Metal Oxide Semiconductors (eBook)

Synthesis, Properties, and Devices

Zhigang Zang, Wensi Cai, Yong Zhou (Autoren)

eBook Download: EPUB

2023 | 1. Auflage
288 Seiten
Wiley-VCH (Verlag)
978-3-527-84256-8 (ISBN)

Infos

Metal Oxide Semiconductors

Up-to-date resource highlighting highlights emerging applications of metal oxide semiconductors in various areas and current challenges and directions in commercialization

Metal Oxide Semiconductors provides a current understanding of oxide semiconductors, covering fundamentals, synthesizing methods, and applications in diodes, thin-film transistors, gas sensors, solar cells, and more. The text presents state-of-the-art information along with fundamental prerequisites for understanding and discusses the current challenges in pursuing commercialization and future directions of this field.

Despite rapid advancements in the materials science and device physics of oxide semiconductors over the past decade, the understanding of science and technology in this field remains incomplete due to its relatively short research history; this book aims to bridge the gap between the rapidly advancing research progress in this field and the demand for relevant materials and devices by researchers, engineers, and students.

Written by three highly qualified authors, Metal Oxide Semiconductors discusses sample topics such as:

• Fabrication techniques and principles, covering vacuum-based methods, including sputtering, atomic layer deposition and evaporation, and solution-based methods
• Fundamentals, progresses, and potentials of p-n heterojunction diodes, Schottky diodes, metal-insulator-semiconductor diodes, and self-switching diodes
• Applications in thin-film transistors, detailing the current progresses and challenges towards commercialization for n-type TFTs, p-type TFTs, and circuits
• Detailed discussions on the working mechanisms and representative devices of oxide-based gas sensors, pressure sensors, and PH sensors
• Applications in optoelectronics, both in solar cells and ultraviolet photodetectors, covering their parameters, materials, and performance
• Memory applications, including resistive random-access memory, transistor-structured memory devices, transistor-structured artificial synapse, and optical memory transistors

A comprehensive monograph covering all aspects of oxide semiconductors, Metal Oxide Semiconductors is an essential resource for materials scientists, electronics engineers, semiconductor physicists, and professionals in the semiconductor and sensor industries who wish to understand all modern developments that have been made in the field.

Prof. Zhigang Zang received his PhD degree from Kyushu University in 2011. He joined School of Optoelectronic Engineering, Chongqing University as a professor since 2014.

Dr. Wensi Cai received her PhD degree from University of Manchester in 2019. She joined Chongqing University as a postdoctoral researcher in 2020.

Prof. Yong Zhou, PhD, joined the School of Optoelectronic Engineering of Chongqing University in June 2015.

Autor

Prof. Zhigang Zang received his PhD degree from Kyushu University in 2011. He joined School of Optoelectronic Engineering, Chongqing University as a professor since 2014. His research interests mainly focus on the synthesis of II-VI, III-V semiconductor materials and their applications in solar cells, photodetectors and light emitting diodes. He has published more than 150 papers and has been selected as national important talent plan. Dr. Wensi Cai received her PhD degree from University of Manchester in 2019. She joined Chongqing University as a postdoc researcher since 2020. Her research interests mainly focus on oxide semiconductor- and perovskite-based electron devices. Zhou Yong, Ph.D., associate professor, joined the School of Optoelectronic Engineering of Chongqing University in June 2015. At present, the main research direction is to study the preparation of molecular gas sensors for monitoring of the environment, human breathing gas, national defense and anti-terrorism, public security, and industrial production.

Inhalt

1 Metal Oxide Semiconductors: State-of-the-Art and New Challenges
2 Fabrication Techniques and Principles
3 Metal Oxide Semiconductors for Diodes
4 Metal Oxide Semiconductors for Transistors
5 Metal Oxide Semiconductors for Sensors
6 Metal Oxide Semiconductors for Solar Cells
7 Metal Oxide Semiconductors for Ultraviolet Photodetectors
8 Metal Oxide Semiconductors for Memory Applications

Textauszug

1
Metal Oxide Semiconductors: State-of-the-Art and New Challenges

1.1 Introduction

Metal oxide semiconductors (MOS) are abundant materials found in the Earth's crust and are commonly used in traditional ceramics. However, they differ significantly from conventional inorganic counterparts like silicon and III–V compounds in various aspects. These distinctions encompass materials design concepts, electronic structure, charge transport mechanisms, defect states, thin-film processing, and optoelectronic properties. As a result, oxide semiconductors enable the realization of both established and innovative functionalities [1].

