Kenji Nomura

University of California, San Diego | UCSD

We have seen the electronic structures specific to amorphous oxide semiconductors (AOSs) in Chapters 1–3. Here we will review electronic defects in AOSs that affect operation characteristics and instabilities in AOS thin‐film transistors (TFTs). The energy distributions of the electron traps have been investigated from the capacitance–voltage (C‐V)...

Amorphous oxide semiconductor (AOS) is now commercialized in many flat-panel displays. On the other hand, its electronic structures and defects are largely different from conventional covalent semiconductors such as Si. This chapter explains their origins and reviews the defects that have been known to date. Finally, we will discuss how to fabricat...

Amorphous oxide semiconductors (AOSs) have been commercialized since 2012 as thin‐film transistor (TFT) backplanes in flat‐panel displays. This review first provides a brief history and current status of AOS technology, and then introduces electronic defects in AOSs reported to date that are critically important for understanding and controlling th...

Oxide semiconductor based TFT is to date accepted as a emerging technology that enable the development of next generation display and flexible technologies because of its superior properties and wide compatibility of processing. However, the largest drawback is the absence of high performance p-channel oxide-TFT. Here we review the recent progress...

We report operation characteristics of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) annealed in dry ${{O}} _{2}$ at temperatures up to 700 $^{\circ}{{C}}$ . The largest TFT mobilities were obtained by annealing at 200 $ ^{\circ}{{C}}$ –300 $ ^{\circ}{{C}}$ and the smallest subthreshold voltage swing ( ${\rm S}$ ) was obtained at 200 $...

Background: While the prevalence of child abuse in Japan is low in comparison to other countries, such as the US, the number of reported child abuse incidents in Japan has exploded since 2000. This is in part due to legislation pertaining to reporting, but is also likely due to changes in Japanese society. Methods: This paper describes the Japanese...

The effect of an ambient atmosphere with a positive bias constant current stress (CCS) and a negative bias illumination stress (NBIS) on the stability of amorphous In-Ga-Zn-O thin film transistors (TFTs) is examined by utilizing a glass-hermetic-sealant with a moisture permeability of less than 10−6 g/m2 · day. In the CCS test, the threshold voltag...

We investigated roles of hydrogen on physical properties of a-IGZO films and thin-film transistors (TFTs) by comparing standard and ultra-high vacuum (UHV) sputtering systems. It was confirmed that the impurity hydrogens come mainly from the residual gas in the deposition chamber and the molecules adsorbed to the surface of the sputtering target. I...

We have developed light irradiation and applied voltage history sensors using amorphous In-Ga-Zn-O (oc-IGZO) thin-film transistor (TFTs) exposed to ozone annealing and fabricated under high oxygen pressure. These a-IGZO TFTs have an interesting property; the Ids-Vgs characteristic shifts positively and becomes steep when gate voltage is applied whe...

An isotope tracer study, i.e., 18O/16O exchange using 18O2 and H218O, was performed to determine how post-deposition annealing (PDA) affected surface reactivity and oxygen diffusivity of amorphous indium–gallium–zinc oxide (a-IGZO) films. The oxygen tracer diffusivity was very high in the bulk even at low temperatures, e.g., 200 °C, regardless of P...

We report an experimental evidence that some hydrogens passivate electron traps in an amorphous oxide semiconductor, a-In-Ga-Zn-O (a-IGZO). The a-IGZO thin-film transistors (TFTs) annealed at 300 °C exhibit good operation characteristics; while those annealed at ≥400 °C show deteriorated ones. Thermal desorption spectra (TDS) of H2O indicate that t...

We have developed 3-D stacked complementary TFT devices using n-type α-IGZO and p-type F8T2 TFTs on PET substrates. We confirmed proper I-V characteristics of both the α-IGZO and F8T2 TFTs and correct input-output characteristics of both NOT and NAND logic circuits. The operation confirmation of the NAND logic circuit suggests that any advanced log...

This review paper provides the present status of amorphous oxide semiconductor technology along with knowledge obtained to date on their carrier transport, defects and impurities in relation to their stability issues.

