Electrical instabilities and low-frequency noise in InGaZnO thin film transistors

Our recent works concerning the electrical instability and low frequency noise (LFN) behaviors of a-IGZO TFTs are reviewed and significant results are reported. The experimental and modeling study of bias-stress-induced threshold voltage instabilities shows that the threshold voltage shift is mainly attributed to the electron injection from the channel into interface/dielectric traps in a-IGZO TFTs. By comparing the results from devices with different dielectrics, we find that the magnitude and time dependence of the threshold voltage shift are strongly dependent on the gate dielectric material in a-IGZO TFTs. The measured noise power spectral density shows that the LFN in a-IGZO TFTs obeys the classical 1/f noise theory, i.e., fits well to a 1/f^γ power law with γ ~ 1 in the low frequency range. From the dependence of normalized noise power spectral density on the gate voltage, the bulk mobility fluctuation is considered as a dominant LFN mechanism of a-IGZO TFTs in the linear operation regime.