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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06 Apr 2020
TL;DR: The manipulation of donor-like defects, including generation, suppression and diffusion, in metal oxide (MO) thin-film transistors (TFTs) has been reviewed systematically.
Abstract: The manipulation of donor-like defects, including generation, suppression and diffusion, in metal oxide (MO) thin-film transistors (TFTs) has been reviewed systematically. Based on this, the defect-populated source/drain (S/D) regions and defect-free channel region are realized for high-performance TFTs, and even the location of self-aligned (SA) homojunctions can be accurately controlled.
1 citations
TL;DR: In this paper, a decreasing work function is considered for the carbon-based materials, which can be theoretically obtained by increasing the number of free electrons in the material due to the increase in the Fermi energy levels.
Abstract: DOI: 10.1002/aelm.201800046 semiconductor have been considered for use as the S/D of the TFTs.[7] Sputtered Mo has a high stability against an oxidative atmosphere,[8] and it shows a high uniformity in its performance.[9] However, Mo still has a problem regarding its transparency when applied in flexible transparent electronics. Therefore, many flexible transparent electrodes (FTEs), including organic conductors, metal nanowire networks, and carbon-based materials, have also been studied. Conducting polymers such as poly 3,4-ethylene-dioxythiophene : polystyrene sulfonate (PEDOT:PSS) shows low resistivity (≈2.3 × 10−4 Ω cm) and a high transparency.[10] However, these have a fundamental limit on their transparency due to the low bandgap (<3 eV), and they can also be easily oxidized by the surrounding air.[11] Furthermore, PEDOT:PSS has a high work function of 5.0–5.4 eV,[12,13] and it limits the use on S/D with an n-type semiconductor. Metal nanowire (NW) networks such as Ag NW networks also have shown a lower sheet resistance (≈10 Ω sq−1), high transparency (≈95%),[14] and work function of 4.0–4.2 eV[14,15] which is in the appropriate range for matching with n-type semiconductors. However, the fabrication process is complex, and it still has a high roughness, resulting in the additional coating of an organic conductor with an increase in the work function of over 4.5 eV.[16] In addition, the weak adhesion on the plastic substrate, high contact resistance between nanowires, and oxidation against air are also limits of the Ag NW network.[17] In general, the carbon-based materials have promising properties such as abundance, high mechanical strength, high flexibility, high stability against the air and chemicals, low resistance, and high transparency. Graphene consisting of pure carbon has a work function of 4.5 eV,[18,19] and this value is a little high for the n-type semiconductor contact. Therefore, a decreasing work function is considered for the carbon-based materials. The low work function can be theoretically obtained by increasing the number of free electrons in the material due to the increase in the Fermi energy levels. For carbon-based materials, nitrogen has one more electron than carbon, and it can be a substitutional dopant that gives rise to an increase in the delocalized electron concentration, resulting in a decrease in the work function.[20,21] By incorporating nitrogen-doped carbonbased materials, the device performance indeed improves Oxide semiconductors are one of the key components for flexible and transparent electronics, but their use has been limited by the work function of contact materials. Carbon-based materials are strong candidates for flexible transparent electrodes, and nitrogen-doped carbon materials have been specifically investigated due to the controllability of their work function. Of the many methods to dop nitrogen, the pyrolysis of biomolecules is a particular focus since it is a simple, inexpensive process that yields a high atomic percent of nitrogen. Polydopamine (pDop), which is inspired by adhesive proteins in mussels, has been suggested for use as a precursor for pyrolysis, and the pyrolyzed pDop–Cu hybrid film shows the lowest resistivity (1.4 × 10−4 Ω cm) in pyrolyzed carbon so far, for which copper chelation is attributed to reduction in resistivity. The pyrolyzed film also shows a transparency of 84%, and it is stable in cyclic bending tests up to 105 cycles. The films are further applied to the source and drain of a field-effect transistor, and the devices achieve a high performance that is comparable to that from molybdenum contacted device, with the work function ranging from 4.51 to 4.31 eV.
