Structural and electronic properties of interstitial oxygen defect in amorphous indium gallium oxide (IGO) semiconductors: a theoretical study

Abstract We elucidate the role of gallium (Ga) in the structural and electronic properties of amorphous indium gallium oxide (a-IGO) for different Ga concentrations with oxygen interstitial defects using hybrid density functional methods. Ab initio molecular dynamic simulations reveal that Ga substitution significantly affects the structural characteristics, and that Ga–O coordination is particularly sensitive to changes in oxygen stoichiometry. The electronic structure indicates the formation of an O–O dimer in the neutral state. The stability of this dimer upon capturing electrons is influenced by the local atomic structure around the dimer. When the bond breaks, the dimer’s antibonding defect level is significantly lowered from the conduction band, approaching the valence band. This makes it more energetically advantageous for the dimer to capture two electrons. We statistically studied the Ga concentration dependence on the impact of O 2 dimer generation in a-IGO. Formation transition energy indicates that O–O bond is broken easily with more Ga, which acts as an electron trap identifying the origin of positive bias stress observed in the transistor behavior.