The successful development of silicon carbide (SiC) semiconductor technology requires a reproducible and cost-effective manufacturing of high quality SiC bulk crystals. This article describes the state of the art in the crystal growth technology and quality improvement of SiC crystals for power device applications. The article also outlines the status of the SiC power device manufacturing and market and provides future prospect for the SiC semiconductor technology through reviewing the recent achievements in the technology.
In the last decade, studies on semiconducting diamond for the power device application have intensively been conducted in several research groups. A use of diamond crystals with low defect density is crucial for obtaining high blocking voltage. High quality and high purity of diamond crystals are also requested in the field of research on quantum information and quantum sensing using diamond. In this study, we proposed an advanced diamond growth method that removes crystalline defects effectively during the growth process of homoepitaxial diamond films. High purity diamond films were grown by utilizing a microwave plasma-assisted chemical vapor deposition system developed in NIMS and consisting of UHV-compatible vacuum components. By optimizing growth conditions with higher oxygen concentration of 2%, high-purity homoepitaxial (100) diamond layers, typical nitrogen concentration of which was less than 1 ppb, were successfully grown.
We have grown high purity n-type Mg2Si single crystals by the vertical Bridgman growth method using a pyrolitic graphite (PG) crucible and high purity Mg (5N or 6N-up) and Si (10N-grade) source metals. The saturated electron concentration and Hall mobility of the grown crystals were (1 - 2) × 1015 cm-3 and 480 - 485 cm2/Vs at room temperature. Mg2Si substrates prepared from the crystals had an enough crystalline quality to fabricate pn-junction photodiodes (PDs). The ring-electrode-type, pn-junction PD fabricated by the rapid thermal diffusion of Ag and conventional lift-off process showed a good photoresponse below 2 μm in wavelength. The detectivity D* of 1 × 1012 cmHz1/2/W has been achieved with the PDs under 1.31 μm laser diode (LD) bombardment at 77K.
It is reported that a crystal growth under high-oxygen-pressure atmosphere yields high-performance single crystals of ferrielectric AgNbO3. A single crystal grown via the Czochralski method at an oxygen pressure PO2 of 0.9 MPa exhibits a large polarization associated with a marked change in polarization hysteresis under an application of high electric field. Chemical analysis reveals that an increase in PO2 during crystal growth suppresses the deficiency of Ag and leads to a low leakage current. It is demonstrated that the AgNbO3 single crystal shows ferrielectric polarization associated with an electric-filed-induced phase transition to a ferroelectric phase under electric fields along the  axis.
Molten metallic halides reach the spherical shape driven by the surface tension when a residual moisture (H2O) is completely ridded from the raw material, the crucible, and atmosphere. We denote this condition as the “Liquinert” state meaning “liquid being in an inert state”, non-wetting and non-reactive with the crucible at high -temperature. The author has prepared high-quality metallic halides crystals by vertical Bridgman (VB) method when applying the “Liquinert” process. This technology enables us to obtain high quality inorganic crystals not only metallic halides but also metals and semi-conductors with contamination free from the crucible and atmosphere. In this review, the “Liquinert” process, its background, methodology, examples of applications in practical development of SrI2(Eu) and CaF2 are summarized.
A novel method for fabricating anisotropic collagen membranes, which regulate the preferred orientation, is developed. The generalized-high accuracy universal polarimeter (G-HAUP) method is used for simultaneous and quantitative evaluations of the optical anisotropy and optical activity. The evaluation of these optical quantities, enabled by the G-HAUP method, is beneficial to the field of tissue engineering.