New Advances in Thin-Film Transistor

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Thin Films".

Deadline for manuscript submissions: closed (28 February 2022) | Viewed by 26961

Special Issue Editor

National Institute for Materials Science
Interests: semiconductor phyiscs; surface and interface physics; semiconductor devices; transistors; logic circuits; diodes; capacitors; diamond; ZnO; photoelectron spectroscopy

Special Issue Information

Dear Colleagues,

As you know, the thin-film transistor (TFT) is a basic electronic device. It is a special type of metal–oxide–semiconductor field-effect transistor. TFTs have attracted a lot of attention due to their applications in the fields of liquid crystal displays, sensors, biomarkers, flexible integrated circuits, etc. In order to fabricate high-performance TFTs and expand their new applications, many researchers have focused on the development of semiconductor materials, dielectric insulators, and Ohmic contacts. In the last few years, significant progress in TFTs has been achieved. It would thus be of great value to gather the outcomes of recent research on them. This Special Issue focuces on TFTs and their novel applications.

In particular, the topic of interest includes but is not limited to

  • Thin-film transistors (TFTs);
  • Metal–oxide–semiconductor field-effect transistors (MOSFETs);
  • Semiconductors for TFTs and MOSFETs;
  • Dielectrics for TFTs and MOSFETs;
  • Ohmic contracts for TFTs and MOSFETs;
  • Dielectric/semiconductor interfaces;
  • Ohmic/semiconductor interfaces;
  • Novel applications for TFTs.

Dr. Jiangwei Liu
Guest Editor

Manuscript Submission Information

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Published Papers (9 papers)