1 citations
TL;DR: In this article , a top-gate insulator of atomic layer-deposited (ALD) HfOx was developed for the amorphous indium-gallium-zinc oxide (a-IGZO) TFTs.
1 citations
TL;DR: It is believed that the hybrid PbSe/ITZO material platform can be widely used to be in favour of incorporation of solution-processed colloidal light absorbing material into the high-performance metal oxide thin film transistor configuration.
Abstract: We report that high absorption PbSe colloidal quantum dots (QDs) having a peak absorbance beyond 2100 nm were synthesized and incorporated into InSnZnO (ITZO) channel layer-based thin film transistors (TFTs). It was intended that PbSe QDs with proportionally less photocurrent modulation can be remedied by semiconducting and low off-current ITZO-based TFT configuration. Multiple deposition scheme of PbSe QDs on ITZO metal oxide thin film gave rise to nearly linear increase of film thickness with acceptably uniform and smooth surface (less than 10 nm). Hybrid PbSe/ITZO thin film-based phototransistor exhibited the best performance of near infrared (NIR) detection in terms of response time, sensitivity and detectivity as high as 0.38 s, 3.91 and 4.55 × 107 Jones at room temperature, respectively. This is indebted mainly from the effective diffusion of photogenerated carrier from the PbSe surface to ITZO channel layer as well as from the conduction band alignment between them. Therefore, we believe that our hybrid PbSe/ITZO material platform can be widely used to be in favour of incorporation of solution-processed colloidal light absorbing material into the high-performance metal oxide thin film transistor configuration.
1 citations
TL;DR: In this article , a hybrid functional method was used to investigate the transparency and p-type conductivity of BeSe, and the hole density, induced by NSe (PSe) defects, can reach 4.44 × 1018 (3.83 × 1016) cm.
Abstract: Utilizing a hybrid functional method, the transparency and p-type conductivity of BeSe are investigated. Our studies confirm that N- and P-substituted Se (labeled as NSe and PSe) are promising p-type defects due to their smaller ionization energy. BeN2 and BeP2 are efficient dopant sources for their moderate formation energy. Based on the thermodynamic equilibrium fabrication method together with the rapidly quenching scheme, we find the hole density, induced by NSe (PSe) defects, can reach 4.44 × 1018 (3.83 × 1016) cm–3. A high density of holes, smaller hole effective mass (along the Γ-X and W-X directions, the hole effective masses are 0.466 and 0.759m0 (m0 is the electron’s static mass)), wide band gap, and weak plasmonic effect show that BeSe with NSe defects is an excellent transparent p-type semiconductor. These findings provide significant insight to explore a transparent p-type semiconductor.
1 citations
References
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TL;DR: A novel semiconducting material is proposed—namely, a transparent amorphous oxide semiconductor from the In-Ga-Zn-O system (a-IGZO)—for the active channel in transparent thin-film transistors (TTFTs), which are fabricated on polyethylene terephthalate sheets and exhibit saturation mobilities and device characteristics are stable during repetitive bending of the TTFT sheet.
Abstract: Transparent electronic devices formed on flexible substrates are expected to meet emerging technological demands where silicon-based electronics cannot provide a solution. Examples of active flexible applications include paper displays and wearable computers1. So far, mainly flexible devices based on hydrogenated amorphous silicon (a-Si:H)2,3,4,5 and organic semiconductors2,6,7,8,9,10 have been investigated. However, the performance of these devices has been insufficient for use as transistors in practical computers and current-driven organic light-emitting diode displays. Fabricating high-performance devices is challenging, owing to a trade-off between processing temperature and device performance. Here, we propose to solve this problem by using a novel semiconducting material—namely, a transparent amorphous oxide semiconductor from the In-Ga-Zn-O system (a-IGZO)—for the active channel in transparent thin-film transistors (TTFTs). The a-IGZO is deposited on polyethylene terephthalate at room temperature and exhibits Hall effect mobilities exceeding 10 cm2 V-1 s-1, which is an order of magnitude larger than for hydrogenated amorphous silicon. TTFTs fabricated on polyethylene terephthalate sheets exhibit saturation mobilities of 6–9 cm2 V-1 s-1, and device characteristics are stable during repetitive bending of the TTFT sheet.
