Density of trap states measured by photon probe into ZnO based thin-film transistors

Lee, Kimoon; Ko, Gunwoo; Lee, Gun Hwan; Han, Gi Bok; Sung, Myung Mo; Ha, Tae Woo; Kim, Jae-Hoon; Im, Seongil

doi:10.1063/1.3483763

Cited by 34 publications

(9 citation statements)

References 14 publications

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“…Since electrons trapped at deeper interface states have to be released by photons with higher energy, the corresponding DV th as a function of illumination wavelength can be used to extract the density profile of interfacial states. 10 Second, although the transfer curves plotted in logarithmic scale are nearly parallel to each other in long illumination wavelength range, the SS of the TFT exhibits apparent increase at shorter wavelength. Figure 3 shows the SS values as a function of illumination wavelength revealing a turning point at $ 625 nm, after which the SS continuously increases.…”

mentioning

confidence: 90%

Electrical instability of amorphous indium-gallium-zinc oxide thin film transistors under monochromatic light illumination

Huang¹,

Wu²,

Lu³

et al. 2012

Appl. Phys. Lett.

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The electrical instability behaviors of a positive-gate-bias-stressed amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistor (TFT) are studied under monochromatic light illumination. It is found that as the wavelength of incident light reduces from 750 nm to 450 nm, the threshold voltage of the illuminated TFT shows a continuous negative shift, which is caused by photo-excitation of trapped electrons at the channel/dielectric interface. Meanwhile, an increase of the sub-threshold swing (SS) is observed when the illumination wavelength is below 625 nm ($2.0 eV). The SS degradation is accompanied by a simultaneous increase of the field effect mobility (l FE) of the TFT, which then decreases at even shorter wavelength beyond 540 nm ($2.3 eV). The variation of SS and l FE is explained by a physical model based on generation of singly ionized oxygen vacancies (V o þ) and double ionized oxygen vacancies (V o 2þ) within the a-IGZO active layer by high energy photons, which would form trap states near the mid-gap and the conduction band edge, respectively.

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mentioning

confidence: 90%

Electrical instability of amorphous indium-gallium-zinc oxide thin film transistors under monochromatic light illumination

Huang¹,

Wu²,

Lu³

et al. 2012

Appl. Phys. Lett.

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“…I D -V G hysteresis and subthreshold slope analysis on TFTs report N it values from ∼2.7 × 10 11 to 5.38 × 10 12 cm −2 for ZnO/HfO 2 [1], [5] and 2.47 × 10 12 cm −2 for Ta 2 O 5 /ZnO [7]. Photoexcited trap-charge collection spectroscopy on Al 2 O 3 /PVP/ZnO structures has been also studied, where D it peaks at 1.31 and 1.37 eV below the conduction band (E C ) were reported with values of 1 × 10 13 and 5.1 × 10 12 cm −2 · eV −1 , respectively [9]. In this letter, the density and energy distribution of electrically active defect states in ZnO/HfO 2 structures is reported based on the admittance spectroscopy (AS) method.…”

Section: Introductionmentioning

confidence: 96%

Admittance Spectroscopy of Interface States in $ \hbox{ZnO/HfO}_{2}$ Thin-Film Electronics

Siddiqui

Phillips

Leedy

et al. 2011

IEEE Electron Device Lett.

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The electronic properties of ZnO/HfO 2 interface states are studied by dc current-voltage and ac admittance spectroscopy on thin-film transistors (TFTs) and metal-insulatorsemiconductor capacitor structures. Subthreshold behavior of the transistors indicates an interface state density (N it ) value of 7.2 × 10 12 cm −2 . Cole-Cole plots of ac admittance demonstrate Debye behavior and extracted energy-dependent interface state density (D it ) with an approximate exponential decay of 3.0 × 10 13 cm −2 · eV −1 near the conduction band to 1.2 × 10 12 cm −2 · eV −1 at 0.9 eV below the conduction band. The integrated interface state density from these measurements is N it = 7.9 × 10 12 cm −2 , which is consistent with the value obtained from subthreshold behavior of the TFTs.Index Terms-Admittance spectroscopy (AS), hafnium oxide (HfO 2 ), interface charge density, zinc oxide (ZnO).

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“…It is suggested that the generation of hydroxyl groups serving as electron traps at channel/dielectric interface could be the main origin of this V th shift , but the detailed physics that are responsible for this have not yet been clarified. Recently, we developed the novel technique of photo‐excited charge‐collection spectroscopy (PECCS) for probing the interfacial trap states . The density of states (DOS) of the interfacial traps could be directly mapped as a function of the photon energy by tracking the change in photo‐induced V th values.…”

Section: Introductionmentioning

confidence: 99%

Origin of channel/dielectric interfacial trap states modification by ultraviolet irradiation on organic thin-film transistors

Lee

2014

Phys. Status Solidi A

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The authors report on the origin of channel/dielectric interfacial states modified by ultraviolet (UV) irradiation on pentacene thin-film transistors (TFTs) with poly-4-vinylphenol and AlO x double gate dielectric. Exposing the device to 352 nm UV irradiation on caused a positive threshold voltage (V th ) shift, and then photo-excited charge-collection spectroscopy (PECCS) was applied to the device to clarify the changes of the interfacial density of states (DOS) as the origin of V th modification. From the PECCS measurement, it could be probed that there was a drastic decrease in DOS for deep traps at $1.31 and $1.38 eV above the highest occupied molecular orbital level of pentacene. Consequently, we can conclude that the positive shift of V th for pentacene-TFT by UV irradiation results from the elimination of deep hole traps, which could be introduced by the interfacial dipoles at the channel/dielectric interface.

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Density of trap states measured by photon probe into ZnO based thin-film transistors

Cited by 34 publications

References 14 publications

Electrical instability of amorphous indium-gallium-zinc oxide thin film transistors under monochromatic light illumination

Electrical instability of amorphous indium-gallium-zinc oxide thin film transistors under monochromatic light illumination

Admittance Spectroscopy of Interface States in $ \hbox{ZnO/HfO}_{2}$ Thin-Film Electronics

Origin of channel/dielectric interfacial trap states modification by ultraviolet irradiation on organic thin-film transistors

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