Calculation of the High-Temperature Point Defects Structure in Te-Rich CdTe

Abstract

A thermodynamic equilibrium model for CdTe annealed under Te vapor is established, in which possible point defects and a defect reaction existing in undoped and In-doped Te-rich CdTe crystals are taken into consideration. Independent point defects, such as V_Cd, Cd_i, and Te_i, as well as defect complexes, namely Te_Cd-V_Cd (B complex), ${\hbox{Te}}_{\rm{Cd}}^{2 + }$-${\hbox{V}}_{\rm{Cd}}^{2 - }$ (D complex), ${\hbox{In}}_{\rm{Cd}}^{ + }$-${\hbox{V}}_{\rm{Cd}}^{ - }$ (A-center) and Te_i-V_Cd (Te_Cd), are discussed based on the defect chemistry theory. More specially, the mass action law and quasi-chemical equations are used to calculate defects concentration and Fermi level in undoped and doped CdTe crystals with different indium concentrations. It is found that the Fermi level is controlled by a ${\hbox{V}}_{\rm{Cd}}^{2 - }$, Te_Cd, and B/D-complex in undoped crystal. The concentration of V_Cd drops down in an obvious manner and that of Te_Cd rises for doped crystal with increasing [In].