7,301 citations
Book•
04 Jul 1990
TL;DR: In this article, the authors present a characterization of the resistivity of a two-point-versus-four-point probe in terms of the number of contacts and the amount of contacts in the probe.
Abstract: Preface to Third Edition. 1 Resistivity. 1.1 Introduction. 1.2 Two-Point Versus Four-Point Probe. 1.3 Wafer Mapping. 1.4 Resistivity Profiling. 1.5 Contactless Methods. 1.6 Conductivity Type. 1.7 Strengths and Weaknesses. Appendix 1.1 Resistivity as a Function of Doping Density. Appendix 1.2 Intrinsic Carrier Density. References. Problems. Review Questions. 2 Carrier and Doping Density. 2.1 Introduction. 2.2 Capacitance-Voltage (C-V). 2.3 Current-Voltage (I-V). 2.4 Measurement Errors and Precautions. 2.5 Hall Effect. 2.6 Optical Techniques. 2.7 Secondary Ion Mass Spectrometry (SIMS). 2.8 Rutherford Backscattering (RBS). 2.9 Lateral Profiling. 2.10 Strengths and Weaknesses. Appendix 2.1 Parallel or Series Connection? Appendix 2.2 Circuit Conversion. References. Problems. Review Questions. 3 Contact Resistance and Schottky Barriers. 3.1 Introduction. 3.2 Metal-Semiconductor Contacts. 3.3 Contact Resistance. 3.4 Measurement Techniques. 3.5 Schottky Barrier Height. 3.6 Comparison of Methods. 3.7 Strengths and Weaknesses. Appendix 3.1 Effect of Parasitic Resistance. Appendix 3.2 Alloys for Contacts to Semiconductors. References. Problems. Review Questions. 4 Series Resistance, Channel Length and Width, and Threshold Voltage. 4.1 Introduction. 4.2 PN Junction Diodes. 4.3 Schottky Barrier Diodes. 4.4 Solar Cells. 4.5 Bipolar Junction Transistors. 4.6 MOSFETS. 4.7 MESFETS and MODFETS. 4.8 Threshold Voltage. 4.9 Pseudo MOSFET. 4.10 Strengths and Weaknesses. Appendix 4.1 Schottky Diode Current-Voltage Equation. References. Problems. Review Questions. 5 Defects. 5.1 Introduction. 5.2 Generation-Recombination Statistics. 5.3 Capacitance Measurements. 5.4 Current Measurements. 5.5 Charge Measurements. 5.6 Deep-Level Transient Spectroscopy (DLTS). 5.7 Thermally Stimulated Capacitance and Current. 5.8 Positron Annihilation Spectroscopy (PAS). 5.9 Strengths and Weaknesses. Appendix 5.1 Activation Energy and Capture Cross-Section. Appendix 5.2 Time Constant Extraction. Appendix 5.3 Si and GaAs Data. References. Problems. Review Questions. 6 Oxide and Interface Trapped Charges, Oxide Thickness. 6.1 Introduction. 6.2 Fixed, Oxide Trapped, and Mobile Oxide Charge. 6.3 Interface Trapped Charge. 6.4 Oxide Thickness. 6.5 Strengths and Weaknesses. Appendix 6.1 Capacitance Measurement Techniques. Appendix 6.2 Effect of Chuck Capacitance and Leakage Current. References. Problems. Review Questions. 7 Carrier Lifetimes. 7.1 Introduction. 7.2 Recombination Lifetime/Surface Recombination Velocity. 7.3 Generation Lifetime/Surface Generation Velocity. 7.4 Recombination Lifetime-Optical Measurements. 7.5 Recombination Lifetime-Electrical Measurements. 7.6 Generation Lifetime-Electrical Measurements. 7.7 Strengths and Weaknesses. Appendix 7.1 Optical Excitation. Appendix 7.2 Electrical Excitation. References. Problems. Review Questions. 8 Mobility. 8.1 Introduction. 8.2 Conductivity Mobility. 8.3 Hall Effect and Mobility. 8.4 Magnetoresistance Mobility. 8.5 Time-of-Flight Drift Mobility. 8.6 MOSFET Mobility. 8.7 Contactless Mobility. 8.8 Strengths and Weaknesses. Appendix 8.1 Semiconductor Bulk Mobilities. Appendix 8.2 Semiconductor Surface Mobilities. Appendix 8.3 Effect of Channel Frequency Response. Appendix 8.4 Effect of Interface Trapped Charge. References. Problems. Review Questions. 9 Charge-based and Probe Characterization. 9.1 Introduction. 9.2 Background. 