Undercoordinated indium (In*) is found to be an intrinsic defect that acts as a strong electron trap in amorphous InGaZnO4. Conduction electrons couple with the under-coordinated In* via Coulomb attraction, which is the driving force for the formation of an In*–M (M=In, Ga, or Zn) bond. The new structure is stable in the electron-trapped (2–) charge state, and we designate it as an intrinsic (In*–M)2− center in amorphous InGaZnO4. The (In*–M)2− centers are preferentially formed in heavily n-doped samples, resulting in a doping limit. They are also formed by electrical/optical stresses, which generate excited electrons, resulting in a metastable change in their electrical properties.
- Ho-Hyun Nahm
- Yong-Sung Kim