We found that device-quality thin films of amorphous oxide semiconductor, a-In-Ga-Zn-O, unintentionally include high-density hydrogens over 10(20) cm(-3) but the electron concentration remains low at similar to 10(15) cm(-3) in as-deposited states. The hydrogens exist in the form of hydroxyl group -OH, but most of them are inactive as an electron d...

We have developed a maximum applied voltage detector using an α-IGZO TFT exposed to ozone annealing. This TFT has an interesting property; the Ids–Vgs characteristic shifts positively and becomes steep when gate voltage is applied, whereas it recovers the initial one with a small threshold voltage and a large subthreshold swing upon light illuminat...

We fabricated transparent amorphous oxide semiconductor superlattices composed of In-Ga-Zn-O (a-IGZO) well layers and Ga2O3 (a-Ga2O3) barrier layers, and investigated their optical absorption properties to examine energy quantization in the a-IGZO well layer. The Tauc gap of a-IGZO well layers monotonically increases with decreasing well thickness...

Although amorphous InGaZnO{sub 4} has intensively been studied for a semiconductor channel material of thin-film transistors in next-generation flat-panel displays, its electronic structure parameters have not been reported. In this work, the electron affinities ({chi}) and the ionization potentials (I{sub p}) of crystalline and amorphous InGaZnO{s...

We studied the electrical characteristics and electrical stress instabilities of amorphous In–Ga–Zn–O ($a$-IGZO) dual-gate thin-film-transistors (DG TFTs). A threshold voltage of the bottom-gate (BG)-driven $a$-IGZO DG TFTs showed a linear dependence on the top-gate (TG) voltage. The slope of this dependence is associated with the ratio of the TG t...

We developed three-dimensional stacked complementary TFT devices using n-type amorphous In-Ga-Zn-O and p-type poly-(9, 9-dioctylfluorene-co-bithiophene) TFTs. In this presentation, we will report the characteristic shift of the CTFT inverter after temperature and operation stresses. The characteristic shifts extremely negatively after temperature s...

Symposium I / E-MRS Fall Meeting September 2011, Warsaw As world-wide interest in Transparent Electronics appears to be exploiting, there is a need for intense information exchange and platforms for debate in order to facilitate rapid advances on both the materials side and in device fabrication. Symposium I complemented a highly successful series...

Amorphous In-Ga-Zn-O (a-IGZO) is expected as a backplane transistor material to drive next-generation flat-panel and flexible displays. It has been elucidated that thermal annealing even at low temperatures <200 °C reduces deep subgap defects and those at ≥300 °C further improve device characteristics, stability, and uniformity. These temperatures...

Effects of low-temperature annealing were examined for amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs). In a previous study, we reported that O2 annealing is effective to improve performances of a-IGZO TFTs when annealed at ≥300°C, but causes large negative threshold voltage shift when annealed at ≤ 200°C. Here, we examined effects of oz...

We propose a light irradiation history sensor using an amorphous In-Ga-Zn-O ( $\alpha$-IGZO) thin-film transistor (TFT) exposed to ozone annealing at 300 $^{\circ}\hbox{C}$. The $ \alpha$-IGZO TFT has an interesting property. The Ids-Vgs characteristic shifts positively, and the subthreshold slope becomes steep when the gate bias is applied, wherea...

An operation model for an amorphous In–Ga–Zn–O (a-IGZO) based thin film transistor (TFT) is studied. The model is not based on the exponential tail states employed in hydrogenated amorphous Si (a-Si:H) TFT, but on a power function of the carrier density which is observed in the TFT and Hall mobilities of a-IGZO. A 2D numerical simulator employing t...

The stability of amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs) was investigated focusing on the effects of passivation layer materials (Y2O3, Al2O3, HfO2, and SiO2) and thermal annealing. Positive bias constant current stress (CCS), negative bias stress without light illumination (NBS), and negative bias light illumination stress (NBLS...

