• 한국결정성장학회지
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• 제9권2호
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• pp.168-172
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• 1999

HVPE 법으로 sapphire 기판 위에 두께 9$\mu\textrm{m}$의 GaN film을 성장하였다. Sapphire위에 직접 성장된 GaN film은 crack free로 mirror surface를 나타내었고 dislocation density는 $2{\times}10^9/cm^2$이었다.$SiO_2$ mask pattern을 사용하여 성장된 ELO GaN film도 대부분이 mirror surface를 나타내었으나 표면 일부에서 coalescence가 덜 이루어져 stripe 방향으로 hole이 존재하였다. ELO GaN film의 mask 윗부분은 window 부분에 비해 낮은 dislocation density를 나타냈다. 특히 mask center와 window사이 영역에서는 거의 dislocation이 없었다. ELO GaN film의 dislocation density는 평균 $8{\times}10^7/cm^2$.이었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.41-45
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• 2003

Impurities transmuted in GaN thin film and GaN nanowires after neutron irradiation are studied in this work. The structural properties of GaN nanowires were shown using by Transmission Electron Microscope(TEM). Transmuted impurities that are expected to be doped into GaN thin film and GaN nanowires are then confirmed by photoluminescence(PL). Transmuted atom in GaN materials is Ge atom, Ge-related peaks in GaN thin film lead to emit at 2.9eV, 2.25eV. But emission bands at 2.9eV, 2.25eV are not shown in PL spectra of GaN nanowires. Our experimental results are expected to give deep impact on nano-material doping technology for the achievement of the fabrication of nano-devices.

• 한국전기전자재료학회논문지
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• 제17권5호
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• pp.497-501
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• 2004

The crystal structure of the GaN film on the AIN buffer layer grown by R. F sputtering with different thickness has been studied using X-ray scattering and transmission electron microscopy(TEM). The interface roughness between the AIN buffer layer and the epitaxial GaN film, due to crossover from planar to island grains, produced edge dislocations. The strain, coming from lattice mismatch between the AIN buffer layer and the epitaxial GaN film, produced screw dislocations. The density of the edge and screw dislocation propagating from the interface between the GaN film and the AIN buffer layer affected the electric resistance of GaN film.

• 한국결정성장학회지
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• 제14권1호
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• pp.33-36
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• 2004

고밀도 GaN 타겟의 레이저 어블레이션으로 상온에서 비정질 GaN 박막을 제조하였다. 다양한 Ar 압력 및 레이저 에너지로 증착된 박막의 표면미세구조 및 조성분석 결과, 10Pa의 압력하에 증착된 박막은 smooth한 표면을 갖는 비정질 GaN로 구성되었음을 확인하였으며, 특히 200mJ/pu1se로 증착된 박막은 저 에너지에서 증착된 박막과 비교하여 결정성의 증가 및 화학양론에 가까운 조성을 나타냈다. 상온 photoluminescence spectra로부터 비정질 GaN 박막은 약 2.8eV에서 강한 band gap발광특성이 관측되었으며, 200mJ/pu1se의 10 Pa에서 가장 높은 발광효율을 나타냈다.

• 한국재료학회지
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• 제24권12호
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• pp.645-651
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• 2014

GaN is most commonly used to make LED elements. But, due to differences of the thermal expansion coefficient and lattice mismatch with sapphire, dislocations have occurred at about $109{\sim}1010/cm^2$. Generally, a low temperature GaN buffer layer is used between the GaN layer and the sapphire substrate in order to reduce the dislocation density and improve the characteristics of the thin film, and thus to increase the efficiency of the LED. Further, patterned sapphire substrate (PSS) are applied to improve the light extraction efficiency. In this experiment, using an AlN buffer layer on PSS in place of the GaN buffer layer that is used mainly to improve the properties of the GaN film, light extraction efficiency and overall properties of the thin film are improved at the same time. The AlN buffer layer was deposited by using a sputter and the AlN buffer layer thickness was determined to be 25 nm through XRD analysis after growing the GaN film at $1070^{\circ}C$ on the AlN buffer CPSS (C-plane Patterned Sapphire Substrate, AlN buffer 25 nm, 100 nm, 200 nm, 300 nm). The GaN film layer formed by applying a 2 step epitaxial lateral overgrowth (ELOG) process, and by changing temperatures ($1020{\sim}1070^{\circ}C$) and pressures (85~300 Torr). To confirm the surface morphology, we used SEM, AFM, and optical microscopy. To analyze the properties (dislocation density and crystallinity) of a thin film, we used HR-XRD and Cathodoluminescence.

