Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics

Divine Khan Ngwashi; Shashi Paul; Anjana Devi; Richard Barrie Michael Cross

doi:doi:10.11648/j.am.20180704.16

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Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics

Divine Khan Ngwashi, Shashi Paul, Anjana Devi, Richard Barrie Michael Cross

Published in Advances in Materials (Volume 7, Issue 4)

Received: 21 November 2018 Accepted: 13 December 2018 Published: 10 January 2019

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Abstract

This work investigates the performance and gate bias stress instability of ZnO-based thin film transistors (ZnO-TFTs) incorporating amorphous gadolinium oxide, a high-k dielectric material. ZnO thin films produced via radio frequency (RF) reactive magnetron sputtering were used as channel layers. The source/drain electrodes were achieved by the thermal evaporation of aluminium on a bottom gate inverted staggered ZnO TFT structure. Gadolinium oxide (Gd₂O₃) deposited by metal-organic chemical vapour deposition (MOCVD) served as the gate dielectric. The electrical characterisation of the ZnO-TFTs produced showed improvement in performance and stability in comparison to thermally-grown SiO₂-based ZnO TFTs fabricated under the same conditions. The effective channel mobility, on-off current ratio and subthreshold swing of the TFTs incorporating Gd₂O₃ dielectric were found to be 33.5 cm² V^-1s^-1, 10⁷, and 2.4 V/dec respectively when produced. The electrical characterisation of the same devices produced with SiO2 dielectrics exhibited effective mobility, on-off current ratio and subthreshold swing of 7.0 cm2 V^-1s^-1, 10⁶ and 1.4 V/dec respectively. It is worth noting that, the ZnO active layer was sputtered under room temperature with no intentional heating and post-deposition annealing treatment. On application of gate bias stressing on these thin film transistors, it was observed that threshold voltage instability increased with stress period in all device types. Transistors incorporating Gd₂O₃ however, were found to exhibit lesser threshold voltage related instability with regards to gate bias stressing in comparison to similar devices incorporating SiO₂ as gate dielectric. It was also observed that the effective mobility in both devices tend to stabilize with prolonged gate bias application. In this work, it is demonstrated that Gd₂O₃ dielectric is a potential alternative to SiO₂ for the fabrication of ZnO TFTs with improved performance and electrical stability under prolonged use.

Published in	Advances in Materials (Volume 7, Issue 4)
DOI	10.11648/j.am.20180704.16
Page(s)	137-143
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2019. Published by Science Publishing Group

Keywords

Zinc Oxide, Thin Film Transistors, Gd2O3, Performance, Gate Bias Stress Instability, High-K Dielectrics, Magnetron Sputtering, TFT

References

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APA Style

Divine Khan Ngwashi, Shashi Paul, Anjana Devi, Richard Barrie Michael Cross. (2019). Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics. Advances in Materials, 7(4), 137-143. https://doi.org/10.11648/j.am.20180704.16

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ACS Style

Divine Khan Ngwashi; Shashi Paul; Anjana Devi; Richard Barrie Michael Cross. Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics. Adv. Mater. 2019, 7(4), 137-143. doi: 10.11648/j.am.20180704.16

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AMA Style

Divine Khan Ngwashi, Shashi Paul, Anjana Devi, Richard Barrie Michael Cross. Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics. Adv Mater. 2019;7(4):137-143. doi: 10.11648/j.am.20180704.16

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@article{10.11648/j.am.20180704.16,
  author = {Divine Khan Ngwashi and Shashi Paul and Anjana Devi and Richard Barrie Michael Cross},
  title = {Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics},
  journal = {Advances in Materials},
  volume = {7},
  number = {4},
  pages = {137-143},
  doi = {10.11648/j.am.20180704.16},
  url = {https://doi.org/10.11648/j.am.20180704.16},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.am.20180704.16},
  abstract = {This work investigates the performance and gate bias stress instability of ZnO-based thin film transistors (ZnO-TFTs) incorporating amorphous gadolinium oxide, a high-k dielectric material. ZnO thin films produced via radio frequency (RF) reactive magnetron sputtering were used as channel layers. The source/drain electrodes were achieved by the thermal evaporation of aluminium on a bottom gate inverted staggered ZnO TFT structure. Gadolinium oxide (Gd2O3) deposited by metal-organic chemical vapour deposition (MOCVD) served as the gate dielectric. The electrical characterisation of the ZnO-TFTs produced showed improvement in performance and stability in comparison to thermally-grown SiO2-based ZnO TFTs fabricated under the same conditions. The effective channel mobility, on-off current ratio and subthreshold swing of the TFTs incorporating Gd2O3 dielectric were found to be 33.5 cm2 V-1s-1, 107, and 2.4 V/dec respectively when produced. The electrical characterisation of the same devices produced with SiO2 dielectrics exhibited effective mobility, on-off current ratio and subthreshold swing of 7.0 cm2 V-1s-1, 106 and 1.4 V/dec respectively. It is worth noting that, the ZnO active layer was sputtered under room temperature with no intentional heating and post-deposition annealing treatment. On application of gate bias stressing on these thin film transistors, it was observed that threshold voltage instability increased with stress period in all device types. Transistors incorporating Gd2O3 however, were found to exhibit lesser threshold voltage related instability with regards to gate bias stressing in comparison to similar devices incorporating SiO2 as gate dielectric. It was also observed that the effective mobility in both devices tend to stabilize with prolonged gate bias application. In this work, it is demonstrated that Gd2O3 dielectric is a potential alternative to SiO2 for the fabrication of ZnO TFTs with improved performance and electrical stability under prolonged use.},
 year = {2019}
}

