In this study, the oxygen flow rate (OFR) dependence of negative bias illumination stress (NBIS) and positive bias stress (PBS) in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) devices was investigated. Unlike in previous studies, our study simultaneously considered and analyzed the bias stress-induced degradation mechanisms by charge trapping and defect creation. NBIS and PBS instability were measured according to the OFR splits of bottom-gate (BG) IGZO TFTs and the behavior of full subgap range density of states (DOS) was experimentally tracked with especial emphasis on deep-level oxygen vacancy (

${V}_{\text {O}}$

) peak. It was found that the observed DOS variation was consistent with the

${V}_{\text {O}}$

ionization model during NBIS. In addition, the threshold voltage shift by charge trapping (

${\Delta } {V}_{\text {T,CT}}$

) and the threshold voltage shift by defect creation, i.e., change of DOS, (

${\Delta } {V}_{\text {T,DOS}}$

) were separated and extracted through the subthreshold slope decomposition method. After NBIS, the threshold voltage shift (

${\Delta } {V}_{\text {T}}$

) was composed of a component by charge trapping and a component with the ionization of

${V}_{\text {O}}$

. After PBS,

${\Delta } {V}_{\text {T}}$

was dominated by a component arising due to charge trapping. Fitting through the stretched exponential function (SEF) was performed for each separately extracted

${\Delta } {V}_{\text {T}}$

, and the activation energy for each

${\Delta } {V}_{\text {T}}$

was extracted using the inverse Laplace transform method through the extracted

${\Delta } {V}_{\text {T0}}$

$\tau $

, and

$\beta $

. Activation energy by charge trapping and DOS was extracted from NBIS and PBS, respectively. As a result of simultaneously considering the two degradation mechanisms, the extracted activation energy was located between the previous values. Experimentally extracted sets of DOS-specific parameters before and after bias stress were applied to technology computer-aided design (TCAD) simulations. Accurate reproduction of TFT current–voltage (

${I}$

–

${V}$

) curves before and after bias stress and recovery suggests that the methodology and parameter set used in this study are reasonable and potentially useful for a more robust and systematic analysis of the bias stress-induced instability in a-IGZO BG TFTs.

#	Concept	H-Index	Publications	Citations
1	Engineering	1	1	46
2	Applied Physics	1	1	46
3	Electrical Engineering	1	1	46
4	Physics	1	1	46
5	Condensed Matter Physics	1	1	46

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