Shizυo Fujita

Wide-bandgap semiconductors are expected to be applied to solid-state lighting and power devices, supporting a future energy-saving society. While GaN-based white LEDs have rapidly become widespread in the lighting industry, SiC- and GaN-based power devices have not yet achieved their popular use, like GaN-based white LEDs for lighting, despite having reached the practical phase. What are the issues to be addressed for such power devices? In addition, other wide-bandgap semiconductors such as di

Abstract The recent progress and development of corundum-structured III-oxide semiconductors are reviewed. They allow bandgap engineering from 3.7 to ∼9 eV and function engineering, leading to highly durable electronic devices and deep ultraviolet optical devices as well as multifunctional devices. Mist chemical vapor deposition can be a simple and safe growth technology and is advantageous for reducing energy and cost for the growth. This is favorable for the wide commercial use of devices at l

Origin of memory traps in chemically vapor‐deposited silicon nitride films was investigated. Electron‐spin resonance and infrared absorption measurements revealed the existence of silicon dangling bonds which have three‐folded configuration. Correlation between the spin density and the metal‐nitride‐oxide‐semiconductor (MNOS) memory characteristics was studied, and it was suggested that silicon dangling bonds are responsible for the trap states which cause not only hopping conduction, but also m

Abstract Homoepitaxial single-crystal beta gallium oxide (β-Ga 2 O 3 ) films were fabricated by the mist chemical vapor deposition method. The crystallinity of the films grown markedly depended on growth temperature, and the optimum growth temperatures were found to be 700–800 °C. Using unintentionally doped β-Ga 2 O 3 films grown on Sn-doped β-Ga 2 O 3 (010) substrates, the fabrication of Schottky barrier diodes was demonstrated. Furthermore, we fabricated electrically conductive Sn-doped β-Ga

Abstract Efforts have been made to reduce the density of defects in corundum-structured α-Ga 2 O 3 thin films on sapphire substrates by applying quasi-graded α-(Al x Ga 1− x ) 2 O 3 buffer layers. Transmission electron microscopy images revealed that most strains were located in the α-(Al x Ga 1− x ) 2 O 3 buffer layers, and that the total density of dislocations in the α-Ga 2 O 3 thin films was successfully decreased by more than one order of magnitude compared with that without buffer layers,