View article

The role of defects in materials is one of the long-standing issues in solid-state chemistry and physics. On one hand, intrinsic ionic disorder involving stoichiometric amounts of lattice vacancies and interstitials is known to form in highly ionic crystals, eg, Frenkel disorder in CaF2 and Schottky disorder in NaCl. 1 On the other hand, intrinsic electronic disorder occurs in traditional semiconductor materials involving electron and hole carriers, eg, thermal band gap excitations in Si or Ge. 2 The difficulty arises intermediate of these two regimes, for materials that fall between the large band gap ionic solids and small band gap covalent semiconductors: the case of wide band gap semiconductors. These materials can exhibit a combination of ionic and electronic conduction and have applications ranging from optoelectronic devices 3, 4 (eg, exploiting the coexistence of optical transparency and electrical conduction in …