Comparative study on light-induced negative-bias stress stabilities in amorphous In-Ga-Zn-O thin film transistors with photoinduced transient spectroscopy

A comparative study on light-induced negative-bias stress stabilities in amorphous In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) was performed by means of photoinduced transient spectroscopy (PITS). When the a-IGZO thin films were deposited with 4% O2 partial pressure (P/P), a dominant peak with a maximum of around 100 K was clearly observed from the sample. There was a flow rate of SiH4/N2O of 4/100 sccm for the ESL deposition, while the PITS spectra from the sample with a flow rate of SiH4/N2O of 6/150 sccm possessed a broader peak of around 115 K and an apparent shoulder of around 200-280 K was observed. This shoulder of around the 200-280 K was clarified when the a-IGZO thin film was deposited with an O2 P/P of 20 % In accordance with the changes in the electronic structures in the a-IGZO thin films due to the ESL deposition, the stability of the TFTs against the negative bias thermal Illumination stress (NBTIS) was degraded; the value of the Vth shift after the 2h-NBTIS test was increased from 2.5 to 6.0 V The decreasing the compensating acceptors and/or the increasing the hydrogen-related donors could be the origin of the negative Vth shift during the NBTIS test.