• Applied Science and Convergence Technology
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• v.23 no.5
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• pp.296-300
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• 2014

The synthesis of pure and rare-earth doped gallium oxide (${\beta}-Ga_2O_3$) nanoparticles is reported. The synthesized nanoparticles are characterized with XRD, TEM, and PL analyses. Strong blue emission is observed from un-doped gallium oxide nanoparticles, while nanoparticles doped with $Eu^{3+}$ and $Tb^{3+}$ give strong red and green emissions, respectively. When doped with $Eu^{3+}$ and $Tb^{3+}$ together, gallium oxide nanoparticles emit white light. The CIE coordinate of the emitted light was found to be (0.33, 0.33), which is well within the white light region.

• Journal of the Korean Ceramic Society
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• v.51 no.3
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• pp.156-161
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• 2014

Gallium oxide ($Ga_2O_3$) powders were synthesized using a precipitation method and a polymerized complex method. TG-DSC, SEM, and XRD were performed to investigate the phase and morphology of the $Ga_2O_3$. In situ high-temperature XRD analysis revealed the crystal structure of $Ga_2O_3$ at different temperatures. The $Ga_2O_3$ obtained using the precipitation method and polymerized complex method were generally spherical-shaped particles and their average particle size was approximately 80 nm and $1{\mu}m$, respectively. The crystal structure of the $Ga_2O_3$ prepared by the precipitation method was changed from rhombohedral to monoclinic at $700^{\circ}C$, while monoclinic $Ga_2O_3$ was obtained directly from the precursor by the polymerized complex method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.1
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• pp.74-80
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• 2023

Gallium oxide (Ga₂O₃) thin films were grown on c-, a-, m-, r-plane sapphire substrates using a mist chemical vapor deposition system. Various growth temperature range of 400~600℃ was applied for Ga₂O₃ thin film deposition. Then, several structural properties were characterized such as film thickness, crystal phase, lattice orientation, surface roughness, and optical bandgap. Under the certain growth temperature of 500℃, all grown Ga₂O₃ featured rhombohedral crystal structures and well-aligned preferred orientation to sapphire substrate. The films grown on c-and r-plane sapphire substrates, showed low surface roughness and large optical bandgap compared to those on a-and m-plane substrates. Therefore, various sapphire orientation can be potentially applicable for future Ga₂O₃-based electronics applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.203-203
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• 2015

Gallium Oxide (Ga2O3) has been widely investigated for the optoelectronic applications due to its wide bandgap and the optical transparency. Recently, with the development of fabrication techniques in nanometer scale semiconductor materials, there have been an increasing number of extensive reports on the synthesis and characterization of Ga2O3 nano-structures such as nano-wires, nano-belts, and nano-dots. In contrast to typical vapor-liquid-solid growth mode with metal catalysts to synthesis 1-dimensional nano-wires, there are several difficulties in fabricating the nano-structures by using sputtering techniques. This is attributed to the fact that relatively low growth temperatures and higher growth rate compared with chemical vapor deposition method. In this study, Ga2O3 nanowires (NWs) were synthesized by using radio-frequency magnetron sputtering method. The NWs were then coated by Au thin films and annealed under Ar or N2 gas enviroment with no supply of Gallium and Oxygen source. Several samples were prepared with varying the post annealing parameters such as gas environment annealing time, annealing temperature. Samples were characterized by using XRD, SEM, and PL measurements. In this presentation, the details of fabrication process and physical properties of branched Ga2O3 NWs will be reported.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.2
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• pp.208-214
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• 2024

This reports the electrical properties of single-crystal β-gallium oxide (β-Ga₂O₃) vertical Schottky barrier diodes (SBDs) with a different guard ring structure. The vertical Schottky barrier diodes (V-SBDs) were fabricated with two types guard ring structures, one is with metal deposited on the Al₂O₃ passivation layer (film guard ring: FGR) and the other is with vias formed in the Al₂O₃ passivation layer to allow the metal to contact the Ga₂O₃ surface (metal guard ring: MGR). The forward current values of FGR and MGR V-SBD are 955 mA and 666 mA at 9 V, respectively, and the specific on-resistance (R_on,sp) is 5.9 mΩ·cm² and 29 mΩ·cm². The series resistance (R_s) in the nonlinear section extracted using Cheung's formula was 6 Ω, 4.8 Ω for FGR V-SBD, 10.7 Ω, 6.7 Ω for MGR V-SBD, respectively, and the breakdown voltage was 528 V for FGR V-SBD and 358 V for MGR V-SBD. Degradation of electrical characteristics of the MGR V-SBD can be attributed to the increased reverse leakage current caused by the guard ring structure, and it is expected that the electrical performance can be improved by preventing premature leakage current when an appropriate reverse voltage is applied to the guard ring area. On the other hand, FGR V-SBD shows overall better electrical properties than MGR V-SBD because Al₂O₃ was widely deposited on the Ga₂O₃ surface, which prevent leakage current on the Ga₂O₃ surface.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.5
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• pp.504-508
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• 2022

