Doping and Defect Structure of Tetradymite-Type Crystals

Abstract

Nonstoichiometry of tetradymite-type crystals A 2 V B 3 VI that are grown from stoichiometric melts leads to the formation of native defects in the crystal lattice (predominantly antisite defects, A B À1 and vacancies V B +2 in the anion sublattice). This paper summarizes the basic ideas concerning a point defect model in A 2 V B 3 VI crystals. It turns out that a variety of doping elements interact with the native defects. Such interactions alter the concentration of free charge carriers, affect the doping efficiency, and modify the transport properties. Detailed understanding of the defect structure in tetradymite-type crystals is very important as it impacts on the efficiency of these materials when used as active elements in thermoelectric coolers.

Nonstoichiometric doping and Bi antisite defect in single crystal Bi2Se3

“…[13] In addition to the finding of intercalated Bi 2 -layer patches, as revealed in Fig. 2(c), we also observed Bi Se antisite defects in the bulk of ∼25 nm thickness along the incident beam direction, as shown in Fig.…”

“…The importance of antisite defect in the tetradymitetype compounds has been discussed in the scope of narrow band gap semiconductor previously, [13] yet quantitative evidence is difficult to obtain at the point defect level. Considering the number of outer shell electrons for Bi(6s 2 6p 3 ) and Se(4s 2 4p 4 ), simple argument borrowed from extrinsic semiconductor suggests that Bi Se antisite can be an acceptor.…”

Emergent surface superconductivity in the topological insulator Sb2Te3

“…In Sb 2 Te 3 vacancies on cation (Sb) or anion (Te) sites respectively act as electron donors and acceptors. From the detailed studies of these materials 17,50 we know that growth conditions using stoichiometric ratio starting materials result in slightly Te poor crystals, Sb 2 Te 3-x with xE0.03-0.05. Also, native concentrations of Sb antisites (contributing one hole each) and Te vacancies (contributing two electrons each) are B10 20 cm À 3 and 2 Â 10 19 cm À 3 , respectively, consistently accounting for the observed Hall number and other material properties 17,18 .…”

Two-Dimensional Colloidal Nanocrystals

“…314 In this phase of the matter, the bulk material is expected to be an insulator, while surface conducting states are formed. The obtained plates tend to present some antistructural defects [324][325][326] where in the case of Sb2Te3, Te atoms replace some of the cations which tends to result in a p-type doping. 327 Bi2Se3 is generally n doped because of similar defects.…”