In comparison to inorganic semiconductors, oxide semiconductors possess unique characteristics. These include exceptional carrier mobilities even in the amorphous state, resilience against mechanical stress, compatibility with organic dielectric and photoactive materials, and high optical transparency. These properties make oxide semiconductors particularly appealing for various applications.

In recent decades, MOS have garnered significant attention in various research fields, including optoelectronics, thin-film transistors (TFTs), photocatalysts, gas sensors, solar cells, and memristors [1–14], as shown in Figure 1.1. MOS can be categorized into two types based on their conductivity: n-type, where electrons are the majority carriers, and p-type, where holes are the majority carriers. These semiconducting properties arise from factors such as doped aliovalent cations or oxygen nonstoichiometry [15, 16]. Among the n-type MOS, ZnO, SnO2, TiO2, In2O3, and Ga2O3 are widely studied concerning synthesis, characterization, and applications [17–21]. As for the p-type MOS, research efforts primarily focus on CuxO (CuO and Cu2O), SnO, and NiOx [22–24].

1.2 n-Type Metal Oxide Semiconductors

1.2.1 ZnO

Zinc oxide (ZnO), as an n-type semiconductor, has sparked significant research interest due to its distinctive physical and chemical properties [25–27]. In the field of materials science, ZnO is classified as a II–VI compound semiconductor, possessing a covalence level between ionic and covalent semiconductors. Its attributes, such as a direct wide bandgap (Eg ∼ 3.3 eV at 300 K), large free exciton binding energy (60 meV), and high thermal and mechanical stability at room temperature, make ZnO a promising candidate for various applications in electronic devices, optoelectronics, gas sensors, and laser technology [28, 29]. Additionally, ZnO can be utilized as an energy collector due to its piezo- and pyroelectric properties, as well as a photocatalyst for hydrogen production [30–32].

Figure 1.1 Applications of metal oxide semiconductors.

Source: Reprinted with permission from Refs. [9–14]. Copyright 2015 American Chemical Society, 2016 American Chemical Society, 2020 American Chemical Society, 2020 The Royal Society of Chemistry.

The crystal structure of ZnO can be classified into three types: wurtzite (B4), zinc blende (B3), and rocksalt (B1), as shown in Figure 1.2. Thereinto, wurtzite is the most stable thermodynamic phase under ambient conditions. Wurtzite ZnO possesses a hexagonal structure (space group C6mc) with lattice parameters a = 0.3296 nm and c = 0.52065 nm. The structure of ZnO can be simply described as a number of alternating planes composed of tetrahedrally coordinated O2− and Zn2+ ions, stacked alternately along the c-axis. The tetrahedral coordination in ZnO results in noncentral symmetric structures and consequently piezoelectricity and pyroelectricity [33].

Figure 1.2 Stick and ball representation of ZnO crystal structures: (a) cubic rocksalt (B1), (b) cubic zinc blende (B3), and (c) hexagonal wurzite (B4). The gray and red spheres denote Zn and O atoms, respectively.

Figure 1.3 Bulk structures of SnO2 polymorphs (gray and red colors represent Sn and O atoms, respectively). (a) Rutile (P42/mnm) and CaCl2-type (Pnnm), (b) R-PbO2-type (Pbcn), (c) pyrite-type (Pa), (d) ZrO2-type (Pbca), (e) fluorite-type (Fmhm), and (f) cotunnite-type (Pnam).

Source: Reproduced from Gracia et al. [40]/with permission of American Chemical Society.

1.2.2 SnO2

SnO2 is also a wide-bandgap (∼3.6 eV) n-type semiconductor, belongs to the group-IV compounds, and exhibits remarkable transparency and conductivity simultaneously [20, 34, 35]. The unique chemical, electronic, and optical properties of SnO2 have led to extensive research on its applications in various devices, including solar cells [36], catalytic materials [37], and gas sensors [38]. Additionally, SnO2 serves as a distinctive transparent metal oxide and finds wide-ranging applications as transparent conducting oxide electrodes in optoelectronic devices. This is due to its excellent chemical and thermal stabilities in atmospheric environments, as well as its high optical transmission properties [39].