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Research

12 pages, 2728 KiB  
Article
Electrical and Hysteresis Characteristics of Top-Gate InGaZnO Thin-Film Transistors with Oxygen Plasma Treatment Prior to TEOS Oxide Gate Dielectrics
by Tsung-Cheng Tien, Tsung-Eong Hsieh, Yih-Shing Lee, Yu-Hsin Wang and Ming-Ling Lee
Coatings 2022, 12(3), 383; https://doi.org/10.3390/coatings12030383 - 14 Mar 2022
Cited by 1 | Viewed by 2337
Abstract
We report the impact of oxygen (O2) plasma time on an amorphous indium–gallium–zinc oxide (a-IGZO) thin-film surface that was carried out before TEOS deposition in order to optimize the performance of thin-film transistors (TFTs). TheO2 plasma time of 60 s [...] Read more.
We report the impact of oxygen (O2) plasma time on an amorphous indium–gallium–zinc oxide (a-IGZO) thin-film surface that was carried out before TEOS deposition in order to optimize the performance of thin-film transistors (TFTs). TheO2 plasma time of 60 s possessed the largest on/off current ratio of >108, with a field-effect mobility (µFE) of 8.14 cm2 V−1 s−1, and the lowest subthreshold swing (S.S.) of 0.395 V/decade, with a threshold voltage (Vth) of −0.14 V. However, increases in Ioff and S.S. and decreases in the µFE were observed for the longer O2 plasma time of 120 s. As the O2 plasma time increased, the reduction in the carrier concentration in the IGZO channel layer may have resulted in an increase in Vth for the IGZO TFT devices. With an increase in the O2 plasma time, the surface roughness of the IGZO channel layer was increased, the carbon content in the TEOS oxide film was reduced, and the film stoichiometry was improved. The SIMS depth profile results showed that the O/Si ratio of TEOS oxide for the sample with the O2 plasma time of 60 s was 2.64, and its IGZO TFT device had the best electrical characteristics. In addition, in comparison to the IGZO TFT device without O2 annealing, larger clockwise hysteresis in the transfer characteristics revealed that a greater number of electrons were trapped at the interface between TEOS oxide and the a-IGZO channel layer. However, hysteresis curves of the O2-annealed IGZO TFTs with various O2 plasma times were greatly reduced, meaning that the electron traps were reduced by O2 annealing. Full article
(This article belongs to the Special Issue New Advances in Thin-Film Transistor)
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11 pages, 6955 KiB  
Article
Effects of Ambience on Thermal-Diffusion Type Ga-doping Process for ZnO Nanoparticles
by Md Maruful Islam, Toshiyuki Yoshida and Yasuhisa Fujita
Coatings 2022, 12(1), 57; https://doi.org/10.3390/coatings12010057 - 04 Jan 2022
Cited by 3 | Viewed by 2150
Abstract
Various annealing atmospheres were employed during our unique thermal-diffusion type Ga-doping process to investigate the surface, structural, optical, and electrical properties of Ga-doped zinc oxide (ZnO) nanoparticle (NP) layers. ZnO NPs were synthesized using an arc-discharge-mediated gas evaporation method, followed by Ga-doping under [...] Read more.
Various annealing atmospheres were employed during our unique thermal-diffusion type Ga-doping process to investigate the surface, structural, optical, and electrical properties of Ga-doped zinc oxide (ZnO) nanoparticle (NP) layers. ZnO NPs were synthesized using an arc-discharge-mediated gas evaporation method, followed by Ga-doping under open-air, N2, O2, wet, and dry air atmospheric conditions at 800 °C to obtain the low resistive spray-coated NP layers. The I–V results revealed that the Ga-doped ZnO NP layer successfully reduced the sheet resistance in the open air (8.0 × 102 Ω/sq) and wet air atmosphere (8.8 × 102 Ω/sq) compared with un-doped ZnO (4.6 × 106 Ω/sq). Humidity plays a key role in the successful improvement of sheet resistance during Ga-doping. X-ray diffraction patterns demonstrated hexagonal wurtzite structures with increased crystallite sizes of 103 nm and 88 nm after doping in open air and wet air atmospheres, respectively. The red-shift of UV intensity indicates successful Ga-doping, and the atmospheric effects were confirmed through the analysis of the defect spectrum. Improved electrical conductivity was also confirmed using the thin-film-transistor-based structure. The current controllability by applying the gate electric-field was also confirmed, indicating the possibility of transistor channel application using the obtained ZnO NP layers. Full article
(This article belongs to the Special Issue New Advances in Thin-Film Transistor)
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12 pages, 6058 KiB  
Article
Effect of HfO2-Based Multi-Dielectrics on Electrical Properties of Amorphous In-Ga-Zn-O Thin Film Transistors
by Ruozheng Wang, Qiang Wei, Jie Li, Jiao Fu, Yiwei Liu, Tianfei Zhu, Cui Yu, Gang Niu, Shengli Wu and Hongxing Wang
Coatings 2021, 11(11), 1381; https://doi.org/10.3390/coatings11111381 - 11 Nov 2021
