Hidejiro Miki

Control of electrical conductivity in laser deposited SrTiO3 thin films with Nb doping

Nb‐doped SrTiO3 (STO) thin films (Nb, 0<x<100 mol%) with a‐axis orientation have been prepared on nondoped STO (100) and LaAlO3 (100) single crystals using a pulsed laser deposition technique. Solid‐solution films are formed between STO and SrNbO3 without any impurity phases. Electrical conductivities of Nb‐doped STO films can be controlled from 10−7 to 104 S/cm by changing the concentration of the doped Nb. Carrier concentration of the Nb‐doped STO films also increases by increasing the Nb concentration.

Atomic-layer chemical-vapor-deposition of silicon dioxide films with an extremely low hydrogen content

We achieved the atomic-layer-deposition of SiO2 with an extremely low H content for the first time by using Si(NCO)4 and N(C2H5)3. The deposition rate was independent of the exposure times of both sources. The saturated deposition rate was about 1.2 A/cycle at 150°C. AFM observation revealed that the increase of roughness after 50 deposition cycles was only about 0.4 A in root mean square. The FT-IR spectra showed that the deposited film was SiO2 without Si–H, Si–OH or NCO bond.

Characteristics of Hydrogenated Amorphous Silicon Films Prepared by Electron Cyclotron Resonance Microwave Plasma Chemical Vapor Deposition Method and Their Application to Photodiodes

The electron cyclotron resonance microwave plasma chemical vapor deposition (ECRPCVD) method has been applied to prepare a-Si:H films. A high deposition rate of 136 nm/min was achieved. Even without substrate heating and with the high deposition rate, a-Si:H films prepared by ECRPCVD have sufficient characteristics, as follows: the dark conductivity is 3-4×10-10S/cm, ηµτ is 4.2×10-5cm2/V and the optical band-gap is 1.81 eV. Furthermore, the electric characteristics are somewhat improved with substrate heating. Hydrogenated amorphous silicon films prepared by ECRPCVD without substrate heating and with a high deposition rate of 136 nm/min have been applied to ITO/a-Si:H/Cr Schottky-barrier photodiodes. These photodiodes have sufficient characteristics to be applied to image sensors for a facsimile reader and other systems.

Degradation of Gallium Arsenide Crystals by the Cold-Working Treatment (Abrasion)

The effect of the cold working treatment on the characteristics of GaAs crystals was studied. Abrasion and subsequent heat treatment of the crystals decrease the carrier concentrations and increase the breakdown voltages. After abrading and subsequent heat treatment, the increase in etch-pit density in the crystals was observed. It is supposed that the degradation of the crystals was related to the generation of dislocations during such treatments.

The Influence of Oxygen on the Properties of GaAs Grown by Liquid Phase Epitaxy

Epitaxial layers of GaAs are grown from Ga solution. The effects of oxygen in achieving high purity GaAs layers are investigated. From the experimental results of doping with Ga2O3, the growth temperature dependence of carrier concentration and the impurity profile are explained by the temperature dependence of the distribution coefficient of oxygen in GaAs grown by liquid phase epitaxy. The distribution coefficients of oxygen are 6.5×10-4 at 700°C, 1.8×10-4 at 750°C and 5.1×10-5 at 800°C, respectively.

Photoluminescence Study of Defects in GaAs Formed by Annealing in an H2 Gas Flow

GaAs crystals were annealed in an H2 gas flow and the degraded layer formed on the surface by annealing has been investigated by a photoluminescence measurement. The origin of the defects, in particular an emission at 890 nm, formed by annealing has also been investigated with the aid of the liquid phase epitaxy technique. The degradation of the surface is governed by self-diffusion of As vacancies. The degraded layer depth increases in proportion to the square root of the heating time, whose rate depends on carrier concentrations in the crystals. As the crystals are annealed in an H2 gas flow, new emission band at 890 nm grows drastically. It is concluded that the band is due to electron transitions from a shallow donor to an As vacancy acceptor.

Electrical and optical properties of boron and nitrogen implanted In2O3 thin films

Abstract Electrical and optical properties of In2O3 thin films doped with boron and nitrogen have been studied. Boron and nitrogen ions were implanted into In2O3 thin films with an energy of 25 and 35 keV, respectively, at doses of 1×10 15 –1.6×10 16 cm −2 . After implantation the films were annealed for 1 h in air and subsequently for 1 h in a vacuum. After the two-step annealing at 350°C, the electrical resistivity of the boron implanted sample with a dose of 4×10 15 cm −2 achieved 4.4×10 −4 Ω cm with an averaged optical transmittance of 84% at a wavelength between 380 and 780 nm. On the other hand, for nitrogen implanted samples, the resistivity did not improve by ion implantation but the optical transmittance was unchanged.

The Ga–In–Sb Ternary Phase Diagram at Low Growth Temperature

The ternary phase diagram of the Ga–In–Sb system was investigated. The solidus isotherm at 400°C and liquidus isotherms at 400, 500, and 600°C were determined experimentally. The phase diagram of Ga–In–Sb system was calculated on the basis of various thermodynamic parameters. It is found that the calculation with the modified Delta Lattice Parameter (DLP) model best fits the experimental solidus isotherm at 400°C.

Electrical and optical properties of carbon implanted In2O3 thin film

Abstract Electrical and optical properties of In2O3 thin film with carbon ion implantation have been studied. The location of the implanted carbon in the film was also investigated by means of a high-resolution electron microscope. Carbon ions were implanted into In2O3 thin films with an energy of 30 keV at doses of 1×1015 to 2×10 16 cm −2 . After implantation the films were annealed for 1 h in air and subsequently for 1 h in a vacuum. After the two step annealing at 350°C, the electrical resistivity achieved for a sample with an ion dose of 5×10 15 cm −2 was 5.4×10−4 Ω cm with an optical transmittance of 82% at a wavelength of 550 nm.

Low-Resistivity Highly Transparent Indium-Tin-Oxide Thin Films Prepared at Room Temperature by Synchrotron Radiation Ablation

High-transparency, low-electrical-resistivity indium-tin-oxide (ITO)thin films were prepared on quartz substrates using synchrotron radiation ablation at room temperature. The films had a low resistivity (ρ=1.3×10-4 Ωcm) and high-transparency properties in the visible region (T = 83% at 550 nm). X-ray diffraction patterns indicate that the crystalline ITO film was obtained by room-temperature deposition.