SnO2 possesses several polymorphs including rutile-type (P42/mnm), CaCl2-type (Pnnm), a-PbO2-type (Pbcn), pyrite-type (Pa), ZrO2-type orthorhombic phase I (Pbca), fluorite-type (Fmm), and cotunnite-type orthorhombic phase II (Pnam) with ninefold coordination, as shown in Figure 1.3. All these structures are sequentially obtained when the most commonly available and stable rutile phase is subjected to a high mechanical pressure [40].

1.2.3 In2O3

Another widely studied n-type semiconductor is indium oxide (In2O3), which has a bandgap ranging from 3.5 to 3.7 eV. It finds numerous applications in electronic and optoelectronic fields such as solar cells, gas sensors based on TFTs, and Schottky contacts and diodes [21, 41]. In2O3 can exist in two well-established crystal structures: body-centered cubic (bcc) and rhombohedral (rh), as depicted in Figure 1.4 [42]. The phase of In2O3 thermodynamically stable under ambient conditions adopts the body-centered cubic bixbyite structure, with the space group Ia (#206) and a lattice constant of 10.118 Å. The rhombohedral structure is stabilized under high-pressure conditions. The rhombohedral cell belongs to the Rc space group with lattice constants a = 5.478 Å and c = 14.51 Å. There are six formula units per hexagonal cell, and the volume per formula of 62.85 Å3 for the rh phase is much smaller than the value of 64.72 Å3 for the ambient bcc phase.

Figure 1.4 Ball and stick representations of crystal structures of bcc-In2O3 (a, b) and rh-In2O3 (c, d). In atoms are pale pink, and O atoms are dark red. The viewing directions and the in-plane orientation are indicated in the figure.

Source: Reproduced from Zhang et al. [42]/with permission of American Chemical Society.

1.2.4 TiO2

As a member of transition metal oxides, TiO2 is a well-known n-type semiconductor [43–46]. It exhibits excellent electronic and optical properties, making it highly suitable for various applications in the fields of gas sensors [47], solar cells [48], and photocatalysis [49]. In its natural form, TiO2 exists in three different phase structures, namely anatase (tetragonal), brookite (orthorhombic), and rutile (tetragonal), as illustrated in Figure 1.5. These phases have energy bandgaps of 3.2 eV (anatase), 3.02 eV (brookite), and 2.96 eV (rutile) [50, 51]. Among these phases, anatase and rutile are widely applied due to their superior stability, while rutile TiO2, with a tetragonal structure containing six atoms per unit cell, exhibits a slight distortion in the TiO6 octahedron [52]. Anatase TiO2 also possesses a tetragonal structure, but with a slightly larger distortion of the TiO6 octahedron. In general, rutile TiO2 is more thermodynamically stable than anatase under typical temperature and pressure conditions.

Figure 1.5 Structure of anatase, rutile, and brookie TiO2.

Source: Reproduced from Macwan et al. [51]/with permission of American Chemical Society.

1.2.5 Ga2O3

Ga2O3 is an emerging ultra-wide bandgap semiconductor with a bandgap of 4.8 eV. This unique property enables Ga2O3 to simultaneously achieve high breakdown voltage and low on-resistance, making it highly promising for both direct current (DC) and radiofrequency (RF) applications [53, 54]. As a result, Ga2O3 offers exciting prospects in various fields such as electronics (high-power devices, field-effect transistors) [55], optoelectronics (solar cells, solar-blind ultraviolet photodetectors) [56–58], and...

Produkt-Details

• Erscheint lt. Verlag: 29.11.2023
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Chemie
• Schlagworte: Components & Devices • Electrical & Electronics Engineering • Electronic materials • Elektronische Materialien • Elektrotechnik u. Elektronik • Halbleiter • Halbleiterphysik • Komponenten u. Bauelemente • Materials Science • Materialwissenschaften • Metalloxide • Physics • Physik • Semiconductor physics
• ISBN-10: 3-527-84256-X / 352784256X
• ISBN-13: 978-3-527-84256-8 / 9783527842568