Shinya Ohmagari 교수

Dislocations in semiconductor crystals are desirably minimized as much as possible, since their presence typically deteriorates device performance. While diamond electronics have demonstrated superior device properties, they have not fulfilled their material limit yet. To further improve device performance, a low dislocation density and a high-quality epitaxial layer are required. In this study, diamond films are homoepitaxially grown by hot-filament chemical vapor deposition accompanying W inco

Reverse characteristics of vertical-type Au/p-diamond (100) Schottky barrier diodes were investigated and characterized with cathodoluminescence, which showed a correlation with crystalline defects. Electrical measurements revealed that most diodes had low reverse current below 0.1 pA in the bias voltage range up to 50 V, although reverse current increases rapidly in some diodes and reaches 0.1 mA at 10 V. A four-fold symmetrical luminescence pattern that aligned crystallographically to the subs

p-Type ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films were fabricated by pulsed laser deposition using boron-doped graphite targets. Thermal analysis confirmed the occurrence of p-type conduction. The electrical conductivity increased with the doped amount of boron. An activation energy estimated from the Arrhenius plot was approximately 0.1 eV. Near-edge X-ray absorption fine structure spectra revealed that the σ * C–H peak weakened and the σ * C–B pea

The atomic bonding configuration of ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a‐C:H) films prepared by pulsed laser ablation of graphite in a hydrogen atmosphere was examined by near‐edge X‐ray absorption fine structure spectroscopy. The measured spectra were decomposed with simple component spectra, and they were analyzed in detail. As compared to the a‐C:H films deposited at room substrate‐temperature, the UNCD/a‐C:H and nonhydrogenated amorphous carbon (a‐C) films dep

Diamond mosaic wafers in which several seed crystals are connected laterally by chemical vapor deposition (CVD) are promising large-scale substrates for diamond electronics. One of the prime concerns of the applicability of diamond mosaic wafers is the presence of highly defective coalescence boundaries, which degrade the electrical performance. For Schottky barrier diodes (SBDs), a large leakage current with an inferior Schottky barrier height has been observed at mosaic boundaries. To further

A major obstacle limiting diamond electronics is dislocations, which deteriorate device properties. As threading dislocations (TDs) are normally inherited from the substrate to the epitaxial layer, control and annihilation of their propagation are important. Herein, metal‐assisted termination (MAT), in which the propagation of dislocations is suppressed by in situ metal doping, is proposed. Heavy W doping is realized by a hot‐filament (HF) chemical vapor deposition (CVD) using heated wires at a

Deep-ultraviolet (DUV) light detection of p-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films prepared by pulsed laser deposition was investigated. The photocurrent spectra revealed that the UNCD/a-C:H films possess strong responses in the wavelength range between 210 and 280 nm, which might originate from UNCD grains. The heterojunction photodiodes comprised of p-type UNCD/a-C:H and n-type Si exhibited an obvious photovoltaic action for 254 nm DUV ligh

Diamond single crystals have garnered significant attention due to their wide-ranging applications, encompassing not only semiconducting films but also potential quantum sensing materials. The hot-filament activated chemical vapor deposition (HFCVD) technique has been extensively employed to produce polycrystalline diamond films, hard coatings, boron-doped diamond electrodes, and thermal management applications, primarily due to its notable advantages in scalability (>12 inches). However, the gr

We fabricated diamond pseudo-vertical Schottky barrier diodes using a half-inch semi-insulative diamond (100) wafer. Most diodes exhibited a large rectifying ratio (>1010) with undetectable leakage current at a reverse bias of 5 V (0.6 MV cm−1), with only 2% of diodes exhibiting an Ohmic-like leakage current. Surface defects were observed under the Schottky barrier diode, and their impacts on electrical properties were analyzed using a Murphy model and correlation factor analysis. We foun