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

We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO 3 (ZnO) 5 , as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of ∼10 6 and a field-effect mobility of ∼80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics.

http://science.sciencemag.org/content/sci/300/5623/1269.full.pdf

Thin-Film Transistor Fabricated in Single-Crystalline Transparent Oxide Semiconductor

Recent progress in processing and properties of ZnO

https://iopscience.iop.org/article/10.1088/1468-6996/11/4/044305/pdf

Present status of amorphous In–Ga–Zn–O thin-film transistors

Highly transparent ZnO-based thin-film transistors (TFTs) are fabricated with optical transmission (including substrate) of ∼75% in the visible portion of the electromagnetic spectrum. Current–voltage measurements indicate n-channel, enhancement-mode TFT operation with excellent drain current saturation and a drain current on-to-off ratio of ∼107. Threshold voltages and channel mobilities of devices fabricated to date range from ∼10 to 20 V and ∼0.3 to 2.5 cm2/V s, respectively. Exposure to ambient light has little to no observable effect on the drain current. In contrast, exposure to intense ultraviolet radiation results in persistent photoconductivity, associated with the creation of electron-hole pairs by ultraviolet photons with energies greater than the ZnO band gap. Light sensitivity is reduced by decreasing the ZnO channel layer thickness. One attractive application for transparent TFTs involves their use as select-transistors in each pixel of an active-matrix liquid-crystal display.

/pdf/zno-based-transparent-thin-film-transistors-4ep6ghphpx.pdf

ZnO-based transparent thin-film transistors

An ultraviolet light-emitting diode (LED) operating at room temperature was realized using a p–n heterojunction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO. Multilayered films prepared by a pulsed-laser deposition technique were processed by conventional photolithography with the aid of reactive ion etching to fabricate the LED device. A rather sharp emission band centered at 382 nm was generated when a forward bias voltage exceeding the turn-on voltage of 3 V was applied to the junction. The emission may be attributed to a transition associated with the electron–hole plasma of ZnO.

Current injection emission from a transparent p–n junction composed of p-SrCu2O2/n-ZnO

Oxidation behavior of Fe–16Cr alloy interconnect for SOFC under hydrogen potential gradient

${\mathrm{GeO}}_{2\mathrm{\ensuremath{-}}}$${\mathrm{SiO}}_{2}$ glasses prepared by vapor-phase axial deposition were exposed to ultraviolet (uv) radiation from a Hg discharge lamp (4.9 eV) and excimer lasers (KrF laser: 5.0 eV, XeCl laser: 4.0 eV). Two photochemical reaction channels were ascertained: (1) The exposure of the glasses to the Hg lamp radiation (\ensuremath{\sim}16 mW/${\mathrm{cm}}^{2}$) induced Ge E' centers accompanied by bleaching of the absorption band due to oxygen-deficient defects near 5 eV (5-eV band) and the emergence of an intense band near 6.4 eV. (2) The irradiation with KrF and XeCl lasers (power densities of 10 and 90 mJ/${\mathrm{cm}}^{2}$/pulse, respectively, pulse duration of 20 ns) generated two types of paramagnetic defects, electron trapped centers associated with fourfold coordinated Ge ions (GEC) and a self-trapped hole center (STH: bridging oxygen trapping a hole). The former and the latter were considered to be caused via one-photon and two-photon absorption processes, respectively. These alternative reactions proceeded independently depending on the power densities of uv photons. The formation of GEC's was saturated easily by irradiation with KrF laser pulses, and then the conversion of GEC to Ge E' centers was caused by prolonged irradiation.

Photochemical reactions in GeO2-SiO2 glasses induced by ultraviolet irradiation: Comparison between Hg lamp and excimer laser.

Fabrication of surface relief-type gratings in transparent dielectrics, which are hard to machine, has been achieved by a holographic technique using two infrared femtosecond (fs) pulses from a mode-locked Ti:sapphire laser. The present method can be applied for a variety of transparent dielectrics, Al2O3 (sapphire), TiO2, ZrO2, LiNbO3, SiC, ZnO, CdF2, MgO, CaF2 crystals, and SiO2 glass. It is found that the grating formation is due primarily to laser ablation processes. Planar surface relief gratings can be fabricated by colliding two fs laser pulses on the surface of substrates which move at a constant speed, synchronized with the laser repetition rate.

Kenichi Kawamura

Papers

Current injection emission from a transparent p–n junction composed of p-SrCu2O2/n-ZnO

Oxidation behavior of Fe–16Cr alloy interconnect for SOFC under hydrogen potential gradient

Photochemical reactions in GeO2-SiO2 glasses induced by ultraviolet irradiation: Comparison between Hg lamp and excimer laser.

Fabrication of surface relief gratings on transparent dielectric materials by two-beam holographic method using infrared femtosecond laser pulses

Lattice expansion upon reduction of perovskite-type LaMnO3 with oxygen-deficit nonstoichiometry