Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4

Abstract

Undercoordinated indium (In∗) is found to be an intrinsic defect that acts as a strong electron trap in amorphous InGaZnO 4. 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 InGaZnO 4. 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.