• Journal of IKEEE
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• v.22 no.2
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• pp.427-431
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• 2018

This research was worked about $Ga_2O_3$ Epi wafer that was one of the mose wide band gap semiconductors to be used power semiconductor industry. This wafer was grown $5.3{\mu}m$ thickness on Sn doped $Ga_2O_3$ Substrate by HVPE(Hydride Vapor Phase Epitaxy). Generally, we can fabricate 600V class power semiconductor devices when the thickness of compoound power semiconductor is $5{\mu}m$. but in case of $Ga_2O_3$ Epi wafer, we can obtain over 1000V class. As a result of J-V measurment of the grown $Ga_2O_3$ Epi wafer, we obtain $2.9-7.7m{\Omega}{\cdot}cm^2$ on resistance. Specially, in case of reverse, we comfirmed a little leakage current when the reverse voltage is over 200V.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.9
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• pp.666-672
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• 2003

In this paper, we described the fabrication and the performance of wavelength tunable distributed bragg reflector (DBR) laser diode (LD), having different waveguide coupling mechanisms; integrated-twin-guide (ITG) DBR-LD and butt coupled (BT) DBR-LD. This deviceis fabricated by metal organic vapor phase epitaxy (MOVPE) growth and planar buried heterostructure (PBH)-type transverse current confinement structure. The result of measurement, the optical performance of BT-DBR-LD is better over 2 times than that of ITG-DBR-LD at the variation of threshold current and output power, and slop efficiency due to the higher coupling efficiency of the butt coupled structure than the integrated twin guide structure. The maximum wavelength tuning range is about 7.2nm for ITG DBR-LD and 7.4nm for BT DBR-LD. Both types of lasers have a very high yield of single mode operation with a side-mode suppression ratio of more than 35dB.

• Applied Microscopy
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• v.25 no.3
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• pp.82-89
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• 1995

High resolution transmission electron microscopic observations on quaternary $Zn_{1-x}Mg_{x}S_y$ $S_{1-y}$(x=0.13, y=0.16) on (001) GaAs substrate grown up to $1.2{\mu}m$ with 20nm ZnSe buffer layer at $300^{\circ}C$ by RIBER MBE system which has a single growth chamber were investigated by HRTEM working at 300kV with point resolution of 0.18nm. The ZnSe buffer layer maintains the coherency with the GaAs substrate. The stacking faults had begun at ZnSe buffer/$Zn_{1-x}Mg_{x}S_{y}S_{1-y}$ interface, whose length and spacing became larger than 60nm and wider than 40nm, respectively. The inverse triangular stacking fault was bounded by stacking faults which were formed on {111} planes with different variants. There exists rare stacking faults inside the triangular defect. The epilayer surrounded by the straight stacking faults, which had formed in the same direction, became the columnar structure.

• Applied Microscopy
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• v.25 no.3
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• pp.75-81
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• 1995

The microstructural characterization of ternary $ZnS_{x}Se_{1-x}$(x=0.085) on GaAs(001) substrate grown up to $2{\mu}m\;at\;300^{\circ}C$ by molecular beam epitaxy(MBE) which has a single growth chamber was investigated by high resolution transmission electron microscope (HRTEM) working at 300 kV with point resolution of 0.18nm. The interface in the ZnSSe/GaAs specimen maintains a pseudomorphism with the substrate, but the epilayer has high density of stacking faults and moire fringes. The pits which had formed along <111> direction were found at the interface of ZnSSe/GaAs. The pits were responsible for producing defects in both epilayer and substrate. The wavy interface which has the difference of 15nm in height was found to maintain the pseudomorphism with the substrate and no stacking faults were found around the interface. However there exists faint and fine moire fringes in the epilayer near interface.

• Journal of the Korean Vacuum Society
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• v.7 no.4
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• pp.341-347
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• 1998

We analyzed photoreflectance (PR) characterization of the $Al_xGa_{1-x}As$ epilayer grown by molecular beam epitaxy (MBE) method. The band-gap energy $(E_0)$ satisfying low power Franx-Keldysh (LPFK) due to GaAs buffer layer is 1.415 eV, interface electricall field $(E_i)$ is 1.05$\times$$10^4$V/cm, carrier concentration (N) is $1.3{\times}10^{15}\textrm{cm}^{-3}$. In PR spectrum intensity analysis at 300 K the $A^*$ peak below $(E_0)$ signal is low and distorted because of residual impurity in sample growth. The trap characteristic time ${\tau}_i$ of GaAs buffer layer is about 0.086 ms, and two superposed PR signal near 1.42eV consist of the third derivative signal of chemically eteched GaAs substrate and Franz-Keldysh oscillation (FKO) signal due to GaAs buffer layer.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.354-361
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• 1999

The films annealed after physical deposition of titanium and chemical deposition of amorphous silicon by plasma were formed Si-rich titanium silicide with a good quality of crystallinity and had the various lattice structures due to orientation of lattices for epitaxy growth during annealing process. Band gap of the titanium silicide had 1.14~1.165 eV and the films annealed after chemical deposition of a-Si:H by plasma were influenced by a-Si and the dangling bond offered by desorption of hydrogen. Urbach tail ($E_0$) of the films annealed after physical deposition of Ti was nearly constant within a range of 0.045~0.05 eV, and the number of defect in films annealed after chemical deposition of a-Si:H by plasma was about 2~3 times more than that in annealed Ti/Si films.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.732-736
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• 2013

