A model for threshold voltage shift under negative gate bias stress in amorphous InGaZnO thin film transistors

E-ISSN： 1286-0050|72|3|30102-30102

ISSN： 1286-0042

Source： EPJ Applied Physics (The), Vol.72, Iss.3, 2015-12, pp. : 30102-30102

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Abstract

In the amorphous InGaZnO thin film transistors (a-IGZO TFTs) with high concentration of oxygen vacancy, the energy level of oxygen vacancy-related donor-like states in a-IGZO films near the gate insulator moves upwards under the negative gate bias stress (NGBS). The electrons in the donor-like states above the midgap are emitted to the conduction band, making the donor-like states positively charged. These positively charged donor-like states accumulate near the interface of the a-IGZO films and gate insulator and screen the gate voltage, thus leading to the negative shift of the threshold voltage (V_th) of a-IGZO TFTs. In this article we establish a physical model of V_th shift in the negative direction under NGBS, and the results are consistent with the experimental results.