Photovoltaic properties and electronic structures of n-type amorphous In–Gax–Zn–O/p-type Si heterojunction solar cells (x = 1, 2, and 3) were investigated focusing on the effects of Ga content based on expectation that Ga-rich films have larger band gaps and improve open circuit voltages (VOC) of solar cells. To know the electronic structures such...

Two-dimensionally confined electrons showing unusually large thermopower (S) have attracted attention as a potential approach for developing high performance thermoelectric materials. However, enhanced S has never been observed in electric field induced two-dimensional electron gas (2DEG). Here we demonstrate electric field modulation of S for a fi...

Amorphous In-Ga-Zn-O (a-IGZO) based metal-semiconductor field-effect transistors (MESFETs) were fabricated at 200 degrees C. A bottom Pt structure was employed to form a good Schottky gate, and channel thickness was optimized to 230 nm to obtain high on-currents I-on > 10(-6) A, on-to-off current ratios > 10(6) and low subthreshold voltage swing of...

Oxide semiconductors have been studied very intensively from late '90, and the first commercial product of oxide TFT appeared in this March. This paper reviews the present status and new applications of oxide semiconductors with main focus on amorphous oxide semiconductor. Then, we will discuss clarified knowldges and remaining issues.

We propose a light irradiation history sensor using an amorphous In-Ga-Zn-O (α-IGZO) thin-film transistor (TFT) fabricated by high oxygen partial pressure sputtering. The α-IGZO TFT has an interesting property. The Ids-Vgs characteristic shifts positively, and the subthreshold slope becomes steep when the gate bias is applied, whereas the Ids-Vgs c...

Two-dimensionally confined electrons showing unusually large thermopower (S) have attracted attention as a potential approach for developing high performance thermoelectric materials. However, enhanced S has never been observed in electric field induced two-dimensional electron gas (2DEG). Here we demonstrate electric field modulation of S for a fi...

Diffusion-limited Schottky junctions were fabri- cated at 200 ◦ C by employing a top amorphous In-Ga-Zn-O (a-IGZO)/bottom Pt electrode structure. Those fabricated on glass exhibited rectification ratios of Ion/off > 10 8 and ideality factors close to unity n = 1.04. The temperature dependence values of current-voltage characteristics were small and...

The on operation of an amorphous In-Ga-Zn-O thin-film transistor (a-IGZO TFT) was studied employing a gated-four-probe (GFP) structure TFT to build a simple analytical model based on bias-dependent field-effect mobility (μ_FE). The electrical characteristics of the a-IGZO GFP TFT revealed that the contact resistances were negligible compa...

Export Date: 13 July 2012, Source: Scopus

Operation characteristics of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) were improved to a subthreshold voltage swing (S) of 217 mV (decade)-1, a mobility of ~11.4 cm2 (Vs)-1, and a threshold voltage (Vth) of 0.1 V by O3 annealing at a temperature as low as 150 °C. However, the O3 annealing at 300 °C caused serious deterioration and...

The first ambipolar oxide-based thin-film transistor (TFT) using an SnO channel is presented, demonstrating operation of a complementary-like inverter configured by two ambipolar SnO TFTs. Saturation mobilities of similar to 0.8 and similar to 5 x 10(-4) cm(2) V(-1) s(-1) are obtained for the p-channel and n-channel modes, respectively, and the inv...

In this paper, the (0001) surface of an InGaO3(ZnO)(5) (c-IGZO) single-crystal buffer layer was used as a seed layer to control the orientation of a Si film in solid-phase heteroepitaxial growth at 950 A degrees C. Despite a large lattice misfit of 20%, electron backscattering diffraction (EBSD) and transmission electron microscope (TEM) measuremen...

Highly stable amorphous-In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) against constant current stress and negative bias light illumination stress were realized by forming a Y2O3 passivation layer. A recent photoemission study revealed that deep defects located above the valence band top are formed at a high density to a depth of ~2 nm in the sur...

IntroductionExperimentalResults and DiscussionConclusion

We fabricated transparent oxide semiconductor-based ambipolar TFTs on SiO2/c-Si with a maximum process temperature of 250 °C. Saturation mobilities of ∼0.81 cm2(Vs)−1 for p-channel and ∼5×10−4 cm2(Vs)−1 for n-channel operations were obtained at RT. We demonstrated a complementary-like inverter comprised of two SnO-based ambipolar TFTs. The inverter...

