Quantitative Dynamic\nEvolution of Unoccupied States\nin Hydrogen Diffused InGaZnSnO TFT under Positive Bias Temperature\nStress

Positive bias temperature stress (PBTS)-induced defects\nin self-aligned\ntop-gate coplanar amorphous indium–gallium–zinc–tin\noxide (a–IGZTO) thin-film transistors (TFTs) were quantitatively\nextracted as a function of hydrogen concentration. As the hydrogen\nconcentration increased, the device properties and stability improved.\nAs the stress time increased, the two decay constants that were extracted\nfrom the recovery of PBTS increased. Under PBTS, electrons were trapped\nin multiple defects simultaneously. Quantitative dynamic evolution\nof defect measurements showed that as the stress time increased, the\nactivation energy and density of defects changed. As electrons moved\nto the dielectric, the density of shallow-level defects in the channel\ndecreased, while the activation energy and density of deep-level defects\nincreased. With a higher hydrogen concentration in the channel, the\nchanges in defects were smaller. These findings indicate that hydrogen\nimproves stability by passivating electron trap sites.