Effect of ordered arrays of native defects on the crystal structure of In- and Ga-rich Cu-ternaries

A comparative study of the unit cell parameters a and c, and volume V of the chalcopyrite-related of In- and Ga-rich ordered defect compounds of the ternary systems Cu-In-Se, Cu-In-Te, Cu-Ga-Se, and Cu-Ga-Te is presented. It is observed that these parameters decrease in the sequence 1:1:2→3:5:9→5:9:16→2:4:7→1:3:5→1:5:8. This behavior is attributed to the presence of arrays of ordered defects in the crystal lattice of these compounds. It is also found that values of a, c, and V in these systems vary linearly with the fraction m of [2 VCu−1+(In,Ga)Cu+2] defect pair for each unit of Cu(In,Ga)(Se2,Te2).