Oxide Semiconductor Thin‐Film Transistors: A Review of Recent Advances
TL;DR: The recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed andp-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed.
Abstract: Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n- and p-type oxide transistors as well as the fabrication of CMOS devices with and on paper.
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TL;DR: The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed in this article.
Abstract: Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (e) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.
1,535 citations
TL;DR: This Review surveys the uniqueness and universality of MOs versus other unconventional electronic materials in terms of materials chemistry and physics, electronic characteristics, thin-film fabrication strategies and selected applications in thin- film transistors, solar cells, diodes and memories.
Abstract: Optical transparency, tunable conducting properties and easy processability make metal oxides key materials for advanced optoelectronic devices. This Review discusses recent advances in the synthesis of these materials and their use in applications. Metal oxides (MOs) are the most abundant materials in the Earth's crust and are ingredients in traditional ceramics. MO semiconductors are strikingly different from conventional inorganic semiconductors such as silicon and III–V compounds with respect to materials design concepts, electronic structure, charge transport mechanisms, defect states, thin-film processing and optoelectronic properties, thereby enabling both conventional and completely new functions. Recently, remarkable advances in MO semiconductors for electronics have been achieved, including the discovery and characterization of new transparent conducting oxides, realization of p-type along with traditional n-type MO semiconductors for transistors, p–n junctions and complementary circuits, formulations for printing MO electronics and, most importantly, commercialization of amorphous oxide semiconductors for flat panel displays. This Review surveys the uniqueness and universality of MOs versus other unconventional electronic materials in terms of materials chemistry and physics, electronic characteristics, thin-film fabrication strategies and selected applications in thin-film transistors, solar cells, diodes and memories.
1,098 citations
TL;DR: This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions.
Abstract: Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol–gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual...
841 citations
TL;DR: In this review, recent progress in materials and devices for future wearable sensor technologies for bio and medical applications are reported.
Abstract: Printable electronics present a new era of wearable electronic technologies. Detailed technologies consisting of novel ink semiconductor materials, flexible substrates, and unique processing methods can be integrated to create flexible sensors. To detect various stimuli of the human body, as well as specific environments, unique electronic devices formed by "ink-based semiconductors" onto flexible and/or stretchable substrates have become a major research trend in recent years. Materials such as inorganic, organic, and hybrid semiconductors with various structures (i.e., 1D, 2D and 3D) with printing capabilities have been considered for bio and medical applications. In this review, we report recent progress in materials and devices for future wearable sensor technologies.
589 citations
TL;DR: In this article, the recent progress in n-and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p type, and the major milestones already achieved with this emerging and very promising technology are summarized.
Abstract: Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n- and p-type oxide transistors as well as the fabrication of CMOS devices with and on paper.
529 citations
References
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TL;DR: In this paper, a comparative study of low-frequency noise in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors with Al2O3 and Al 2O3/SiNx gate dielectrics is made.
Abstract: A comparative study is made of the low-frequency noise (LFN) in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with Al2O3 and Al2O3/SiNx gate dielectrics. The LFN is proportional to 1/fgamma, with gamma ~ 1 for both devices, but the normalized noise for the Al2O3/SiNx device is two to three orders of magnitude lower than that for the Al2O3 device. The mobility fluctuation is the dominant LFN mechanism in both devices, but the noise from the source/drain contacts becomes comparable to the intrinsic channel noise as the gate overdrive voltage increases in Al2O3/SiNx devices. The SiNx interfacial layer is considered to be very effective in reducing LFN by suppressing the remote phonon scattering from the Al2O3 dielectric. Hooge's parameter is extracted to ~6.0 times 10-3 in Al2O3/SiNx devices.
39 citations
TL;DR: In this article, the electrical resistivity and the carrier density of the a-IGZO film showed large variations with changes in the substrate temperature or the oxygen pressure, and the optical transmittance showed a clear variation in the violet color region.
Abstract: and scanning electron microscopy data suggest that the a-IGZO starts to crystallize around 600 C. The electrical resistivity and the carrier density of the a-IGZO film showed large variations with changes in the substrate temperature or the oxygen pressure. The resistivity of the a-IGZO film was minimized at 200 C and 10 mTorr. The energy gap estimated from the optical transmittance showed an increasing tendency with increasing of substrate temperature up to 200 C or with increasing of oxygen pressure up to 100 mTorr, and it was about 3.0 eV at 200 C and 10 mTorr. Remarkably, the optical transmittance for the a-IGZO film showed a clear variation in the violet color region with changing of the substrate temperature and oxygen pressure. Our results suggest that both the substrate temperature and the oxygen pressure can be exploited as key parameters to control the electrical and the optical properties of a-IGZO films.
39 citations
TL;DR: In this article, transparent bottom-gate TFTs (thin film transistors) using amorphous IGZO (In-Ga-Zn-O) as an active channel material were studied.
Abstract: We have studied transparent bottom-gate TFTs (thin film transistors) using amorphous IGZO (In-Ga-Zn-O) as an active channel material. The TFT devices had inverse co-planar structures. Source/drain and gate electrodes were constituted by ITO sputtered with a DC-RF magnetron sputter system, and an alkaline-free glass was used as a substrate. The gate insulator was Al2O3 formed by using an atomic layer deposition (ALD) method at 150 ◦C. An active layer was formed by off-axis RF magnetron sputtering and post-annealing was performed with a hot plate or a vacuum oven. The field effect mobilities and the sub-threshold swings of the IGZO TFTs were 12 ∼ 18 cm/Vs and 0.2 ∼ 0.6 V/dec, respectively. However, the hysteresis on I-V characteristics was relatively large without passivation. Thus, we passivated the TFT devices with inorganic and organic materials. After the organic passivation and post-heat treatments, the hysteresis was remarkably reduced without deterioration of the electrical characteristics.
38 citations
TL;DR: In this article, scaling effects on the electrical properties of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) were investigated.
37 citations
TL;DR: In this article, a low-cost Al-doped ZnO (AZO) thin film was deposited by radio-frequency magnetron sputtering with different Ar/O2 flow ratios.
Abstract: A low-cost Al-doped ZnO (AZO) thin film was deposited by radio-frequency magnetron sputtering with different Ar/O2 flow ratios. The optical and electrical properties of an AZO film were investigated. A highly conductive AZO film was inserted between the amorphous InGaZnO (a-IGZO) channel and the metal Al electrode to form a heterojunction source/drain contact, and bottom-gate amorphous a-IGZO thin-film transistors (TFTs) with a high κ HfON gate dielectric were fabricated. The AZO film reduced the source/drain contact resistivity down to 79 Ω cm. Enhanced device performance of a-IGZO TFT with Al/AZO bi-layer S/D electrodes (W/L = 500/40 µm) was achieved with a saturation mobility of 13.7 cm2 V−1 s−1, a threshold voltage of 0.6 V, an on-off current ratio of 4.7 × 106, and a subthreshold gate voltage swing of 0.25 V dec−1. It demonstrated the potential application of the AZO film as a promising S/D contact material for the fabrication of the high performance TFTs.
37 citations