In a previous work, we examined subgap states in highly doped amorphous In-Ga-Zn-O (a-IGZO) films by hard x-ray photoelectron spectroscopy (HX-PES) and found they had subgap electronic states above the valence band maximum (VBM) with the densities > 5 × 1020 cm−3 and just below the Fermi level with the densities > 5 × 1019 cm−3 [K. Nomura, T. Kamiy...

Carrier transport properties and electronic structure of an n-type transparent oxide semiconductor, InGaO3(ZnO)5 were investigated using single-crystalline thin films. Room-temperature Hall mobility strongly depends on carrier concentration, and rapidly increased from ∼ 2 cm2(Vs)-1 to > 10 cm2(Vs) -1 around the carrier concentration (Nth) ∼3 × 1018...

Transparent metal-insulator-semiconductor field-effect transistors (MISFETs) were fabricated using a single-crystalline thin film of an n-type transparent oxide semiconductor, a homologous compound InGaO 3(ZnO)5, grown by a reactive solid phase epitaxy method. The transparent MISFET exhibited good performances with "normally-off characteristics", "...

Operation characteristics of amorphous In-Ga-Zn-O thin-film transistors (TFTs) having very thin channels were studied. TFTs thinner than 10 nm exhibit large mobilities 6-10 cm(2) (Vs)(-1), but that of a 5 nm thick TFT became 1 order of magnitude smaller. Threshold voltage increases with decreasing the channel thickness at < 20 nm. It was confirmed...

The photovoltaic properties and electronic structures of amorphous In-Ga-Zn-O (a-IGZO)/p-type Si heterojunctions were investigated. An optimized solar cell with a conversion efficiency of 5.3% was obtained by vacuum annealing at 300 degrees C. The short circuit current was 28.1 mA.cm(-2), which approaches the theoretical limit without an electron b...

In this study, we have examined the origins of TFT instability against bias and light illumination. We also discuss how we can improve TFT characteristics and stability in relation to defects and the roles of thermal annealing and passivation. It was found that instability of unanneald TFTs originates from creation of bulk defects, while that of an...

Supplementary Figures S1–S7

Here we demonstrate that water-infiltrated nanoporous glass electrically switches an oxide semiconductor from an insulator to metal. We fabricated the field effect transistor structure on an oxide semiconductor, SrTiO3, using 100%-water-infiltrated nanoporous glass - amorphous 12CaO*7Al2O3 - as the gate insulator. For positive gate voltage, electro...

Water is composed of two strong electrochemically active agents, H(+) and OH(-) ions, but has not been used as an active electronic material in oxide semiconductors. In this study, we demonstrate that water-infiltrated nanoporous glass electrically switches an oxide semiconductor from insulator to metal. We fabricated a field-effect transistor stru...

12CaO·7Al2O3 (C12A7) is an electrical insulator with a band gap ∼7.5eV. Contrary to conventional ultra-large gap oxides, electrical conductivity of C12A7 is controllable over a very wide range of 10−10 to 103Scm−1 by electron doping to a unique conduction band arising from 3-dimensionally connected sub-nanometer-sized cages constituting the crystal...

— Positive-current-bias (PB) instability and negative-bias—light-illumination (NBL) instability in amorphous-In—Ga—Zn—O (a-IGZO) thin-film transistors (TFTs) have been examined. The channel- thickness dependence indicated that the Vth instability caused by the PB stress is primarily attributed to defects in the bulk a-IGZO region for unannealed TFT...

The present status and recent research results on amorphous oxide semiconductors (AOSs) and their thin-film transistors (TFTs) are reviewed. AOSs represented by amorphous In–Ga–Zn–O (a-IGZO) are expected to be the channel material of TFTs in next-generation flat-panel displays because a-IGZO TFTs satisfy almost all the requirements for organic ligh...