Viewed by 1875
Abstract
We report the fabrication of bottom gate a-IGZO TFTs based on HfO2 stacked dielectrics with decent electrical characteristics and bias stability. The microscopic, electrical, and optical properties of room temperature deposited a-IGZO film with varied oxygen content were explored. In order to [...] Read more.
We report the fabrication of bottom gate a-IGZO TFTs based on HfO2 stacked dielectrics with decent electrical characteristics and bias stability. The microscopic, electrical, and optical properties of room temperature deposited a-IGZO film with varied oxygen content were explored. In order to suppress the bulk defects in the HfO2 thin film and hence maximize the quality, surface modification of the SiNx film was investigated so as to achieve a more uniform layer. The root mean square (RMS) roughness of SiNx/HfO2/SiNx (SHS) stacked dielectrics was only 0.66 nm, which was reduced by 35% compared with HfO2 single film (1.04 nm). The basic electrical characteristics of SHS-based a-IGZO TFT were as follows: Vth is 2.4 V, μsat is 21.1 cm2 V−1 s−1, Ion/Ioff of 3.3 × 107, Ioff is 10−11 A, and SS is 0.22 V/dec. Zr-doped HfO2 could form a more stable surface, which will decrease the bulk defect states so that the stability of device can be improved. It was found that the electrical characteristics were improved after Zr doping, with a Vth of 1.4 V, Ion/Ioff of 108, μsat of 19.5 cm2 V−1 s−1, Ioff of 10−12 A, SS of 0.18 V/dec. After positive gate bias stress of 104 s, the ΔVth was decreased from 0.43 V (without Zr doping) to 0.09 V (with Zr doping), the ΔSS was decreased from 0.19 V/dec to 0.057 V/dec, respectively, which shows a meaningful impact to realize the long-term working stability of TFT devices. Full article
(This article belongs to the Special Issue New Advances in Thin-Film Transistor)
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12 pages, 3914 KiB  
Article
Ion Sensitive GO-Si Based Metal-Semiconductor Junction Resistor Gas Sensor
by Yi Zhao, Deyin Zhao, Zhenzhen Ma, Gong Li, Dan Zhao and Xin Li
Coatings 2021, 11(11), 1310; https://doi.org/10.3390/coatings11111310 - 28 Oct 2021
Viewed by 1394
Abstract
Gas sensor based on the Ultraviolet and Ozone (UVO) treated Chemical Vapor Deposition (CVD) Graphene Oxide (GO) and the Ion Sensitive GO-Si based metal-semiconductor junction resistor was designed and realized. Under different gate voltages, the response characteristics of the sensor to ammonia concentration, [...] Read more.
Gas sensor based on the Ultraviolet and Ozone (UVO) treated Chemical Vapor Deposition (CVD) Graphene Oxide (GO) and the Ion Sensitive GO-Si based metal-semiconductor junction resistor was designed and realized. Under different gate voltages, the response characteristics of the sensor to ammonia concentration, as well as the selectivity and stability of the sensor were studied. The test results show that the comprehensive performance of the gas sensor is the best when the UVO processing time is 1 min and the applied gate voltage is −9 V. The proposed Ion Sensitive GO-Si based metal-semiconductor junction resistor Gas Sensor can detect 250 ppb ammonia with a sensitivity of 4%. The detection limit of the sensor is 50 ppb. Using acetone and ethanol as contrast gases, the sensor shows better selectivity for ammonia. The sensitivity retention rate of the sensor after 10 days is higher than 70%, which indicates that the sensor has a good retention performance. Full article
(This article belongs to the Special Issue New Advances in Thin-Film Transistor)
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9 pages, 1600 KiB  
Article
Comparative Study on the Separate Extraction of Interface and Bulk Trap Densities in Indium Gallium Zinc Oxide Thin-Film Transistors Using Capacitance–Voltage and Current–Voltage Characteristics
by Dong-Ho Lee, Dae-Hwan Kim, Hwan-Seok Jeong, Seong-Hyun Hwang, Sunhee Lee, Myeong-Ho Kim, Jun Hyung Lim and Hyuck-In Kwon
Coatings 2021, 11(9), 1135; https://doi.org/10.3390/coatings11091135 - 18 Sep 2021
Cited by 2 | Viewed by 3453
Abstract
The interface and bulk trap densities were separately extracted from self-aligned top-gate (SA-TG) coplanar indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) using the low-frequency capacitance–voltage (CV) characteristics and space-charge-limited current (SCLC) under the flat-band condition. In the method [...] Read more.
