Modeling of grain boundary barrier modulation in ZnO invisible thin film transistors

Hossain, Faruque M.; Nishii, Junya; Takagi, S.; Sugihara, Tadashi; Ohtomo, Akira; Fukumura, Tomoteru; Koinuma, Hideomi; Ohno, Hideo; Kawasaki, Masashi

doi:10.1016/j.physe.2003.11.149

Cited by 73 publications

(48 citation statements)

References 4 publications

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“…Recent simulation of a model of polycrystalline ZnO TFT [8] suggested that a double Schottky-like potential barrier would develop at grain boundaries and act as a charge valve in response to the gate bias. In this model, l FE was shown to increase supralinearly on increasing the gate bias, [9] and this has actually been observed in the devices. It is necessary to use a robust dielectric material for the gate, in order to lower the interface trap density.…”

supporting

confidence: 53%

Hall and Field‐Effect Mobilities of Electrons Accumulated at a Lattice‐Matched ZnO/ScAlMgO₄ Heterointerface

Suzuki

Ohtomo²,

Tsukazaki

et al. 2004

Advanced Materials

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Recent research into field-effect transistors (FETs) has often involved investigation of materials that could be used as alternatives to silicon, so that additional device functionalities that cannot be attained using silicone-based FETs can be realized. Transparent electronics, based on wide-bandgap semiconductors and flexible, large-area electronics consisting of organic semiconductors are currently subjects of intensive materials research. From a practical perspective, ZnO is a most attractive wide-bandgap semiconductor because of its low processing temperatures and low cost. Production of thinfilm transistors (TFTs) based on polycrystalline ZnO channels have been reported by several groups, [1±7] among whose works include the demonstration of a fully transparent device.[4] The field-effect mobilities (l FE ) reported in those studies, however, were quite low (0.01±7 cm 2 V ±1 s ±1). Recent simulation of a model of polycrystalline ZnO TFT [8] suggested that a double Schottky-like potential barrier would develop at grain boundaries and act as a charge valve in response to the gate bias. In this model, l FE was shown to increase supralinearly on increasing the gate bias, [9] and this has actually been observed in the devices. It is necessary to use a robust dielectric material for the gate, in order to lower the interface trap density. Such a material has not yet been established, but a CaHfO 3 buffer layer placed underneath the channel has been successfully used.[1] Considering these obstacles to realizing polycrystalline ZnO transistors with high mobility, it should be appropriate to investigate the field-effect characteristics of FETs that are made from single-crystalline ZnO films with well-defined dielectric gates. A grain-boundary-free channel should make it possible to achieve values of l FE that are comparable to those in the bulk crystal, and to realize intrinsic field-effect characteristics.Here we report on the simultaneously measured field-effect transfer characteristics and Hall-effect properties of a latticematched ZnO/ScAlMgO 4 (ZnO/SCAM) [10] heteroepitaxial interface, using an electric field applied through the SCAM substrate, which acted as the gate dielectric. We have previously reported that this particular heterostructure is outstanding in its ability to regulate the epitaxial processes in layer-by-layer growth, [11] and that excellent exciton-related optical properties can be realized in the ZnO epitaxial films formed. [12] We have successfully accumulated electrons with a density of up to~1 10 13 cm ±2 by reducing the SCAM thickness to 10 lm and applying a gate voltage of up to 1 kV (i.e., an electric field of up to 1 MV cm ±1 ). The dependence of the field-effect, Hall, and conductance mobilities on the gate voltage are discussed in order to evaluate the intrinsic field-effect transfer characteristics of the single-crystalline ZnO film, and to compare these properties with those observed in polycrystalline devices. The field-effect mobilities in the present devices can be as high as~70 c...

