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. ...

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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

Relatively nontoxic, earth-abundant Cl was incorporated into n-type SnS as a dopant. The existence of impurity phases was carefully identified in Sn(S1− x − y Cl x )-dense ceramics. The highest electron mobility (8.3 cm2 V−1 s−1) in n-type conduction was achieved in samples with x ≥ 0.005. Cl concentration is critical for conduction-type conversion, whereas carrier density and electron mobility are determined by sulfur-site deficiency. Carrier transport is explained by grain boundary potential barrier scattering in undoped p-type samples and by ionized impurity scattering in Cl-doped n-type samples.

https://iopscience.iop.org/article/10.7567/APEX.9.051201/pdf

N-type conduction in SnS by anion substitution with Cl

Fabrication and electron transport properties of epitaxial films of electron-doped 12CaO·7Al2O3 and 12SrO·7Al2O3

KFe2As2, an iron-based superconductor, is expected to exhibit large spin Hall conductivity, and fabrication of high-quality thin films is requisite for evaluation of this effect and application to spintronics devices. Thin-film growth of KFe2As2 is difficult because of two intrinsic properties; its extremely hygroscopic nature and the high vapor pressure of potassium. We solved these issues by combining room-temperature pulsed laser deposition using K-rich KFe2As2 targets with thermal crystallization in KFe2As2 powder after encapsulation in an evacuated silica-glass tube with all of the processes conducted in a vacuum chamber and a dry Ar atmosphere in a glovebox. The optimized KFe2As2 films on (La,Sr)(Al,Ta)O3 single-crystal substrates were obtained by crystallization at 700 °C, and they were strongly c-axis oriented. The electrical measurements were performed with thin films protected by grease passivation to block reaction with the atmosphere. The KFe2As2 films exhibited a superconductivity transition ...

Growth of c-Axis-Oriented Superconducting KFe2As2 Thin Films

YCuOSe was prepared by solid-state reaction, and its wide gap semiconducting properties were examined. The single phase of YCuOSe was obtained in a limited temperature range around 750°C and decomposed into Y2O2Se and Cu2Se at higher temperatures. The obtained YCuOSe sample showed a p-type semiconducting behavior with the electrical conductivity of 1.4×10−1Scm−1 at room temperature. The band gap of YCuOSe was estimated to be 2.58eV, which is much smaller than that of LaCuOSe (2.82eV). The electronic structure of YCuOSe was investigated by ultraviolet photoemission spectroscopy and energy band calculations to understand the differences in the electronic structures between LnCuOSe (Ln=La,Y). It was found that the Cu–Cu distance rather than the Cu–Se distance influences the electronic structures, and the smaller band gap of YCuOSe is attributed to the downshift of the Cu 4s energy level due to the smaller Cu–Cu distance and the consequent larger Cu–Cu interaction in YCuOSe.

Optoelectronic properties and electronic structure of YCuOSe

Polycrystalline SnS thin films were fabricated by a H2S-free process combing pulsed laser deposition at room temperature and post-deposition thermal annealing in Ar. Thermal annealing improved the crystalline quality of the SnS films and the best films were obtained by 400 °C annealing. The obtained SnS films exhibited p-type conduction with the highest Hall mobility of 28 cm2/(V ⋅ s) and the carrier densities of 1.5 × 1015 – 1.8 × 1016 cm−3. The SnS TFT exhibited p-type operation with a field effect mobility and an on-off drain current ratio of 0.4 cm2/(V ⋅ s) and 20, respectively.

Toshio Kamiya

Papers

N-type conduction in SnS by anion substitution with Cl

Fabrication and electron transport properties of epitaxial films of electron-doped 12CaO·7Al2O3 and 12SrO·7Al2O3

Growth of c-Axis-Oriented Superconducting KFe2As2 Thin Films

Optoelectronic properties and electronic structure of YCuOSe

SnS thin films prepared by H2S-free process and its p-type thin film transistor