Behaviors of InGaZnO thin film transistor under illuminated positive gate-bias stress

Chen, Te-Chih; Chang, Ting‐Chang; Tsai, Chin-Hsien; Hsieh, Tien-Yu; Chen, Shih Ching; Lin, Chia-Sheng; Hung, Ming-Chin; Tu, Chun‐Hao; Chang, Jow‐Ran; Chen, Po-Lun

doi:10.1063/1.3481676

Cited by 172 publications

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“…10 Thin-film transistors made of amorphous oxide semiconductors exhibit a variety of metastable changes in their transistor characteristics through carrier doping and optical [11][12][13] or electrical [14][15][16][17][18][19][20][21] (or both [21][22][23][24][25][26][27][28] ) excitation of carriers. Indium (In)-based amorphous oxide semiconductors are considered as a promising material for next-generation thin-film electronics and optoelectronics because they have high electron mobility, transparency, flexibility and uniformity.…”

Section: Introductionmentioning

confidence: 99%

“…A negatively charged deep level has been hypothesized to be created in experiments, accompanied by a positive shift of the threshold voltage. 20 The experimentally measured thermal activation energy for electron trapping (E a,trap ) is in the range of 0.22-0.95 eV [15][16][17][18][19]22 under PBS and 0.08-0.14 eV 20 under CS. The α energy barrier in the (In*-M) 2 − formation corresponds to these values, which vary depending on the carrier concentration (Figure 4b).…”

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confidence: 99%

“…The measured values are E a,detrap = 0.23 and 0.97 eV. 22,19 The issue that a uniform background charge with PAW formalism gives rise to an additional total energy term has been recently addressed. 53 This term is not included in this study, and the energies obtained are only qualitative at best.…”

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confidence: 99%

“…In the range of n 4 10 20 cm − 3 , which is typical under PBS and CS conditions, the estimated α energy barriers are 0.0-1.4 eV in good agreement with the experiments (0.08-0.95 eV). [15][16][17][18][19][20]22 The thermal activation energy for electron detrapping (E a, detrap ) (after stopping the PBS or CS) has also been measured. This value can be interpreted as the β energy barrier in the (In*-M) 2 − → NS+2e − transition.…”

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Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4

Nahm

Kim

2014

NPG Asia Mater

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Undercoordinated indium (In*) is found to be an intrinsic defect that acts as a strong electron trap in amorphous InGaZnO 4 . Conduction electrons couple with the under-coordinated In* via Coulomb attraction, which is the driving force for the formation of an In*-M (M = In, Ga, or Zn) bond. The new structure is stable in the electron-trapped (2-) charge state, and we designate it as an intrinsic (In*-M) 2 − center in amorphous InGaZnO 4 . The (In*-M) 2 − centers are preferentially formed in heavily n-doped samples, resulting in a doping limit. They are also formed by electrical/optical stresses, which generate excited electrons, resulting in a metastable change in their electrical properties. NPG Asia Materials (2014) 6, e143; doi:10.1038/am.2014.103; published online 14 November 2014 INTRODUCTIONThe identification of charge-trapping defects on the atomic scale has been achieved in crystalline semiconductors. A donor can capture carrier electrons with large lattice relaxations, forming a DX (donor (D) deactivated (X)) center, 1-5 whereas an acceptor traps holes, forming an AX (acceptor (A) deactivated (X)) center. [5][6][7] However, in amorphous semiconductors, even though many charge-trapping phenomena that can modify electronic device characteristics 8 and be applied to nonvolatile memory devices 9 have been observed, the atomic and electronic structures of the charge-trapping defects lack clear understanding.Amorphous oxide semiconductors seriously suffer from chargetrapping events. 10 Thin-film transistors made of amorphous oxide semiconductors exhibit a variety of metastable changes in their transistor characteristics through carrier doping and optical [11][12][13] or electrical [14][15][16][17][18][19][20][21] (or both [21][22][23][24][25][26][27][28] ) excitation of carriers. Indium (In)-based amorphous oxide semiconductors are considered as a promising material for next-generation thin-film electronics and optoelectronics because they have high electron mobility, transparency, flexibility and uniformity. [29][30][31][32][33] However, the success of these applications has been limited by the lack of stability in their electrical properties owing to charge trapping.Investigation of the charge-trapping defects on the atomic scale is an essential prerequisite to overcome the instability issue of the indiumbased amorphous oxide semiconductors. An oxygen-vacancy (V O ) defect has been suggested as a metastable hole-trap center. 34,35 Unlike in crystalline oxides, V O and M-interstitial (M i ) (M = In, Ga, or Zn) are essentially indistinguishable in amorphous oxides. An M-M bond configuration can be understood as a V O and as anSimilarly, an O-O bond configuration can be interpreted as an M-vacancy (V M ) and as an In this paper, we find that undercoordinated indium (In*) acts as an intrinsic electron-trap center in In-based amorphous oxide semiconductors. Conduction electrons are subjected to a strong conductionelectron-ion interaction near the undercoordinated In* and trapped there, forming an In*-M bond. ...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4