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supporting

confidence: 53%

Hall and Field‐Effect Mobilities of Electrons Accumulated at a Lattice‐Matched ZnO/ScAlMgO₄ Heterointerface

Suzuki

Ohtomo²,

Tsukazaki

et al. 2004

Advanced Materials

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“…In the absence of grain boundaries, drain current is influenced by the interface state density, the electron mobility, and the impurity levels in the crystal. For nc-ZnO TFTs, the additional influence of the potential barriers at the grain boundaries must be included [27][28][29][30]. The drain current is therefore a sensitive device parameter that can be used to assess the quality of nc-ZnO thin films.…”

Section: Thin Film Transistorsmentioning

confidence: 99%

Self-assembled nanocrystalline ZnO thin film transistor performance optimization for high speed applications

Bayraktaroglu¹,

Leedy²

2014

Turk J Phys

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Abstract:ZnO nanocrystals grown at relatively low temperatures using various vacuum deposition techniques can yield semiconducting thin films of self-assembled nanocolumns 20-50 nm in diameter. Such films are suitable for the fabrication of high speed and transparent thin film transistors (TFTs). Unlike amorphous TFTs, the performance of ZnO transistors depends both on the crystal quality of nanocrystals and the electrical properties of boundary layers between them. We investigated the use of radio frequency sputtering, atomic layer deposition, and pulsed laser deposition techniques to fabricate self-assembled nanocrystalline thin films and determined the influence of deposition conditions on the performance of transistors. Device design and fabrication parameters were also optimized to demonstrate TFTs with high current density and high speed performance comparable to single crystalline-based transistors.

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“…142,143 The Nature Mater JJAP LED B Figure 14. Three generations of electroluminescence spectra from ZnO-based light-emitting devices.…”

Section: ¹3mentioning

confidence: 99%

Exploration of Electronic Functionalities in Metal Oxides by Combinatorial Lattice Engineering

Kawasaki

2013

Bulletin of the Chemical Society of Japan

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A review is given for our originally-developed thin film technology, "combinatorial lattice engineering." This is extended from a conventional pulsed laser deposition, where the surface of a sintered oxide tablet (target) is irradiated with focused laser pulses and the evaporated precursors are condensed on a heated substrate to grow single crystalline thin films. By this method, it has become possible to concurrently synthesize many oxide thin films on a substrate at different locations (segments) with such diversities as composition, growth conditions, and the sequence of heterostructures. By inserting a masking system between the target and substrate and computer controlling the mask motion as well as target switching, one can integrate many oxide thin film segments on the substrate. Starting from the background of and demand for this technology as well as the advancement of the key ingredient technology, i.e., atomically regulated epitaxial growth of oxide thin films, the concept and examples of this combinatorial lattice engineering are introduced highlighting the representative demonstration on magnetic, photonic, and electronic functionalities, especially emphasizing the benefit of this combinatorial technology. In addition, further progress of device physics triggered by the combinatorial discoveries are introduced, for example, electric field control of magnetism, bright ultraviolet light emitting devices, and quantum effects in oxide semiconductors.

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Modeling of grain boundary barrier modulation in ZnO invisible thin film transistors

Cited by 73 publications

References 4 publications

Hall and Field‐Effect Mobilities of Electrons Accumulated at a Lattice‐Matched ZnO/ScAlMgO₄ Heterointerface

Hall and Field‐Effect Mobilities of Electrons Accumulated at a Lattice‐Matched ZnO/ScAlMgO₄ Heterointerface

Self-assembled nanocrystalline ZnO thin film transistor performance optimization for high speed applications

Exploration of Electronic Functionalities in Metal Oxides by Combinatorial Lattice Engineering

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Modeling of grain boundary barrier modulation in ZnO invisible thin film transistors

Cited by 73 publications

References 4 publications

Hall and Field‐Effect Mobilities of Electrons Accumulated at a Lattice‐Matched ZnO/ScAlMgO4 Heterointerface

Hall and Field‐Effect Mobilities of Electrons Accumulated at a Lattice‐Matched ZnO/ScAlMgO4 Heterointerface

Self-assembled nanocrystalline ZnO thin film transistor performance optimization for high speed applications

Exploration of Electronic Functionalities in Metal Oxides by Combinatorial Lattice Engineering

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Product

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Hall and Field‐Effect Mobilities of Electrons Accumulated at a Lattice‐Matched ZnO/ScAlMgO₄ Heterointerface

Hall and Field‐Effect Mobilities of Electrons Accumulated at a Lattice‐Matched ZnO/ScAlMgO₄ Heterointerface