The effects of electric field and gate bias pulse on the migration and stability of ionized oxygen vacancies in amorphous In–Ga–Zn–O thin film transistors

Oh, Young Jun; Noh, Hyeon‐Kyun; Chang, Kee Joo

doi:10.1088/1468-6996/16/3/034902

Cited by 20 publications

(9 citation statements)

References 46 publications

(54 reference statements)

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“…Similarly, the NBS instability has been explained by several possible mechanisms, namely, by charge trapping occurring at the dielectric interface [13,21], by positively charged oxygen vacancies [13,21,22], and by the diffusion of oxygen [23]. Finally, several causes have also been proposed for NBIS: charge trapping in the dielectric [12,13,24], driven by the ionization of oxygen vacancies [10,17,21,[25][26][27][28], trapping by zinc interstitials, and the formation of a hydrogen-related complexes [13], desorption of oxygen molecules or moisture [12,13], desorption of hydrogen [29], formation of oxygen interstitials [10,15], diffusion of hydrogen and charge trapping at the interfaces [30], formation of peroxides [31], and, finally, trapping of electrons in hydrogen bistable states [32].…”

Section: Introductionmentioning

confidence: 99%

Defects in Amorphous Semiconductors: The Case of Amorphous Indium Gallium Zinc Oxide

et al. 2018

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Based on a rational classification of defects in amorphous materials, we propose a simplified model to describe intrinsic defects and hydrogen impurities in amorphous indium gallium zinc oxide (a-IGZO). The proposed approach consists of organizing defects into two categories: point defects, generating structural anomalies such as metal-metal or oxygen-oxygen bonds, and defects emerging from changes in the material stoichiometry, such as vacancies and interstitial atoms. Based on first-principles simulations, it is argued that the defects originating from the second group always act as perfect donors or perfect acceptors. This classification simplifies and rationalizes the nature of defects in amorphous phases. In a-IGZO, the most important point defects are metal-metal bonds (or small metal clusters) and peroxides (O─O single bonds). Electrons are captured by metal-metal bonds and released by the formation of peroxides. The presence of hydrogen can lead to two additional types of defects: metal-hydrogen defects, acting as acceptors, and oxygen-hydrogen defects, acting as donors. The impact of these defects is linked to different instabilities observed in a-IGZO. Specifically, the diffusion of hydrogen and oxygen is connected to positive-and negative-bias stresses, while negative-bias illumination stress originates from the formation of peroxides.

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Section: Introductionmentioning

confidence: 99%

Defects in Amorphous Semiconductors: The Case of Amorphous Indium Gallium Zinc Oxide

et al. 2018

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“…Ionization of the oxygen vacancies has also been proposed to explain the PPC effect. 15 Zhou et al showed that the wavelength of light and the thickness of the passivation layer have a direct influence on the light-induced instabilities. 4 It is noteworthy that most of the reported oxides TFTs are enhancement-mode devices, which indeed brings immediate advantages to design high-gain circuits only with n-type transistors with minimum complexity.…”

mentioning

confidence: 99%

Improving positive and negative bias illumination stress stability in parylene passivated IGZO transistors

Kiazadeh

Gomes

Barquinha

et al. 2016

Applied Physics Letters

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The impact of a parylene top-coating layer on the illumination and bias stress instabilities of indium-gallium-zinc oxide thin-film transistors (TFTs) is presented and discussed. The parylene coating substantially reduces the threshold voltage shift caused by continuous application of a gate bias and light exposure. The operational stability improves by 75%, and the light induced instability is reduced by 35%. The operational stability is quantified by fitting the threshold voltage shift with a stretched exponential model. Storage time as long as 7 months does not cause any measurable degradation on the electrical performance. It is proposed that parylene plays not only the role of an encapsulation layer but also of a defect passivation on the top semiconductor surface. It is also reported that depletion-mode TFTs are less sensitive to light induced instabilities. This is attributed to a defect neutralization process in the presence of free electrons.

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“…We propose two plausible mechanisms for PBS instability with abnormal behavior after repeated mechanical stress in all directions, as shown in Figure (b). First, the N GD (V o 2+ ) increased by repeated mechanical stress can be gradually drifted into the back channel toward the electric field by positive gate bias to form additional current paths. , It has been reported that additional current paths other than main one (front channel) can degrade in subthreshold regions, such as the hump . Second, when positive gate bias is applied, hydrogen (H + ) may be introduced into mechanically degraded IGZO from Al 2 O 3 G.I.…”

Section: Resultsmentioning

confidence: 99%

“…First, the N GD (V o 2+ ) increased by repeated mechanical stress can be gradually drifted into the back channel toward the electric field by positive gate bias to form additional current paths. 35,36 It has been reported that additional current paths other than…”

Section: Resultsmentioning

confidence: 99%

Fatigue Effect of Stretchable a-InGaZnO TFT on PI/PDMS Substrate under Repetitive Uni/Biaxial Elongation Stress

Lee

Park

2022

ACS Appl. Electron. Mater.

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We examine the fatigue effects of repeated elongation stress for a fabricated a-IGZO thin-film transistor (TFT) on an island polyimide (PI)/poly(dimethylsiloxane) (PDMS) substrate. The repeated elongation stress evaluation was performed in both a uniaxial direction with 10, 30, and 50% strain and biaxial direction with 10, 20, and 30% strain for 50 000 cycles. The a-IGZO TFTs on the island PI exhibit the following parameters: Vth : −0.91 ± 0.30 V, μ sat : 26.3 ± 0.61 cm2/(V s), and SS: 0.40 ± 0.02 V/decade. As a result of the repeated elongation stress in the maximum evaluated elongation (uniaxis: 50% and biaxis: 30%), the subthreshold swing (SS) increased by about 0.20 V/decade in all directions, and the saturation mobility decreased only in the x-axis direction (Δμ sat : 26.30 → 21.43 cm2/(V s)). Through XPS analysis and TCAD simulation, it was confirmed that SS deteriorated due to an increase of the oxygen-vacancy-related defects (NGA and NGD ) in the IGZO channel layer after repeated elongation stress. The transmission line method (TLM) confirmed that contact resistance increased when stretched only in the x-axis direction. In addition, the positive bias stress (PBS) test showed abnormal behavior including an additional SS-degradation-induced Vth negative shift after repeated elongation stress in all directions. Consequently, the degradation mechanism of both the electrical properties and bias stability for the stretchable a-IGZO TFT was determined after elongation stresses.

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The effects of electric field and gate bias pulse on the migration and stability of ionized oxygen vacancies in amorphous In–Ga–Zn–O thin film transistors

Cited by 20 publications

References 46 publications

Defects in Amorphous Semiconductors: The Case of Amorphous Indium Gallium Zinc Oxide

Defects in Amorphous Semiconductors: The Case of Amorphous Indium Gallium Zinc Oxide

Improving positive and negative bias illumination stress stability in parylene passivated IGZO transistors

Fatigue Effect of Stretchable a-InGaZnO TFT on PI/PDMS Substrate under Repetitive Uni/Biaxial Elongation Stress

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