Depth-Profiling Study on Amorphous Indium–Gallium–Zinc Oxide Thin-Film Transistors by X-ray Photoelectron Spectroscopy

Iwamatsu, Shinnosuke; Takechi, Kazushige; Yahagi, Toru; Watanabe, Yoshihisa; Tanabe, Hiroshi; Kobayashi, Sadao

doi:10.7567/jjap.52.03bb03

Cited by 9 publications

(4 citation statements)

References 27 publications

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“…Figures 3(a)-(c) show the XPS spectra for In 3d, Ga 2p and Zn 2p for a-IGZO film. There is no obvious difference between these In, Ga, Zn XPS spectra and those in a previous report [32]. The O 1s spectrum distinguishes V o , which are the most important defects in IGZO films.…”

Section: Materials Analysiscontrasting

confidence: 39%

Trap-assisted photomultiplication in a-IGZO/p-Si heterojunction ultraviolet photodiodes

Huang

Hsiao

et al. 2020

Smart Mater. Struct.

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Many applications require a photodetector (PD) with a large gain to detect very low levels of ultraviolet (UV) light. However, a large gain is generally produced using an impact ionization process, which requires a very large applied voltage. This study demonstrates a photomultiplication (PM)-type UV PD with a simple structure that uses an a-IGZO/p-Si heterojunction. The device exhibits an external quantum efficiency (EQE) of 2565% under 325 nm illumination at a reverse bias of −5 V. The oxygen vacancy (Vo) state in a-IGZO is relaxed to a deep bandgap but is fully occupied by two electrons. Vo with doubly charged Vo 2+ or singly charged Vo + can be excited by UV light. This produces free electrons. There is a high EQE at low reverse-bias because trapped electrons are emitted from the Vo. The IGZO/Si heterojunction also has a high response speed (∼1 ms) in the self-powered mode because the built-in potential separates electron–hole pairs immediately. This study shows that an a-IGZO/p-Si heterojunction not only acts as a PM-type PD with a low driving voltage but also as a high-speed self-powered PD to reduce power consumption.

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Section: Materials Analysiscontrasting

confidence: 39%

Trap-assisted photomultiplication in a-IGZO/p-Si heterojunction ultraviolet photodiodes

Huang

Hsiao

et al. 2020

Smart Mater. Struct.

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“…Figure 2b depicts the XPS spectrum of In 3d 5/2 in the V Orich layer of high-In ITZO. It can be divided into two peaks, one from the oxide with the stoichiometric composition located near 444.8 eV and the other from the oxide state with oxygen deficiency located at 443.1 eV, 26 and Figure 2c depicts similar phenomena in the Sn 3d 5/2 spectrum. 27 These suggest that the back channel of ITZO shows a clear tendency of metallization, coupling well with its V O -rich state.…”

Section: Resultsmentioning

confidence: 92%

Impact of the Source/Drain Electrode Process on the Mobility-Threshold Trade-Off for InSnZnO Thin-Film Transistors

Yang

Gao

et al. 2023

ACS Appl. Electron. Mater.

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In this work, the source/drain (S/D) electrode process is considered to have a great impact on the mobility (μ FE )− threshold (V th ) trade-off for high-mobility amorphous oxide semiconductor (AOS) thin-film transistors. High-mobility AOS materials have worse oxygen-fixation ability compared to InGaZnO. In this work, we show that this is the case for the Mo S/D electrode process on InSnZnO channels and has a great impact on the mobility-threshold trade-off. Oxygen vacancy gradients are observed in the depth profile X-ray photoelectron spectroscopy analysis on InSnZnO after Mo S/D deposition and show a bigger change in oxygen vacancies (V O ) between the surface and inner layers and thicker compared to InGaZnO. This leads to an obvious negative shift in V th or even no switching characteristic. Postprocessing such as oxygen-plasma treatment can make V th positive but degrade the μ FE . In situ replenishing oxygen via adopting ITO S/D electrodes deposited in an oxygen-containing atmosphere facilitates the achievement of excellent overall electrical characteristics, with μ FE up to 87.1 cm 2 /Vs, V th ∼ −0.64 V, and I on /I off ∼ 2.3 × 10 8 .

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“…Up to now, mainly three types of oxide TFTs have been researched and developed. The first is a back channel etch (BCE)-type TFT that applies a process similar to that of the amorphous silicon (a-Si) TFT and etches source and drain (S/D) metal to form a back channel (6,9). The second is an etch stop layer (ESL)-type TFT that is protected by an ESL in advance to prevent the back-channel interface from being exposed to etching (7,10).…”

Section: Introductionmentioning

confidence: 99%

(Invited) Hot Carrier Phenomena in Oxide Thin-Film Transistors

Tanaka¹,

Fujii

Miyanaga

et al. 2020

ECS Trans.

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We observed hot carrier-induced photon emissions in oxide TFTs with structures of BCE-type and TG-type for the first time in addition to ESL-type. In this paper, the effects of these TFT structures on the hot carrier phenomena are described using TFT characteristics, photon-emission analysis, and TCAD simulation. We observed the degradation of TFT characteristics in BCE-type and TG-type, which was similar to that in Si-based devices, along with the photon emission. In contrast, for the ESL-type, we found the behavior depending on the drain–ESL overlap length. When this overlap length was under 1µm, photon emission and no significant shift of TFT characteristics were observed; however, when it was 3µm, no photon emission and a significant shift of TFT characteristics were observed. Based on the potential distributions near the drain obtained by the TCAD simulation, we propose the degradation mechanism of ESL-type depending on the drain–ESL overlap length.

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Depth-Profiling Study on Amorphous Indium–Gallium–Zinc Oxide Thin-Film Transistors by X-ray Photoelectron Spectroscopy

Cited by 9 publications

References 27 publications

Trap-assisted photomultiplication in a-IGZO/p-Si heterojunction ultraviolet photodiodes

Trap-assisted photomultiplication in a-IGZO/p-Si heterojunction ultraviolet photodiodes

Impact of the Source/Drain Electrode Process on the Mobility-Threshold Trade-Off for InSnZnO Thin-Film Transistors

(Invited) Hot Carrier Phenomena in Oxide Thin-Film Transistors

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