We report on the origin of threshold voltage shift with the thickness of amorphous InGaZnO channel layer deposited by rf magnetron sputter at room temperature, using density of states extracted from multi frequency method and falling rates of activation energy, which of trends are entirely consistent each other in respect of the reduction of total traps with increasing the channel thickness. Furthermore, we shows that the behavior of ⌬V th under the positive gate bias stress and thermal stress can be explained by charge trapping mechanism based on total trap variation.

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Effect of trap-density of amorphous InGaZnO thin film transistors (a-IGZO TFTs) were studied using different analysis of x-ray photoelectron spectroscopy (XPS) depth profile and density of states (DOSs). To change trap-densities systematically, rf-power was varied to cause different effect on the initial growth stage of a-IGZO layer grown on gate insulator. The interfacial trap-density was confirmed to be dominant effect on the performance and the threshold voltage shift of a-IGZO TFT by observing the variation of O1s binding energy from XPS. The relation between temperature stress induced and trap-density in deep level was investigated by analyzing DOSs.