9.3 Surface Charging. 9.4 The Kelvin Probe. 9.5 Applications. 9.6 Scanning Probe Microscopy (SPM). 9.7 Strengths and Weaknesses. References. Problems. Review Questions. 10 Optical Characterization. 10.1 Introduction. 10.2 Optical Microscopy. 10.3 Ellipsometry. 10.4 Transmission. 10.5 Reflection. 10.6 Light Scattering. 10.7 Modulation Spectroscopy. 10.8 Line Width. 10.9 Photoluminescence (PL). 10.10 Raman Spectroscopy. 10.11 Strengths and Weaknesses. Appendix 10.1 Transmission Equations. Appendix 10.2 Absorption Coefficients and Refractive Indices for Selected Semiconductors. References. Problems. Review Questions. 11 Chemical and Physical Characterization. 11.1 Introduction. 11.2 Electron Beam Techniques. 11.3 Ion Beam Techniques. 11.4 X-Ray and Gamma-Ray Techniques. 11.5 Strengths and Weaknesses. Appendix 11.1 Selected Features of Some Analytical Techniques. References. Problems. Review Questions. 12 Reliability and Failure Analysis. 12.1 Introduction. 12.2 Failure Times and Acceleration Factors. 12.3 Distribution Functions. 12.4 Reliability Concerns. 12.5 Failure Analysis Characterization Techniques. 12.6 Strengths and Weaknesses. Appendix 12.1 Gate Currents. References. Problems. Review Questions. Appendix 1 List of Symbols. Appendix 2 Abbreviations and Acronyms. Index.
6,573 citations
TL;DR: In this paper, a review of the literature in the area of alternate gate dielectrics is given, based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward success.
Abstract: Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 μm complementary metal–oxide–semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward success...
5,711 citations
IBM1
TL;DR: In this article, the authors present new insight into conduction mechanisms and performance characteristics, as well as opportunities for modeling properties of organic thin-film transistors (OTFTs) and discuss progress in the growing field of n-type OTFTs.
Abstract: Organic thin-film transistors (OTFTs) have lived to see great improvements in recent years. This review presents new insight into conduction mechanisms and performance characteristics, as well as opportunities for modeling properties of OTFTs. The shifted focus in research from novel chemical structures to fabrication technologies that optimize morphology and structural order is underscored by chapters on vacuum-deposited and solution-processed organic semiconducting films. Finally, progress in the growing field of the n-type OTFTs is discussed in ample detail. The Figure, showing a pentacene film edge on SiO2, illustrates the morphology issue.
4,804 citations
TL;DR: An outlook is presented on what will be required to drive this young photovoltaic technology towards the next major milestone, a 10% power conversion efficiency, considered by many to represent the efficiency at which OPV can be adopted in wide-spread applications.
Abstract: Solution-processed bulk-heterojunction solar cells have gained serious attention during the last few years and are becoming established as one of the future photovoltaic technologies for low-cost power production. This article reviews the highlights of the last few years, and summarizes today's state-of-the-art performance. An outlook is given on relevant future materials and technologies that have the potential to guide this young photovoltaic technology towards the magic 10% regime. A cost model supplements the technical discussions, with practical aspects any photovoltaic technology needs to fulfil, and answers to the question as to whether low module costs can compensate lower lifetimes and performances.
3,084 citations