2022, Vol.32, No.2

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

Ga2O3 thin films were grown on n-type Si substrates at various growth temperatures of 500, 550, 600, 650 and 700°C. The Ga2O3 thin films grown at 500°C and 550°C were characterized as featureless flat surface. Grown at highertemperatures (600, 650, and 700°C) showed very rough surface morphology. To figure out the annealing effect on the thin films grown at relatively low temperatures (500, 550, 600, 650 and 700°C), the Ga2O3 films were thermally treated at 900°C for 10 minutes. Crystal structure of the Ga2O3 f ilms g rown a t 500 and 550°C were changed from amorphous to polycrystallinestructure with flat surface. Ga2O3 film grown at 550°C was chosen for the fabrication of a Schottky barrier diode (SBD). Electrical properties of the SBDs depend on the thermal treatment were evaluated. A MSM type photodetector wasmade on the low temperature grown Ga2O3 thin film. The photocurrent for the illumination of 266 nm wavelength showed 5.32 times higher than dark current at the operating voltage of 10 V.

The physical properties of the noble metal current-collector used for fuel cells are greatly influenced by the material porosity. Therefore, increasing the porosity of the material studies has attracted much attention. One of the most representative strategies is to use porosity additives in sintering materials. The conventional porosity additive had a threedimensional structure of a spherical powder. In this study, porosity additive with 2-dimensional (2D) nanosheet was used todecrease the sintering density of Ag current-collector and its effect was confirmed. As a 2D layered structure material, 1 nm-thick RuO2 nanosheets were used as porosity additives.

In this study, a heat treatment experiment was conducted to select a new melt composition that can easily control the unintentionally doped nitrogen (N-UID) without degrading the SiC single crystal quality during TSSG process. The experiment was carried out for about 2 hours at a temperature of 1900°C under Ar atmosphere. The used melt composition is based on either Si-Ti 10 at% or Si-Cr 30 at%, and also Co or Sc transition metals, which are effective for carbon solubility, were added at 3 at%, respectively. After the experiment, the crucible was cross-sectionally cut, and evaluated the Si-C reaction layer on the crucible-melt interface. As a result, with Sc addition, Si-C reaction layers uniformly occurred with a Si-infiltrated layer (~550 µm) and a SiC interlayer (~23 µm). This result represented that the addition of Sc is an effective transition metal with high carbon solubility and can feed carbon sources into the melt homogeneously. In addition, Sc is well known to have low reactivity energy with nitrogen compared to other transition metals. Therefore, we expect that both growth rate and Nitrogen UID can be controlled by Si-Sc based melt in the TSSG process.