Amorphous Silicon Thin-Film Transistors: Operation, Modelling and Applications

141 Pages·2023·3.136 MB·English

by  Zoubeida Hafdi

Synthesis Lectures on
Engineering, Science, and Technology
Zoubeida Hafdi
Amorphous Silicon
Thin-Film Transistors
Operation, Modelling and Applications
Synthesis Lectures on Engineering, Science,
and Technology
The focus of this series is general topics, and applications about, and for, engineers
and scientists on a wide array of applications, methods and advances. Most titles cover
subjects such as professional development, education, and study skills, as well as basic
introductory undergraduate material and other topics appropriate for a broader and less
technical audience.
Zoubeida Hafdi
Amorphous Silicon
Thin-Film Transistors
Operation, Modelling and Applications
Zoubeida Hafdi
Département du Tronc Commun en Sciences et
Technologie, Faculty of Technology
Batna 2 University
Batna, Algeria
ISSN 2690-0300 ISSN 2690-0327 (electronic)
Synthesis Lectures on Engineering, Science, and Technology
ISBN 978-3-031-24792-7 ISBN 978-3-031-24793-4 (eBook)
https://doi.org/10.1007/978-3-031-24793-4
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To the memory of my Parents
To Noureddine Nabti;
inspiring husband, good friend and source of
perpetual patience
Preface
Amorphous silicon material has imposed itself as a basic part of a mature technology
for several years to date. Amorphous silicon technology facilitated to the highest degree
the control of amorphous silicon-based thin-film transistor electronic characteristics. This
improvement is due to the fabrication reproducibility and uniformity over large area of
amorphous silicon components and display backplanes which acted in favor of the expand-
ing of this technology. This is also owed to the low-cost fabrication and the scalability to
larger-sized substrates. At the device level and in parallel to manufacturing issues, models
are to be developed and implementation means are to be thought in such a way that the
transistor can overcome the challenges associated to the new and nontraditional future
applications, namely those related to flexible electronics.
The book fits into this context. It is the essence of several years of work on thin-
film transistors based on amorphous silicon from the material level to the circuit one.
Effort was focused on basics for physical fundamentals, modeling and simulations as a
bridge to practical applications that may extend beyond active matrices and the associated
peripheral circuits. It tries, as far as possible, to help rapidly building ideas from targeted
concepts by an emphasis on acquisition of basic, general and technical knowledge. It also
recalls modeling and simulation as important concerns for integrated circuit design. It
exposes at what extent simulation may reveal the implemented model accuracy and its
aptitude to predict devices and circuits behavior before the manufacturing phase. Besides,
some optimization design practices and strategies to build reliable circuits are highlighted.
The book is at the same time introductory, undergraduate, graduate and continuing
education textbook since it provides information at many levels beginning by basics
and fundamentals at the material level to advanced information for device and circuit
design. It has the objective to give the basic principles that the reader needs to know
about amorphous silicon material and amorphous silicon-based transistors. It is appro-
priate for undergraduate and graduate students, circuit simulators developers, integrated
circuits designers and manufacturers, as well as everyone engaged in work on large area
integrated circuit technologies, photovoltaics and low-cost applications and would like to
have introductory concepts in amorphous silicon technology.
vii
viii Preface
The required background falls under the theme of component and integrated cir-
cuit physics, design and fabrication. This involves knowledge on advances and design
of application-specific circuits, semiconductor technology and characterization, and
design aids for the control of the design flows for amorphous silicon-based circuit
implementation.
Along with principles, the proposed book is thought to be a vehicle of simplicity as
it enhances simple and expressive modeling of a-Si:H TFTs. Effort is made to make the
content clear and simple enough to be understood by the reader. Model fundamentals are
first detailed to allow accurate and fast device simulation and characterization, and then,
some basic a-Si:H TFT applications for digital and high-voltage generation circuit design
are covered.
Constantine, Algeria Zoubeida Hafdi
2022
Acknowledgements
The author is very thankful to the following organizations for their permission obtained
for material she has previously published:
Organization Journals, Proceedings…
Elsevier B.V. Open access Physics Procedia
IDOSI Publications World Applied Sciences Journal
Institute of Electrical and Electronics IEEE Proceedings
Engineers (IEEE)
The Japan Society of Applied Physics Japanese Journal of Applied Physics
The Society of Digital Information and International Conference on Digital Information:
Wireless Communications (SDIWC) Processing, Electronics, and Wireless
Communications, Proc.
The author is also grateful to Doctor Nelva Nely Almanza Ortega from the Tecnológico
Nacional de México/IT de Tlalnepantla for her constant support.
Constantine, Algeria Zoubeida Hafdi
2022 [email protected]
ix
Contents
1 Introduction ......................................................... 1
References ........................................................... 8
2 Hydrogenated Amorphous Silicon Thin-Film Transistors ................ 11
2.1 Introduction .................................................... 11
2.2 Amorphous Silicon and a-Si:H TFTs .............................. 12
2.3 Silicon Nitride .................................................. 14
2.4 Thin-Film Transistor Structures ................................... 14
2.5 Thin-Film Transistor Materials .................................... 15
2.6 a-Si:H TFTs Performance Requirements ........................... 16
2.7 a-Si:H TFT Operation ........................................... 17
2.7.1 Subthreshold or Weak Accumulation Regime ................. 18
2.7.2 Above Threshold or High Accumulation Regime ............. 18
2.7.3 Transitional Regime ....................................... 18
2.7.4 Crystalline-Like Regime ................................... 19
References ........................................................... 19
3 Amorphous Silicon-Based MIS Structure ............................... 23
3.1 Introduction .................................................... 23
3.2 Density of States in the Amorphous Silicon ........................ 24
3.3 Band Diagram .................................................. 25
3.4 Charge Densities ................................................ 26
3.4.1 Density of Free Electrons .................................. 26
3.4.2 Charge Density in the Deep Localized States ................. 26
3.4.3 Charge Density in Tail Localized States ..................... 28
3.5 MIS Structure DC Analysis ...................................... 29
3.5.1 Assumptions and Calculation Principle ...................... 29
3.5.2 Poisson Equation ......................................... 29
3.5.3 Potential Equilibrium ...................................... 30
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