P‐16: Light‐Bias Induced Instability and Persistent Photoconductivity in In‐Zn‐O/Ga‐In‐Zn‐O Thin Film Transistors

Ghaffarzadeh, Khashayar; Lee, Sungwon; Nathan, Arokia; Robertson, John; Jeon, Sanghun; Kim, Sang–Wook; Kim, Changjung; Chung, U‐In; Lee, Je‐Hun

doi:10.1889/1.3621030

Cited by 15 publications

(6 citation statements)

References 13 publications

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“…IGZO has oxygen vacancies at shallow donor states (V o + and V o 2+ ) and deep localized states (V o ) at 0.4–1 eV above E v 43,44. Therefore, optical stimulation generates electrons by ionization of oxygen vacancies (V o → V o 1+ + e − or V o → V o 2+ + 2e − ) 39,45,46. This process releases excess electrons into the bulk IGZO and increases its conductance.…”

Section: Figurementioning

confidence: 99%

Synergistic Improvement of Long‐Term Plasticity in Photonic Synapses Using Ferroelectric Polarization in Hafnia‐Based Oxide‐Semiconductor Transistors

2020

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A number of synapse devices have been intensively studied for the neuromorphic system which is the next‐generation energy‐efficient computing method. Among these various types of synapse devices, photonic synapse devices recently attracted significant attention. In particular, the photonic synapse devices using persistent photoconductivity (PPC) phenomena in oxide semiconductors are receiving much attention due to the similarity between relaxation characteristics of PPC phenomena and Ca2+ dynamics of biological synapses. However, these devices have limitations in its controllability of the relaxation characteristics of PPC behaviors. To utilize the oxide semiconductor as photonic synapse devices, relaxation behavior needs to be accurately controlled. In this study, a photonic synapse device with controlled relaxation characteristics by using an oxide semiconductor and a ferroelectric layer is demonstrated. This device exploits the PPC characteristics to demonstrate synaptic functions including short‐term plasticity, paired‐pulse facilitation (PPF), and long‐term plasticity (LTP). The relaxation properties are controlled by the polarization of the ferroelectric layer, and this polarization is used to control the amount by which the conductance levels increase during PPF operation and to enhance LTP characteristics. This study provides an important step toward the development of photonic synapses with tunable synaptic functions.

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Section: Figurementioning

confidence: 99%

Synergistic Improvement of Long‐Term Plasticity in Photonic Synapses Using Ferroelectric Polarization in Hafnia‐Based Oxide‐Semiconductor Transistors

2020

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“…This can be caused by the photoionization of the deep oxygen vacancy (V O ) to shallow ionized oxygen vacancies (V O 2þ ). 20 The formed V O 2þ will be pulled to the channeldielectric interface by application of negative gate bias stress. This defect conversion increases IGZO free carrier concentration and consequently brings a negative shift of V th .…”

Section: à2mentioning

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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“…) has also been accepted by more and more researchers. [15][16][17][18] It should be noted that quite many related studies have only focused on the a-IGZO TFTs without passivation, but in real production passivation is essential to ensure devices' stability by keeping their active layers from interacting with external environments. 17,19,20) Therefore, investigating the dependence of light illumination stability properties on passivation layers of a-IGZO TFTs is meaningful for mass production of this novel technology.…”

Section: +mentioning

confidence: 99%

Light illumination stability of amorphous InGaZnO thin film transistors with sputtered AlO_xpassivation in various thicknesses

Zhou

et al. 2014

Jpn. J. Appl. Phys.

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Light illumination stability of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) passivated by sputtered AlO x thin films were investigated in this paper. Light wavelength and passivation-layer thickness were intentionally controlled to ascertain the related two physical mechanisms, i.e., electron-hole pair (EHP) generation and oxygen vacancy (V O ) formation. A qualitative model was proposed to effectively compare and distinguish the above two mechanisms in thermal stability of a-IGZO TFTs with passivation layers. With light wavelength decreasing EHP generation became evident where the "threshold wavelength" was between 420 and 400 nm for the a-IGZO TFTs used in this study. Meanwhile, passivation-layer could significantly improve the stability of a-IGZO TFTs under long-wavelength light illumination by suppressing the escape of oxygen atoms to form V O in a-IGZO films. The "threshold thickness" of AlO x passivation-layer in our devices was estimated to be about 90 nm.

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P‐16: Light‐Bias Induced Instability and Persistent Photoconductivity in In‐Zn‐O/Ga‐In‐Zn‐O Thin Film Transistors

Cited by 15 publications

References 13 publications

Synergistic Improvement of Long‐Term Plasticity in Photonic Synapses Using Ferroelectric Polarization in Hafnia‐Based Oxide‐Semiconductor Transistors

Synergistic Improvement of Long‐Term Plasticity in Photonic Synapses Using Ferroelectric Polarization in Hafnia‐Based Oxide‐Semiconductor Transistors

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

Light illumination stability of amorphous InGaZnO thin film transistors with sputtered AlO_xpassivation in various thicknesses

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P‐16: Light‐Bias Induced Instability and Persistent Photoconductivity in In‐Zn‐O/Ga‐In‐Zn‐O Thin Film Transistors

Cited by 15 publications

References 13 publications

Synergistic Improvement of Long‐Term Plasticity in Photonic Synapses Using Ferroelectric Polarization in Hafnia‐Based Oxide‐Semiconductor Transistors

Synergistic Improvement of Long‐Term Plasticity in Photonic Synapses Using Ferroelectric Polarization in Hafnia‐Based Oxide‐Semiconductor Transistors

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

Light illumination stability of amorphous InGaZnO thin film transistors with sputtered AlOxpassivation in various thicknesses

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Light illumination stability of amorphous InGaZnO thin film transistors with sputtered AlO_xpassivation in various thicknesses