Thin film transistors (TFTs) using polycrystalline tin oxides (SnO–SnO2) channels were formed on glass by a conventional sputtering method and subsequent annealing treatments. SnO-channel TFTs showed p-type operation with on/off current ratios of ∼ 102 and field-effect mobilities of 0.24 cm2 V−1 s−1. Incorporation of excess oxygen to SnO channel la...

A three-dimensional vertically-stacked flexible integrated circuit is demonstrated based on hybrid complementary inverters made of n -type In–Ga–Zn–O (a-IGZO) amorphous oxide thin-film transistors (TFTs) and p -type poly-(9,9-dioctylfluorene-co-bithiophene) (F8T2) polymer TFTs, where all the fabrication processes were performed at temperatures ≤120...

Amorphous In-Ga-Zn-O (a-IGZO) is expected for channel layers in thin-film transistors (TFTs). It is known that a-IGZO is sensitive to an O/H-containing atmosphere; therefore, it is important to clarify the roles of oxygen and hydrogen in a-IGZO. This paper provides atomic and electronic structures, formation energies of defects and bond energies in...

Amorphous In–Ga–Zn–O (α-IGZO) is expected for thin-film transistors (TFTs) in next-generation flat-panel displays but its intrinsic properties are not understood well and different mobility models have been applied to different films. This letter reports that a universal mobility model is obtained using a field-effect technique and capacitance-volt...

Amorphous oxide semiconductors (AOSs) are expected for alternative channel materials in thin-film transistors owing to their large electron mobilities. While, it is known that AOSs exhibit peculiar electron transport properties. Definite Hall voltages are observed even for mobilities < 0.2 cm(2)/V s, which correspond to a very short mean free path...

Stability under constant current stress, along with hysteresis characteristics, was studied for a-In-Ga-Zn-O thin-film transistors (TFTs) in several atmospheres and at several temperatures. Unannealed TFTs showed rather large instability; i.e., large hysteresis in transfer curves (ΔVG > 0.8 V) and large positive threshold voltage shift (ΔVth > 10 V...

A low-temperature process to improve performances of a-In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs) fabricated at room temperature was examined. Two deposition methods, pulsed laser deposition (PLD) and RF magnetron sputtering were employed to deposit the a-IGZO channels. For the PLD case, the TFT characteristics were improved significantly by...

Photoresponse was investigated for an amorphous oxide semiconductor, In–Ga–Zn–O, by the steady-state photoconductivity (SSPC) method. All the films exhibited extremely slow reversible photoresponses. Analysis of the transient photocurrent at varied temperatures provided similar activation energies of ~0.5eV for both the time constants and the photo...

Epitaxial (0001) films of GaN were grown on (111) YSZ substrates using single-crystalline InGaZnO4 (sc-IGZO) lattice-matched buffer layers by molecular beam epitaxy with a NH3 source. The epitaxial relationships are (0001)GaN//(0001)IGZO//(111)YSZ in out-of-plane and [112¯0]GaN//[112¯0]IGZO//[11¯0]YSZ in in-plane. This is different from those repor...

Atomically flat single-crystalline thin films of ScAlMgO4 (SCAM) were fabricated on yttria-stabilized zirconia (YSZ) (111) substrates by reactive solid-phase epitaxy using an ablation ceramic target with an optimized chemical composition. Owing to the good lattice matching, the SCAM layers enhanced two-dimensional growth of ZnO epitaxial films, sup...

We have measured the thermoelectric properties of layered Ca xCoO2 epitaxial films when the Ca-content was varied from x = 0.33 to 0.45. The Ca0.33CoO2 film, which was fabricated by ion-exchange of Na0.7CoO2 film, successfully incorporated the additional Ca-ions in-between the CoO2 layers by the thermal annealing with Ca(OH)2 powder. The thermal an...

Photoresponses of an amorphous oxide semiconductor, In-Ga-Zn-O (a-IGZO), are investigated by continuous-wave photocurrent measurements, which are discussed in terms of mobility-lifetime products (ν μ τ). It shows that a-IGZO has νμτ values larger than those of amorphous silicon, which originate from high Fermi levels as well as long photocarrier li...

