2022, Vol.32, No.4

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

β-Gallium oxide (Ga₂O₃), an ultra-wide bandgap semiconductor, has attracted great attention due to its promising applications for high voltage power devices. The most stable phase among five different polytypes, β-Ga₂O₃ has the wider bandgap of 4.9 eV and higher breakdown electric field of 8 MV/cm. Furthermore, it can be grown from melt source, implying higher growth rate and lower fabrication cost than other wide bandgap semiconductors such as SiC, GaN and diamond for the power device applications. In this study, β-Ga₂O₃bulk crystals were grown by the edge-defined film-fed growth (EFG) process. The growth direction and the principal surface were set to be the [010] direction and the (100) plane of the β- Ga₂O₃ crystal, respectively. The spectra measured by Raman analysis could exhibit the crystal phase and impurity doping in the β-Ga₂O₃ ingot, and the crystallinity quality and crystal direction were analyzed using high-resolution X-ray diffraction (HRXRD). The crystal quality and various properties of as-grown β-Ga₂O₃ ribbon was systematically analyzed in order to investigate the spatial variation in entire crystal grown by EFG method.

The inside of a quartz glass crucible for semiconductor processing, called a transparent layer, is manufactured using synthetic silica powder. Bubbles existing in the transparent layer of the crucible cause a problem of reducing the quality of the crucible as well as the yield of the silicon ingot. Therefore, the main goal of the synthetic silica powder, which is the raw material of the transparent layer, is to minimize the bubble generation factor. For this purpose, in the case of synthetic silica powder, it is necessary to minimize silanol groups, carbon and pores. In this study, synthetic silica gel was prepared using the sol-gel method, and changes in carbon content and specific surface area were investigated according to calcination temperature and dwelled time in a two-stage calcination process. The first-stage calcination process was performed between 500°C and 600°C and the second-stage calcination process was performed between 1000°C and 1100°C. The dwelled time was carried out from 10 minutes to a maximum of 12 hours. The carbon content of the powder calcined at 1000°C for 1 hour was 0.0031 wt.%, and the specific surface area of the powder calcined at 1100°C for 12 hours was 16.6 m²/g.

The crystal structure, grain growth behavior, and dielectric properties of BaTiO3 have been studied with the addition of Dy2O3. The powders were synthesized at ratios of (100-x)BaTiO3-xDy2O3 (mol%, x = 0, 0.5, 1.0, 2.0) by a conventional solid-state synthesis, and the powder compacts were sintered at 1250°C for 2 hours in air. As the amount of added Dy2O3 was increased, the crystal structure of the sintered samples changed from a tetragonal to a pseudo-cubic structure, and the tetragonality decreased. In addition, a secondary phase of Ba12Dy4.67Ti8O35 appeared when Dy2O3 was added. The average grain size after sintering decreased and abnormal grains appeared as the amount of Dy2O3 increased. It can be explained that the grain growth behavior of the Dy2O3 added-BaTiO3 occurs due to the two-dimensional nucleation and growth, and is governed by the interface reaction. Further, the correlation between crystal structure, microstructure, and dielectric properties was discussed.