The interface and bulk trap densities were separately extracted from self-aligned top-gate (SA-TG) coplanar indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) using the low-frequency capacitance–voltage (CV) characteristics and space-charge-limited current (SCLC) under the flat-band condition. In the method based on the CV curve, the energy distribution of the interface trap density was extracted using the low-frequency CV characteristics, and that of the bulk trap density was obtained by subtracting the density of interface trap states from the total subgap density of states (DOS) at each energy level. In the SCLC-based method, the energy distribution of the bulk trap density was extracted using the SCLC under the flat-band condition at high drain-to-source voltages, and that of the interface trap density was obtained by subtracting the density of bulk trap components from the total subgap DOS at each energy level. In our experiments, the two characterization techniques provided very similar interface and bulk trap densities and showed that approximately 60% of the subgap states originate from the IGZO/SiO2 interface at the conduction band edge in the fabricated IGZO TFTs, although the two characterization techniques are based on different measurement data. The results of this study confirm the validity of the characterization techniques proposed to separately extract the interface and bulk trap densities in IGZO TFTs. Furthermore, these results show that it is important to reduce the density of interface trap states to improve the electrical performance and stability of fabricated SA-TG coplanar IGZO TFTs. Full article
(This article belongs to the Special Issue New Advances in Thin-Film Transistor)
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10 pages, 2837 KiB  
Article
Effects of Oxygen Content on Operational Characteristics and Stability of High-Mobility IGTO Thin-Film Transistors during Channel Layer Deposition
by Hwan-Seok Jeong, Hyun-Seok Cha, Seong-Hyun Hwang, Dong-Ho Lee, Sang-Hun Song and Hyuck-In Kwon
Coatings 2021, 11(6), 698; https://doi.org/10.3390/coatings11060698 - 10 Jun 2021
Cited by 9 | Viewed by 2775
Abstract
In this study, we investigated the effects of oxygen content on the transfer characteristics and stability of high-mobility indium-gallium-tin oxide (IGTO) thin-film transistors (TFTs) during channel layer deposition. The IGTO thin films were deposited through direct current sputtering at different ambient oxygen percentages [...] Read more.
In this study, we investigated the effects of oxygen content on the transfer characteristics and stability of high-mobility indium-gallium-tin oxide (IGTO) thin-film transistors (TFTs) during channel layer deposition. The IGTO thin films were deposited through direct current sputtering at different ambient oxygen percentages of 10%, 20%, 30%, 40%, and 50%. The experimental results indicate that the drain currents were hardly modulated by the gate-to-source voltage in the IGTO TFT prepared at 10% ambient oxygen. However, as the oxygen content increased from 20% to 50%, the transfer curves shifted to the positive direction with a decrease in field-effect mobility (μFE). The IGTO TFTs exhibited deteriorated positive bias stress (PBS) stability as the oxygen content increased. However, the stabilities of the IGTO TFTs under negative bias illumination stress (NBIS) improved with an increase in the ambient oxygen percentage during the channel layer deposition. Furthermore, to understand the mechanism of the observed phenomena, we performed X-ray photoelectron spectroscopy (XPS) analysis of the IGTO thin films prepared at different oxygen percentages. The XPS results demonstrate that the deteriorated PBS stability and enhanced NBIS stability of the IGTO TFTs prepared at higher oxygen percentages were mainly ascribed to the larger amount of oxygen interstitials resulting from the excess oxygen and the smaller number of oxygen vacancies within the IGTO, respectively. The obtained results suggest that the oxygen percentages of 30% in the sputtering ambient is the most suitable oxygen percentage for optimizing the electrical properties (μFE = 24.2 cm2/V·s, subthreshold swing = 0.43 V/dec, and threshold voltage = −2.2 V) and adequate PBS and NBIS stabilities of IGTO TFTs. Full article
(This article belongs to the Special Issue New Advances in Thin-Film Transistor)
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17 pages, 2537 KiB  
Article
High-Entropy Oxides: Advanced Research on Electrical Properties
by Haoyang Li, Yue Zhou, Zhihao Liang, Honglong Ning, Xiao Fu, Zhuohui Xu, Tian Qiu, Wei Xu, Rihui Yao and Junbiao Peng
Coatings 2021, 11(6), 628; https://doi.org/10.3390/coatings11060628 - 24 May 2021
Cited by 32 | Viewed by 6661
Abstract
The concept of “high entropy” was first proposed while exploring the unknown center of the metal alloy phase diagram, and then expanded to oxides. The colossal dielectric constant found on the bulk high-entropy oxides (HEOs) reveals the potential application of the high-entropy oxides [...] Read more.