Amorphous In–Ga–Zn-O (a-IGZO) thin-film transistors (TFTs) with a coplanar homojunction structure are demonstrated. The coplanar source and drain regions made of a-IGZO were formed by depositing a hydrogenated silicon nitride (SiNX:H) layer onto the a-IGZO layer. The a-IGZO regions on which the SiNX:H layer was directly deposited showed the low res...

Amorphous oxide semiconductors (AOSs) are expected as new channel materials in thin-film transistors (TFTs) for large-area and/or flexible flat-panel displays and other giant-microelectronics devices. So far, many prototype displays have been demonstrated in these four years since the first report of AOS TFT. The most prominent feature of AOS TFTs...

Electronic structures and carrier transport mechanisms in disordered oxide semiconductors, crystalline InGaO3(ZnO)m (m = 1,5) (c-IGZO)and amorphous InGaZnO4 (a-IGZO), are examined based on a percolation conduction model. Donor levels (Ed) and densities (ND) are estimated by numerical calculations of free electron densities (ne) obtained by Hall mea...

We report transistor characteristics and field-modulated thermopower (S) for single crystal SrTiO ₃ -based field-effect transistors (FETs). We use 150-nm-thick amorphous 12 CaO ∙7 Al ₂ O ₃ glass as the gate insulator of the SrTiO ₃ -FET. The resulting SrTiO ₃ -FET exhibits excellent transistor...

We grew epitaxial (110) Cu2O films on (110) MgO substrates toward high-mobility p-channel oxide thin-film transistors (TFTs). The (110) Cu2O films exhibited high Hall mobilities ∼90 cm2(Vs)−1 comparable to those of high-quality single-crystals, which were obtained in a narrow growth condition for 650 nm-thick films. TFTs using the epitaxial (110) C...

Tin monoxide (SnO) is a stable p-type oxide semiconductor. This paper reports electrical properties, electronic structures, and thin-film transistors (TFTs) of SnO. Epitaxial films were fabricated by pulsed laser deposition. The Hall mobility and the hole density of the epitaxial films were 2.4 cm2 V−1 s−1 and 2.5 × 1017, respectively. X-ray photoe...

Threshold voltage (V(th)) stability was examined under constant current stress for a-In-Ga-Zn-O thin film transistors (TFTs) deposited at room temperature and annealed at 400 degrees C in dry or wet O(2) atmospheres. All the TFTs exhibited positive V(th) shifts (Delta V(th)) and the Delta V(th) value was reduced by the thermal annealing to < 2 V fo...

Materials in In–Ga–Zn–O system are promising candidates for channel layers of high-performance thin-film transistors (TFTs). We investigated the atomic arrangements and the electronic structures of crystalline InGaZnO ₄ containing point defects such as oxygen vacancy (V_O) , interstitial hydrogen ( H _i) , and inter...

This paper discusses an optical model and subgap electronic states for a representative amorphous oxide semiconductor, InGaZnO4 (a-IGZO). Parameterized optical models were developed based on the Tauc–Lorentz model combined with a Lorentz-type oscillator. The measured optical absorption spectra exhibit nearly linear dependences on photon energy (E)...

We give general formulations of the multidimensional multicanonical algorithm, simulated tempering, and replica-exchange method.We generalize the original potential energy function E0 by adding any physical quantity V of interest as a new energy term. These multidimensional generalized-ensemble algorithms then perform a random walk not only in E0 s...

A fabrication process of coplanar homojunction thin-film transistors (TFTs) is proposed for amorphous In–Ga–Zn–O ( a -IGZO), which employs highly doped contact regions naturally formed by deposition of upper protection layers made of hydrogenated silicon nitride ( SiN _X: H ) . The direct deposition of SiN _X: H reduced the resi...

A homologous series compound ScAlO3(MgO) (SCAM) has a superior lattice matching as small as ∼1.4% in a-axis with GaN. This paper reports an efficient fabrication process of a single-crystalline SCAM buffer layer on a (111) yttria-stabilized zirconia (YSZ) substrate using pulsed laser deposition (PLD). A 10-nm thick ZnO epitaxial layer was used to i...