Single crystal gallium oxide (Ga₂O₃) has been an emerging material for power semiconductor applications. However, the defect distribution of Ga₂O₃ substrates needs to be carefully characterized to improve crystal quality during crystal growth. We analyzed the type and the distribution of defects on commercial (-201) Ga₂O₃ substrates to get a basic standard prior to growing Ga₂O₃ crystals. Etch pit technique was employed to expose the type of defects on the Ga₂O₃ substrates. Synchrotron white beam X-ray topography was also utilized to observe the defect distribution by a nondestructive manner. We expect that the observation of defect distribution with three-dimensional geometry will also be useful for other crystal planes of Ga₂O₃ single crystals.

• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.134-138
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• 1997

$Dy^{3+}-(or Tm^{3+}-)$ doped $Ga_2O_3 \;and\; ZnGa_2O_4$ phosphors were prepared using the solid state reaction method to investigate their photoluminescent characteristics. Under 254 nm excitation, $Dy^{3+}-doped Ga2_O_3$ exhibited two emission bands of 460~505nm and 570~600nm. On the other hand, $Dy^{3+}-(or Tm^{3+}-)$ doped $ZnGa_2O_4 $phosphors exhibited a broad-band emission extending from 330 nm to 610 nm, peaking at about 430 nm(or 370 nm). In this study, an emission peak shift of nealy 50 nm towards longer wavelength region was observed with $Dy^{3+}$ doping in the $ZnGa_2O_4 $.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.138-143
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• 2022

We analyzed the influence of post-annealing on Ga₂O₃/n-type 4H-SiC heterojunction diode. Gallium oxide (Ga₂O₃) thin films were deposited by radio frequency (RF) sputtering. Post-deposition annealing at 950℃ in an Oxygen atmosphere was performed. The material properties of Ga₂O₃ and the electrical properties of the diodes were investigated. Atomic Force Microscopy (AFM), X-Ray Diffraction and Scanning Electron Microscope (SEM) images show a significant increase in the roughness and crystallinity of the O₂-annealed films. After Oxygen annealing X-ray Photoelectron Spectroscopy (XPS) shows that the atomic ratio of oxygen increases which is related to a decrease in oxygen vacancy within the Ga₂O₃ film. The O₂-annealed diodes exhibited higher on-current and lower leakage current. Moreover, the ideality factor, barrier height, and thermal activation energy were derived from the current-voltage curve by increasing the temperature from 298 - 434K.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.236.1-236.1
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• 2014

Compounds of Ga, such as gallium oxide (Ga2O3) and gallium nitride (GaN), are of interest due to its unique properties in semiconductor application. In particular, GaN has the potentially application for optoelectronic device such as light-emitting diodes (LEDs) and laser diodes (LDs) [1]. Nanoparticle is an interesting material due to its unique properties compared to the bulk equivalents. In this report, we develop a synthesizing method for gallium nitride nanoparticle using non-thermal plasma. For gallium source, the gallium is heated by thermal conduction of tungsten boat which is heated by eddy current induced from RF current in antenna. Nitrogen source for nanoparticle synthesis are from inductively coupled plasma with N2 gas. The synthesized nano particles are analyzed using field-emission scanning microscope (FESEM), transmission electron microscope (TEM) and x-ray photoelectron spectroscopy (XPS). The synthesized particles are investigated and discussed in wide range of experiment conditions such as flow rate, pressure and RF power.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.6
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• pp.302-308
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• 2013

In this study, we report the synthesis and characteristics of gallium oxide ($Ga_2O_3$) nanoparticles prepared by the polymerized complex method. $Ga_2O_3$ nanoparticles were synthesized using $Ga(NO_3)_3$, ethylene glycol, and citric acid as the starting materials at a low temperature of $500{\sim}800^{\circ}C$. The temperature of the weight reduction by the loss of organic precursor was revealed using TG-DTA analysis. The crystal structural change of $Ga_2O_3$ nanoparticles by the annealing process was investigated by XRD analysis. The morphologies and the size distributions of $Ga_2O_3$ nanoparticles were analyzed using SEM.