There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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. ...

/pdf/a-comprehensive-review-of-zno-materials-and-devices-21a3zjadem.pdf

A comprehensive review of zno materials and devices

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.

Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors

We report that a layered iron-based compound LaOFeAs undergoes superconducting transition under doping with F- ions at the O2- site. The transition temperature (Tc) exhibits a trapezoid shape dependence on the F- content, with the highest Tc of ∼26 K at ∼11 atom %.

Iron-Based Layered Superconductor La[O1-xFx]FeAs (x = 0.05−0.12) with Tc = 26 K

We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Band parameters for III–V compound semiconductors and their alloys

Humidity-Sensitive Electrical Conductivity in 12CaO7Al2O3 Derivatives Crystal

We report the first electronic conduction in main group metal oxides (MGOs) or light-metal oxides, which are represented by alkaline-earth oxides, alumina, and silica. They are believed to be never converted to an electronic conductor. One of the MGOs, 12CaO·7Al2O3 (C12A7), has optical transparency, but electrical insulation limits intrinsic form. It is characterized by sub-nanometer sized cages in the lattice framework. Hydride ion, H- was incorporated into the cage by a thermal treatment of C12A7 single crystals or ceramics in hydrogen atmosphere. The product, C12A7:H, was colorless, transparent and a good insulator having electronic conductivity less than 10-10 S·cm-1. We found that the C12A7:H exhibits a coloration of yellowish green corresponding to optical absorptions at 2.8 and 0.4 eV with simultaneous conversion into an electronic conductor with 0.3 S·cm-1 at 300 K upon a irradiation of ultraviolet light. The conductive state continued even after the irradiation was stopped. Inversion to the insulator occurred when heated more than ∼320°C accompanying with rapid decay of the optical absorptions. When temperature rose above 550°C, H2 gas was released from the sample and the photosensitivity was lost. We consider that high concentration of F +-like centers are created by photo-released electrons from the H- anions being captured by empty cages. Further, a migration of the electrons at the F +-like centers may be responsible for the conduction. The visible light absorption loss is estimated to be only 1% for a 200 nm thick conductive C12A7:H films. The present properties provides novel applications such as direct optical writing of conducting wires on insulating transparent media.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400155885

Photo-Induced Insulator-Semiconductor Transition in 12CaO·7Al2O3 (C12A7)

https://iopscience.iop.org/article/10.1143/JJAP.45.L512/pdf

Erratum: ?Bipolar Room Temperature Ferromagnetic Semiconductor LaMnOP?

We confirmed that quantum confinement effects are clearly observed even in a disordered material. Employing amorphous In–Ga–Zn–O ( a-IGZO) thin-film transistors (TFTs) with quantum well channels, it was observed that field-effect mobility–gate voltage relations exhibited plateaus when the well thickness was 5 nm or less. Device simulation incorporating the quantum confinement effects reproduced the well-thickness dependence of the plateau onset voltage, verifying that the quantized electronic levels in the a-IGZO well dominate the TFT characteristics and, thus, the electron transport is free electron like with a coherent length of ∼5 nm. The field-effect mobility did not exceed the drift mobility of bulk a-IGZO, which is different from amorphous silicon superlattice TFT.

Quantum confinement effects in amorphous In–Ga–Zn–O thin-film transistors with quantum well channel

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 whereas it recover the initial one with a small threshold voltage and a large subthreshold swing upon light illumination. Therefore, these a-IGZO TFTs can be used as light irradiation history sensors; first, the gate voltage is applied to initialize the Ids-Vgs characteristic, next, the light is irradiated and finally, the Ids-Vgs characteristic is measured which depends on the light irradiation history. Moreover, these a-IGZO TFTs can be also used as applied voltage history sensors; first, the light is irradiated to initialize the Ids-Vgs characteristic, next, the gate voltage is applied and finally, the Ids-Vgs characteristic is measured which depends on the value or time of the applied voltage.

Light irradiation and applied voltage history sensors using amorphous In-Ga-Zn-O thin-film transistors exposed to ozone annealing and fabricated under high oxygen pressure

Toshio Kamiya

Papers

Humidity-Sensitive Electrical Conductivity in 12CaO7Al2O3 Derivatives Crystal

Photo-Induced Insulator-Semiconductor Transition in 12CaO·7Al2O3 (C12A7)

Erratum: ?Bipolar Room Temperature Ferromagnetic Semiconductor LaMnOP?

Quantum confinement effects in amorphous In–Ga–Zn–O thin-film transistors with quantum well channel

Light irradiation and applied voltage history sensors using amorphous In-Ga-Zn-O thin-film transistors exposed to ozone annealing and fabricated under high oxygen pressure