• Bulletin of the Korean Chemical Society
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• 제24권7호
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• pp.953-956
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• 2003

Hexagonal GaN (h-GaN) films have been grown on Si(111) substrates by metal organic chemical vapor deposition using the azidodiethylgallium methylamine adduct, Et₂Ga(N₃)·NH₂Me, as a new single precursor. Deposition was carried out in the substrate temperature range 385-650 °C. The GaN films obtained were stoichiometric and did not contain any appreciable amounts of carbon impurities. It was also found that the GaN films deposited on Si(111) had the [0001] preferred orientation. The photoluminescence spectrum of a GaN film showed a band edge emission peak characteristic of h-GaN at 378 nm.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.132-132
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• 2011

The sheet resistance (Rs) of undoped GaN films on AlN/c-plane sapphire substrate was investigated in which the AlN films were grown by R. F. magetron sputtering method. The Rs was strongly dependent on the AlN layer thickness and semi-insulating behavior was observed. To clarify the effect of crystalline property on Rs, the crystal structure of the GaN films has been studied using x-ray scattering and transmission electron microscopy. A compressive strain was introduced by the presence of AlN nucleation layer (NL) and was gradually relaxed as increasing AlN NL thickness. This relaxation produced more threading dislocations (TD) of edge-type. Moreover, the surface morphology of the GaN film was changed at thicker AlN layer condition, which was originated by the crossover from planar to island grains of AlN. Thus, rough surface might produce more dislocations. The edge and mixed dislocations propagating from the interface between the GaN film and the AlN buffer layer affected the electric resistance of GaN film.

• 한국전기전자재료학회논문지
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• 제30권7호
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• pp.427-431
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• 2017

In this paper, we discuss ${\beta}-Ga_2O_3$ thin films that have been grown on freestanding GaN (FS-GaN) using furnace oxidation. A GaN template was grown by horizontalhydride vapor phase epitaxy (HVPE), and FS-GaN was fabricated using the laser lift off (LLO) system. To obtain ${\beta}-Ga_2O_3$ thin film, FS-GaN was oxidized at $900{\sim}1,100^{\circ}C$. Surface and cross-section of prepared ${\beta}-Ga_2O_3$ thin films were observed by field emission scanning electron microscopy (FE-SEM). The single crystal FS-GaNs were changed to poly-crystal ${\beta}-Ga_2O_3$. The oxidized ${\beta}-Ga_2O_3$ thin film at $1,100^{\circ}C$ was peel off from FS-GaN. Next, oxidation of FS-GaNwas investigated for 0.5~12 hours with variation of the oxidation time. The thicknesses of ${\beta}-Ga_2O_3$ thin films were measured from 100 nm to 1,200 nm. Moreover, the 2-theta XRD result indicated that (-201), (-402), and (-603) peaks were confirmed. The intensity of peaks was increased with increased oxidation time. The ${\beta}-Ga_2O_3$ thin film was generated to oxidize FS-GaN.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.121-121
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• 1999

Gallium nitride (GaN) semiconductor is intensively under investigation for commercialization of short wavelength light emitting devices and laser diodes. One of serious obstacles to overcome is to reduce the defect density in GaN film grown by various techniques such as MOCVD, HVPE, etc. Many research groups including SAIT are trying to improve the defect density to 106-107/cm2 from the level of 108-1010/cm2. We have investigated epitaxial growth behaviour of GaN thin and thick films under hidride vapour phase epitaxy (HVPE) condition. In this report, we present the microstructural and crystallographical characteristics of the GaN films grown on sapphire (0001) substrate which were studied by both conventional and high-resolution transmission electron microscopy (TEM). Also we present some microscopic analysis results obtained from GaN films grown by ELO(dpitzsial lateral overgrowth)-HVPE and from GaN quantum well structures grown by MOCVD. Another serious problem in growing GaN thick film by HVPE is internal micro-cracks. We also comment the origin of the micro-crack.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.574-577
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• 2001

GaN thin films on sapphire were grown by rf magnetron sputtering with ZnO buffer layer. The dependence of GaN film quality on ZnO buffer layer was investigated by X-ray diffraction(XRD). The improved film quality has been obtained by using thin ZnO buffer layer. Using Auger electron spectroscopy(AES), it was observed that the annealing process improved the GaN film quality. The surface roughness according to the annealing temperatures(700, 900, 1100$^{\circ}C$) were investigated by AFM(atomic force microscopy) and it was confirmed that the crystallization was improved by increasing the annealing temperature. Photoluminescence at 8K shows a near-band-edge peak at 3.2eV with no deep level emission.