Possible n–type carrier sources in In₂O₃(ZnO)_k

Homologous compounds with the formula In 2 O 3 (ZnO) k, where k is an integer, have potential applications as transparent conducting oxides and high temperature thermoelectric materials. In this study, we focus on the defect properties. Using the k = 3 phase as a prototype, we calculate with the first-principles method the defect formation energies and transition levels of the most probable n -type carrier producers, which include oxygen vacancy (V O ), indium antisite on zinc (In Zn ), indium interstitial (In i ), and zinc interstitial (Zn i ). The site-preference of these defects has been explored by comparing the total energies of defects at different sites. Under the n -type environment, In Zn has a low formation energy and meanwhile a transition energy level close to the conduction band minimum (CBM); V O also has a lower formation energy, however a deep transition energy level in the band gap; the cation interstitials have high formation energies, although their defect transition energy levels are quite shallow. Besides, we find that V O and In Zn tend to form a defect complex when the two isolated defects take the nearest-neighboring atomic sites in the same ab -plane. We conclude that In Zn and its related defect-complex are the possible n –type carrier sources in In 2 O 3 (ZnO) k . Besides, we found that V O has a significant site-preference, which can modify the site-preference of In Zn by forming defect-complexes. This may lead to high anisotropy in relaxation time, and then the experimentally reported strong anisotropy in electrical conductivities in In 2 O 3 (ZnO) 5 .