The concept of “high entropy” was first proposed while exploring the unknown center of the metal alloy phase diagram, and then expanded to oxides. The colossal dielectric constant found on the bulk high-entropy oxides (HEOs) reveals the potential application of the high-entropy oxides in the dielectric aspects. Despite the fact that known HEO thin films have not been reported in the field of dielectric properties so far, with the high-entropy effects and theoretical guidance of high entropy, it is predictable that they will be discovered. Currently, researchers are verifying that appropriately increasing the oxygen content in the oxide, raising the temperature and raising the pressure during preparation have an obvious influence on thin films’ resistivity, which may be the guidance on obtaining an HEO film large dielectric constant. Finally, it could composite a metal–insulator–metal capacitor, and contribute to sensors and energy storage devices’ development; alternatively, it could be put into application in emerging thin-film transistor technologies, such as those based on amorphous metal oxide semiconductors, semiconducting carbon nanotubes, and organic semiconductors. Full article
(This article belongs to the Special Issue New Advances in Thin-Film Transistor)
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13 pages, 6562 KiB  
Article
The Investigation of Indium-Free Amorphous Zn-Al-Sn-O Thin Film Transistor Prepared by Magnetron Sputtering
by Mingyu Zhang, Kuankuan Lu, Zhuohui Xu, Honglong Ning, Xiaochen Zhang, Junlong Chen, Zhao Yang, Xuan Zeng, Rihui Yao and Junbiao Peng
Coatings 2021, 11(5), 585; https://doi.org/10.3390/coatings11050585 - 17 May 2021
Cited by 2 | Viewed by 2465
Abstract
The indium-free amorphous oxide semiconductor thin film transistor (AOS-TFT) with aluminum (Al) electrodes shows broad application prospects in new-generation display technologies, such as ultra-high definition large-screen display, OLED display and 3D display. In this work, the thin film transistor (TFT) with a zinc-aluminum-tin-oxide [...] Read more.
The indium-free amorphous oxide semiconductor thin film transistor (AOS-TFT) with aluminum (Al) electrodes shows broad application prospects in new-generation display technologies, such as ultra-high definition large-screen display, OLED display and 3D display. In this work, the thin film transistor (TFT) with a zinc-aluminum-tin-oxide (ZATO) semiconductor as the active layer and an Al electrodes as the source and drain (S/D) was investigated. The optical, electrical and semiconductive properties of the ZATO films were evaluated by atomic force microscopy (AFM), ultraviolet–visible spectrophotometry and microwave photoconductivity decay (μ-PCD), respectively. The result shows that the film is smooth and transparent and has low localized states and defects at a moderate oxygen concentration (~5%) and a low sputtering gas pressure (~3 mTorr). After the analysis of the transfer and output characteristics, it can be concluded that the device exhibits an optimal performance at the 623 K annealing temperature with an Ion/Ioff ratio of 5.5 × 107, an SS value of 0.15 V/decade and a saturation mobility (μsat) of 3.73 cm2·V−1·s−1. The ZATO TFT at the 623 K annealing has a −8.01 V negative shift under the −20 V NBS and a 2.66 V positive shift under the 20 V PBS. Full article
(This article belongs to the Special Issue New Advances in Thin-Film Transistor)
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8 pages, 3301 KiB  
Article
Reliable Ohmic Contact Properties for Ni/Hydrogen-Terminated Diamond at Annealing Temperature up to 900 °C
by Xiaolu Yuan, Jiangwei Liu, Jinlong Liu, Junjun Wei, Bo Da, Chengming Li and Yasuo Koide
Coatings 2021, 11(4), 470; https://doi.org/10.3390/coatings11040470 - 17 Apr 2021
Viewed by 2206
Abstract
Ohmic contact with high thermal stability is essential to promote hydrogen-terminated diamond (H-diamond) electronic devices for high-temperature applications. Here, the ohmic contact characteristics of Ni/H-diamond at annealing temperatures up to 900 °C are investigated. The measured current–voltage curves and deduced specific contact resistance [...] Read more.
Ohmic contact with high thermal stability is essential to promote hydrogen-terminated diamond (H-diamond) electronic devices for high-temperature applications. Here, the ohmic contact characteristics of Ni/H-diamond at annealing temperatures up to 900 °C are investigated. The measured current–voltage curves and deduced specific contact resistance (ρC) are used to evaluate the quality of the contact properties. Schottky contacts are formed for the as-received and 300 °C-annealed Ni/H-diamonds. When the annealing temperature is increased to 500 °C, the ohmic contact properties are formed with the ρC of 1.5 × 10−3 Ω·cm2 for the Ni/H-diamond. As the annealing temperature rises to 900 °C, the ρC is determined to be as low as 6.0 × 10−5 Ω·cm2. It is believed that the formation of Ni-related carbides at the Ni/H-diamond interface promotes the decrease in ρC. The Ni metal is extremely promising to be used as the ohmic contact electrode for the H-diamond-based electronic devices at temperature up to 900 °C. Full article
(This article belongs to the Special Issue New Advances in Thin-Film Transistor)
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