AlN epilayers were grown on a c-plane sapphire substrate using hydride vapor phase epitaxy (HVPE). A series of AlN epilayers were grown at $1120^{\circ}C$ with V/III ratios 1.5, 2.5 and 3.5, and the influence of V/III ratio on their properties was investigated. As the V/III ratio was increased, the surface roughness (RMS roughness), Raman shift of $E_2$ high peaks and full-width at half-maximum (FWHM) of symmetrical (002) & asymmetrical (102) of the AlN epilayers increased. However, the intensities of the Raman $E_2$ high peaks were reduced. This indicates that the crystal quality of the grown AlN epilayers was degraded by activation of the parasitic reaction as the V/III ratio was increased. Smooth surface, stress free and high crystal quality AlN epilayers were obtained at the V/III ratio of 1.5. The crystal quality of AlNepilayers is worsened by the promotion of three-dimensional (3D) growth mode when the flow of $NH_3$ is high.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.222-222
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• 2011

Titanium dioxide (TiO2) has a number of applications in optics and electronics due to its superior properties, such as physical and chemical stability, high refractive index, good transmission in vis and NIR regions, and high dielectric constant. Atomic layer deposition (ALD), also called atomic layer epitaxy, can be regarded as a special modification of the chemical vapor deposition method. ALD is a pulsed method in which the reactant vapors are alternately supplied onto the substrate. During each pulse, the precursors chemisorb or react with the surface groups. When the process conditions are suitably chosen, the film growth proceeds by alternate saturative surface reactions and is thus self-limiting. This makes it possible to cover even complex shaped objects with a uniform film. It is also possible to control the film thickness accurately simply by controlling the number of pulsing cycles repeated. We have investigated the ALD of TiO2 at 100$^{\circ}C$ using precursors titanium tetra-isopropoxide (TTIP) and H2O on -O, -OH terminated Si surface by in situ X-ray photoemission spectroscopy. ALD reactions with TTIP were performed on the H2O-dosed Si substrate at 100$^{\circ}C$, where one cycle was completed. The number of ALD cycles was increased by repeated deposition of H2O and TTIP at 100$^{\circ}C$. After precursor exposure, the samples were transferred under vacuum from the reaction chamber to the UHV chamber at room temperature for in situ XPS analysis. The XPS instrument included a hemispherical analyzer (ALPHA 110) and a monochromatic X-ray source generated by exciting Al K${\alpha}$ radiation (h${\nu}$=1486.6 eV).

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.152-152
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• 2011

Silicon 기반의 환경에서 연구 및 제조되는 전자소자는 반도체의 기술이 발전함에 따라 chip 선폭의 크기가 30 nm에서 20 nm, 그리고 그 이하의 크기로 점점 더 작아지는 요구에 직면하고 있다. 탄소나노 구조와 나노와이어 기술이 Silicon을 대신할 다음세대 기술로 주목받고 있다. 많은 연구결과들 중에서 III-V CMOS가 가장 빠른 접근 방법이라 예상한다. III-V족 물질을 이용하면 electron 보다 수십 배 이상의 이동도를 얻을 수 있으나 p-type의 구조를 구현하는 것이 해결해야 할 문제이다. p-type 3-5 족 화합물을 이용하여 에너지 밴드 갭의 변화를 가능하게 한다면 hole의 이동도를 크게 향상시킬 수 있어 silicon 기반의 p-type 소자보다 2~3배 더 빠른 소자의 구현이 가능하다. 3-5족 화합물 반도체의 성장 기술이 많이 진보되어 이를 이용하여 고속 소자를 구현한다면 시기적으로 더욱 빨리 다가올 것이라 예측한다. 에너지 밴드갭의 변화와 격자 부정합을 고려하여 SI InP 기판에 GaSb 물질을 채널로 사용한 p-type 2-dimensional hole gas (2DHG) 소자를 구현하였다. 관찰된 소자 구조의 박막 상태의 특징을 보이며 10 um ${\times}$ 10 um AFM 측정결과 1 nm 이하의 표면 거칠기를 가지며 상온에서의 hole 이동도는 약 650 cm2/Vs이고 sheet carrier density는 $5{\times}1012$ /cm2의 결과를 확인하였다. 실험결과 InP 기판위에 채널로 사용된 GaSb 박막을 올리는데 있어 가장 중요한 것은 Phosphorus, Arsenic, 그리고 Antimony 물질의 양과 이들의 변화시간의 조절이다. 본 발표에서 Semi-insulating InP 기판위에 electron이 아닌 hole을 반송자로 이용한 차세대 고속 전자소자를 구현하고자 하여 MBE (Molecular Beam Epitaxy)로 p-type 소자를 구현하여 실험하였다. 아울러 더욱 빠른 소자의 구현을 위하여 세계의 유수 그룹들의 연구 결과들과 앞으로 예상되는 고속 소자에 대해서 비교와 함께 많은 기술에 대해 논의하고자 한다.

• Journal of the Korean Chemical Society
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• v.39 no.1
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• pp.1-6
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• 1995

The surface of a sapphire substrate used for hetero-epitaxy was chemically polished in a mixture of $H_3PO_4\;and\;H_2SO_4$ solution. The extent of etching for various crystal orientations was found to be dependent on the etching time at $315{\pm}2^{\circ}C$ and at the composition of $H_2SO_4 : H_3PO_4$=3 : 1. In addition, the etching rates of the substrates were investigated in the mixture of $H_2SO_4 : H_3PO_4$=3 : 1 by volume and in the temperature range of 280~320$^{\circ}C$. From the plot of log R against 1/T, the activation penergy ($(E_a)$) was found to be in the order of $({\bar1}012) > (10{\bar1}0) > (11{\bar2}0) > (0001)$ plane. After removing the surface layers of the sapphire with (0001), $({\bar1}012),\;(10{\bar1}0)\;and\;(11{\bar2}0)$ plane by a thickness of 64.6, 46.5, 16.2 and 5.1 ${\mu}m$, respectively, the morphology of the resulting surface was observed by SEM.