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TY  - JOUR
T1  - Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics
AU  - Divine Khan Ngwashi
AU  - Shashi Paul
AU  - Anjana Devi
AU  - Richard Barrie Michael Cross
Y1  - 2019/01/10
PY  - 2019
N1  - https://doi.org/10.11648/j.am.20180704.16
DO  - 10.11648/j.am.20180704.16
T2  - Advances in Materials
JF  - Advances in Materials
JO  - Advances in Materials
SP  - 137
EP  - 143
PB  - Science Publishing Group
SN  - 2327-252X
UR  - https://doi.org/10.11648/j.am.20180704.16
AB  - This work investigates the performance and gate bias stress instability of ZnO-based thin film transistors (ZnO-TFTs) incorporating amorphous gadolinium oxide, a high-k dielectric material. ZnO thin films produced via radio frequency (RF) reactive magnetron sputtering were used as channel layers. The source/drain electrodes were achieved by the thermal evaporation of aluminium on a bottom gate inverted staggered ZnO TFT structure. Gadolinium oxide (Gd2O3) deposited by metal-organic chemical vapour deposition (MOCVD) served as the gate dielectric. The electrical characterisation of the ZnO-TFTs produced showed improvement in performance and stability in comparison to thermally-grown SiO2-based ZnO TFTs fabricated under the same conditions. The effective channel mobility, on-off current ratio and subthreshold swing of the TFTs incorporating Gd2O3 dielectric were found to be 33.5 cm2 V-1s-1, 107, and 2.4 V/dec respectively when produced. The electrical characterisation of the same devices produced with SiO2 dielectrics exhibited effective mobility, on-off current ratio and subthreshold swing of 7.0 cm2 V-1s-1, 106 and 1.4 V/dec respectively. It is worth noting that, the ZnO active layer was sputtered under room temperature with no intentional heating and post-deposition annealing treatment. On application of gate bias stressing on these thin film transistors, it was observed that threshold voltage instability increased with stress period in all device types. Transistors incorporating Gd2O3 however, were found to exhibit lesser threshold voltage related instability with regards to gate bias stressing in comparison to similar devices incorporating SiO2 as gate dielectric. It was also observed that the effective mobility in both devices tend to stabilize with prolonged gate bias application. In this work, it is demonstrated that Gd2O3 dielectric is a potential alternative to SiO2 for the fabrication of ZnO TFTs with improved performance and electrical stability under prolonged use.
VL  - 7
IS  - 4
ER  -

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Author Information

Divine Khan Ngwashi

Department of Electrical and Electronics Engineering, University of Buea, Buea, Cameroon
Shashi Paul

Emerging Technologies Research Centre, De Montfort University, Leicester, United Kingdom
Anjana Devi

Inorganic Chemistry II, Ruhr-University, Bochum, Germany
Richard Barrie Michael Cross

Emerging Technologies Research Centre, De Montfort University, Leicester, United Kingdom

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APA Style

Divine Khan Ngwashi, Shashi Paul, Anjana Devi, Richard Barrie Michael Cross. (2019). Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics. Advances in Materials, 7(4), 137-143. https://doi.org/10.11648/j.am.20180704.16

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ACS Style

Divine Khan Ngwashi; Shashi Paul; Anjana Devi; Richard Barrie Michael Cross. Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics. Adv. Mater. 2019, 7(4), 137-143. doi: 10.11648/j.am.20180704.16

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AMA Style

Divine Khan Ngwashi, Shashi Paul, Anjana Devi, Richard Barrie Michael Cross. Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics. Adv Mater. 2019;7(4):137-143. doi: 10.11648/j.am.20180704.16

