The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

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A comprehensive review of zno materials and devices

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.

Oxide Semiconductor Thin‐Film Transistors: A Review of Recent Advances

Recent progress in processing and properties of ZnO

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

A method for forming a conductive material on a substrate includes laser annealing a selected portion of a blanket coated material to form a conductive region.

System and method for forming conductive material on a substrate

Molecular beam epitaxial growth of wide bandgap ZnMgO alloy films on (111)-oriented si substrate toward UV-detector applications

The authors propose a new structure of ZnO∕ZnMgO field-effect transistors (FETs) for demonstrating high-performance capability of ZnO-based FETs. A very thin (2nm) ZnMgO cap layer is used for forming a hetero-metal-insulator-semiconductor (hetero-MIS) gate structure together with a 50-nm-thick Al2O3 gate dielectric. The 1-μm-gate device showed a complete FET operation and an extrinsic transconductance of as high as 28mS∕mm and an effective mobility of 62cm2∕Vs. The high effective mobility maintained down to such a short channel device is likely due to the use of the hetero-MIS structure, demonstrating the high-performance capability of ZnO-based FETs.

High-performance ZnO∕ZnMgO field-effect transistors using a hetero-metal-insulator-semiconductor structure

Characterization of a Zn0.7Mg0.3O∕ZnO heterostructure field-effect transistor (HFET) is reported. The HFET was based on a Zn0.7Mg0.3O∕ZnO∕Zn0.7Mg0.3O single quantum well (SQW) grown on an a-plane sapphire substrate by molecular-beam epitaxy, and was fabricated by a conventional photolithography technique combined with dry etching. Room-temperature characteristic of the HFET was a n-channel depletion type with a transconductance of 0.70mS∕mm and a field-effect mobility of 140cm2∕Vs, in good agreement with the electron Hall mobility in SQW of 130cm2∕Vs. The on∕off ratio at VDS=3V was ∼800, which was limited by an insufficiently suppressed leakage current through the bottom Zn0.7Mg0.3O barrier.

Characteristics of a Zn0.7Mg0.3O∕ZnO heterostructure field-effect transistor grown on sapphire substrate by molecular-beam epitaxy

A concept for the fabrication of highly symmetric quantum dots that are coherently embedded in a single crystalline matrix is demonstrated. In this approach, the formation of the quantum dots is induced by a transformation of an epitaxial two dimensional quantum well into an array of isolated precipitates with dimensions of about 25nm. The formation process is driven by the immiscibility of the constituent materials resulting from their different lattice structures. The investigated PbTe∕CdTe heterosystem combines two different cubic lattices with almost identical lattice constants. Therefore, the precipitated quantum dots are almost strain-free and near thermodynamic equilibrium they exhibit the shape of small-rhombo-cubo-octahedrons. The PbTe∕CdTe quantum dots, grown on GaAs substrates, display intense room temperature luminescence at wavelength of around 3.2μm, which makes them auspicious for applications in midinfrared photonic devices.

Kazuto Koike

Papers

Molecular beam epitaxial growth of wide bandgap ZnMgO alloy films on (111)-oriented si substrate toward UV-detector applications

High-performance ZnO∕ZnMgO field-effect transistors using a hetero-metal-insulator-semiconductor structure

Characteristics of a Zn0.7Mg0.3O∕ZnO heterostructure field-effect transistor grown on sapphire substrate by molecular-beam epitaxy

Centrosymmetric PbTe∕CdTe quantum dots coherently embedded by epitaxial precipitation

ZnO and ZnMgO growth on a-plane sapphire by molecular beam epitaxy