The electrical properties of Ca0.33CoO2 epitaxial films are investigated as the Ca2+-arrangement is transformed. Despite identical Ca-content, annealing the film caused the Ca-arrangement to change from a \sqrt{3}a×\sqrt{3}a hexagonal type to a 2a×\sqrt{3} a orthorhombic type, which was confirmed by X-ray diffraction and scanning transmission elect...

Amorphous oxide semiconductors (AOSs) are expected as new channel materials in thin-film transistors (TFTs) for large-area and/or flexible flat-panel displays and other giant-microelectronics devices. So far, many prototype displays have been demonstrated in these four years since the first report of AOS TFT. The most prominent feature of AOS TFTs...

We studied both the wavelength and intensity dependent photo‐responses (photofield‐effect) in amorphous In‐Ga‐Zn‐O (a‐IGZO) thin‐film transistors (TFTs). During the a‐IGZO TFT illumination with the wavelength range from 460∼660 nm (visible range), the off‐state drain current (IDS_off) only slightly increased while a large increase was observed for...

Cu2O epitaxial films were grown for high mobility p-channel oxide thin-film transistors (TFTs). The use of a (110) MgO surface and fine tuning of a growth condition produced single phase epitaxial films with hole Hall mobilities ∼ 90 cm2 V−1 s−1 comparable to those of single crystals ( ∼ 100 cm2 V−1 s−1). TFTs using the epitaxial film channels exhi...

Roles of H2O addition to an annealing atmosphere were investigated for amorphous In–Ga–Zn–O thin-film transistors fabricated at room temperature. Although dry O2 annealing improved saturation mobility (μsat) and subthreshold voltage swings (S), wet O2 annealing further improved them to μsat ∼ 12 cm2(V s)−1 and S<0.12 V decade−1 along with improveme...

This paper reviews recent progress in AOSs TFT technology and science. The origins of the low voltage operation and the large mobility are discussed in relation with subgap density of states and the density functional theory.

This paper reports that among known p -type oxide semiconductors, tin monoxide (SnO) has a high hole mobility and produces good p -type oxide thin-film transistors (TFTs). Device-quality SnO films were grown epitaxially on (001) yttria-stabilized zirconia substrates at 575 ° C by pulsed laser deposition. These exhibited a Hall mobility of 2.4 cm <s...

Electronic structures and carrier transport properties were studied based on ab-initio calculations for Au/ZnO/Au and Mg/ZnO/Mg two-probe models. Quantum-mechanically stable structures were obtained by density functional calculations. Electron transmission spectra and current–voltage characteristics were calculated based on a non-equilibrium Green...

The compositional dependence of sputter-deposited Zn–In–O (ZIO) film properties and the TFT performance were studied by means of a combinatorial technique. Both the characteristics of ZIO-TFTs and the ZIO film properties are very sensitive to the Zn:In ratio. The best TFT performances are obtained at Zn:In ∼60:40 at%, where the saturation mobility...

Electron-doped 12CaO·7Al2O3 (C12A7) nanowires (NWs) were fabricated by two approaches. First, spatially selective electron doping of C12A7 films was examined by using a chemical method specific to C12A7. However, the conductive NW was not formed due to diffusion of oxygen in the C12A7 films to the conductive area. Secondly, a combination of dry etc...

The relationship between non-localized tail states and carrier transport in transparent amorphous oxide semiconductor, In–Ga–Zn–O (a-IGZO), was investigated. It was found that the energy width (E0) of the non-localized tail states varied from <7 meV to 20 meV depending on the film deposition conditions (i.e. film quality). At carrier concentrations...

Transparent amorphous oxide semiconductors (TAOS) such as a-InGaZnO4 are expected to be applied for channels of low-temperature high-mobility thin-film transistors (TFTs). This paper presents the fabrication and characteristics of amorphous Sn–Ga–Zn–O (a-SGZO) channel TFTs. Bottom-gate TFTs were fabricated using as-deposited and annealed a-SGZO cha...