi₂Se₃ are p-type dopants, with accepter levels at ε(0/−1) = 0.030 eV and ε(0/−1) = 0.028 eV, respectively. Comparing their formation energies with that of the native defects under a different growth condition, Cd_Bi and Ca_Bi can effectively compensate the n-type native defects, V_Se and Se_Bi, under Se-rich growth conditions. It is interesting to note that such compensation effects become weaker, gradually, with the growth conditions changing from Se-rich to Bi-rich. Therefore, a p-to-n or n-to-p type conversion for Bi₂Se₃ can be achieved by changing the growth conditions. Simultaneously, the Fermi level, which is determined by the charge neutrality condition, can be effectively tuned, which is in agreement with previous experimental reports.