Copy | Download

@article{10.11648/j.am.20180704.16,
  author = {Divine Khan Ngwashi and Shashi Paul and Anjana Devi and Richard Barrie Michael Cross},
  title = {Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics},
  journal = {Advances in Materials},
  volume = {7},
  number = {4},
  pages = {137-143},
  doi = {10.11648/j.am.20180704.16},
  url = {https://doi.org/10.11648/j.am.20180704.16},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.am.20180704.16},
  abstract = {This work investigates the performance and gate bias stress instability of ZnO-based thin film transistors (ZnO-TFTs) incorporating amorphous gadolinium oxide, a high-k dielectric material. ZnO thin films produced via radio frequency (RF) reactive magnetron sputtering were used as channel layers. The source/drain electrodes were achieved by the thermal evaporation of aluminium on a bottom gate inverted staggered ZnO TFT structure. Gadolinium oxide (Gd2O3) deposited by metal-organic chemical vapour deposition (MOCVD) served as the gate dielectric. The electrical characterisation of the ZnO-TFTs produced showed improvement in performance and stability in comparison to thermally-grown SiO2-based ZnO TFTs fabricated under the same conditions. The effective channel mobility, on-off current ratio and subthreshold swing of the TFTs incorporating Gd2O3 dielectric were found to be 33.5 cm2 V-1s-1, 107, and 2.4 V/dec respectively when produced. The electrical characterisation of the same devices produced with SiO2 dielectrics exhibited effective mobility, on-off current ratio and subthreshold swing of 7.0 cm2 V-1s-1, 106 and 1.4 V/dec respectively. It is worth noting that, the ZnO active layer was sputtered under room temperature with no intentional heating and post-deposition annealing treatment. On application of gate bias stressing on these thin film transistors, it was observed that threshold voltage instability increased with stress period in all device types. Transistors incorporating Gd2O3 however, were found to exhibit lesser threshold voltage related instability with regards to gate bias stressing in comparison to similar devices incorporating SiO2 as gate dielectric. It was also observed that the effective mobility in both devices tend to stabilize with prolonged gate bias application. In this work, it is demonstrated that Gd2O3 dielectric is a potential alternative to SiO2 for the fabrication of ZnO TFTs with improved performance and electrical stability under prolonged use.},
 year = {2019}
}

Copy | Download

TY  - JOUR
T1  - Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics
AU  - Divine Khan Ngwashi
AU  - Shashi Paul
AU  - Anjana Devi
AU  - Richard Barrie Michael Cross
Y1  - 2019/01/10
PY  - 2019
N1  - https://doi.org/10.11648/j.am.20180704.16
DO  - 10.11648/j.am.20180704.16
T2  - Advances in Materials
JF  - Advances in Materials
JO  - Advances in Materials
SP  - 137
EP  - 143
PB  - Science Publishing Group
SN  - 2327-252X
UR  - https://doi.org/10.11648/j.am.20180704.16
AB  - This work investigates the performance and gate bias stress instability of ZnO-based thin film transistors (ZnO-TFTs) incorporating amorphous gadolinium oxide, a high-k dielectric material. ZnO thin films produced via radio frequency (RF) reactive magnetron sputtering were used as channel layers. The source/drain electrodes were achieved by the thermal evaporation of aluminium on a bottom gate inverted staggered ZnO TFT structure. Gadolinium oxide (Gd2O3) deposited by metal-organic chemical vapour deposition (MOCVD) served as the gate dielectric. The electrical characterisation of the ZnO-TFTs produced showed improvement in performance and stability in comparison to thermally-grown SiO2-based ZnO TFTs fabricated under the same conditions. The effective channel mobility, on-off current ratio and subthreshold swing of the TFTs incorporating Gd2O3 dielectric were found to be 33.5 cm2 V-1s-1, 107, and 2.4 V/dec respectively when produced. The electrical characterisation of the same devices produced with SiO2 dielectrics exhibited effective mobility, on-off current ratio and subthreshold swing of 7.0 cm2 V-1s-1, 106 and 1.4 V/dec respectively. It is worth noting that, the ZnO active layer was sputtered under room temperature with no intentional heating and post-deposition annealing treatment. On application of gate bias stressing on these thin film transistors, it was observed that threshold voltage instability increased with stress period in all device types. Transistors incorporating Gd2O3 however, were found to exhibit lesser threshold voltage related instability with regards to gate bias stressing in comparison to similar devices incorporating SiO2 as gate dielectric. It was also observed that the effective mobility in both devices tend to stabilize with prolonged gate bias application. In this work, it is demonstrated that Gd2O3 dielectric is a potential alternative to SiO2 for the fabrication of ZnO TFTs with improved performance and electrical stability under prolonged use.
VL  - 7
IS  - 4
ER  -

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