Nahm

Kim

2014

NPG Asia Mater

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“…It was reported that the stability of a-IGZO TFTs suffered from several factors, such as the oxygen/water adsorption, temperature, illumination, and applied bias (14)(15)(16)(17). We have reported that the electrical degradation under the gate bias stress was mainly contributed by the charge trapping model and the influence of the ambient atmosphere involving the electric fieldinduced oxygen adsorption (18).…”

Section: Motivationmentioning

confidence: 95%

The Impact of Active Layer Pre-Treatment on Bias Stress Stability of Sol-Gel Derived Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistor

Chung¹,

Chang

Li³

et al. 2011

ECS Trans.

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We have investigated the gate bias stress-induced instability on the electrical properties with different pre-treatments for sol-gel derived amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFTs). The device with illuminating and heating pretreatments under the positive/negative gate bias stress in vacuum had the smallest threshold voltage shift as the stress duration increased, while the device with oxygen gas pre-treatment exhibited an obvious variation. These electrical instabilities were ascribed to the charge trapping in the gate insulator and the oxygen/water adsorption on the active layer. It indicates that the specific pre-treatment for the a-IGZO film can improve the device stability. It also provides the important information for the subsequent passivation process concerning the pre-treatment of the active layer.

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Photo‐Insensitive Amorphous Oxide Thin‐Film Transistor Integrated with a Plasmonic Filter for Transparent Electronics

Chang

Kim

et al. 2014

Adv Funct Materials

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3482www.MaterialsViews.com wileyonlinelibrary.com gate bias stress during most of the driving time and transparent devices are exposed to ambient light unavoidably. The stability resulting from electrical stress under light illumination is important since it can deteriorate the switching performances of a-IGZO-based TFTs. It was found that the positive bias illumination stress is insignifi cant compared to the negative bias illumination stress (NBIS). [ 7 ] NBIS has been explained by photo-induced carriers and the state transition, [7][8][9][10] but the exact mechanism is under debate. In addition, previous reports to improve the stability from NBIS are still insuffi cient from a device viewpoint.Herein we report a more practical use of a-IGZO-based TFTs by adopting plasmonic fi lters (PFs). Metal structures at the submicron scale demonstrate a unique optical response known as a surface plasmon (SP). A metallic fi lm with two dimensional nanohole arrays shows high transmission at the SP resonance frequency and the optical response related to this resonance phenomenon can be easily designed by the material and geometrical factors. This structural coloring technology using thin metal fi lms is superior in fi ltering performance compared to the conventional dye-based color fi lter that experiences degradation by heat and light due to the low chemical stability of the organic-dye material. In addition, thin and quasi-planar structures are advantageous in that they can be easily integrated with other devices. Therefore, PFs have recently been highlighted for use in industrial imaging applications such as CMOS image sensors and displays. [ 11,12 ] With this point of view, we suggest a novel AOS device that has possible applications in transparent electronics, by integrating a-IGZO-TFTs and PFs. A study on NBIS of the suggested a-IGZO-TFTs combined with PFs was performed. Unlike previous work with white or a monochromatic light source, the photosensitivity of a-IGZO-TFTs was investigated with the selectively controlled spectral range of the illumination by the PFs. The suggested TFTs showed extremely improved stability even under a NBIS environment. In addition, compared to the prior AOS TFTs which were equipped with equipped with metal shielding layer to block the light, [ 13 ] our suggestion provides not only the spectral selectivity from the light source but also reduces in the loss of transparency. We expect that the photosensitivity subdivided into spectral ranges will provide a practical guideline for designing structures or a fabrication process of transparent devices and enlarge the usage of AOS TFTs.Optical Characteristics of Plasmonic Filters : One of a prominent optical phenomena of nanohole arrays compared to that of micron scaled structures is extraordinary optical transmission [+] These authors contributed equally to this work. Photo-Insensitive Amorphous Oxide Thin-Film Transistor Integrated with a Plasmonic Filter for Transparent ElectronicsRecently, research interests in amorphous oxide semiconducto...

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Behaviors of InGaZnO thin film transistor under illuminated positive gate-bias stress

Cited by 172 publications

References 11 publications

Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4

Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4

The Impact of Active Layer Pre-Treatment on Bias Stress Stability of Sol-Gel Derived Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistor

Photo‐Insensitive Amorphous Oxide Thin‐Film Transistor Integrated with a Plasmonic Filter for Transparent Electronics

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