• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.5-8
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• 2000

This paper proposes GaN film as a piezoelectric material for SAW(surface acoustic wave) filters. The fabricated GaN SAW filter exhibited a very high velocity of 5800 ㎧and relatively low insertion loss of -9.9 dB without matching circuit. From Smith's equivalent circuit model, the calculated electromechanical coupling factor (K$^2$) was about 4.$\pm$03％. which is larger than those obtained from other thin film piezoelectric materials and allows the realization of wider filter fractional bandwidths.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.388-395
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• 1998

This paper reports on a thermodynamic analysis for the GaN thick film growth by vapor phase epitaxy method. The thermodynamic calculation was performed using a chemical stoichiometric algorism. The simulation variables include the growth temperature in a range 400~1500 K, the gas ratios $(GaCl_3)/(GaCl_3+NH_3)$ and $(N_2)/(GaCl_3+NH_3)$. The theoretical calculation predicts that the growth temperature of GaN be in the lower range of 450~750 K than the experimental results. The difference in the growth temperature between the simulation and the experiments indicates that the vapor phase epitaxy of GaN is kinetically limited, presumably, due to the high activation energy of thin film growth.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1065-1066
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• 2000

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.13-14
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• 2008

$Al_2O_3$ thin films were deposited on GaN (0001) by remote plasma atomic layer deposition (RPALD) technique using trimethylaluminum (TMA) precursor and oxygen radicals in the temperature range of 25 ~ $500^{\circ}C$. Growth rate per cycle was varied with substrate temperature from 1.8 $\breve{A}$/ cycle at $25^{\circ}C$ to 0.8 $\breve{A}$/cycle at $500^{\circ}C$. The chemical structure of the $Al_2O_3$ thin films was studied using X-ray photo electron spectroscopy (XPS). Excellent electrical properties of $Al_2O_3$/GaN MIS capacitor were grown at $300^{\circ}C$ process temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.207-207
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• 2010

Both ZnO and GaN have excellent physical properties in optoelectronic devices such as blue light emitting diode (LED), blue laser diode (LD), and ultra-violet (UV) detector. The ZnO/GaN heterostructure, which has a potential to achieve the cost efficient LED technology, has been fabricated by using radio frequency (RF) sputtering, pyrolysis, metal organic chemical vapor deposition (MOCVD), direct current (DC) arc plasmatron, and pulsed laser deposition (PLD) methods. Among them, the PLD system has a benefit to control the composition ratio of the grown film from the mixture target. A 500-nm-thick ZnO film was grown by PLD technique on c-plane GaN/sapphire substrates. The post annealing process was executed at some varied temperature between from $300^{\circ}C$ to $900^{\circ}C$. The morphology and crystal structural properties obtained by using atomic force microscope (AFM) and x-ray diffraction (XRD) showed that the crystal quality of ZnO thin films can be improved as increasing the annealing temperature. We will discuss the post-treatment effect on film quality (uniformity and reliability) of ZnO/GaN heterostructures.

• Korean Journal of Crystallography
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• v.9 no.2
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• pp.131-137
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• 1998

결정결함의 밀도가 낮은 GaN epitaxy 막을 MOCVD(metal organic chemical vapour deposition) 방법에 의해 성장시켰다. 기판은 6H-SiC를 사용하였으며, AlN과 GaN으로 구성된 이중 buffer 층을 도입하였다. GaN buffer 층은 반응원료인 trimethyl gallium(TMG)과 NH3 가스를 교호식펄스공급(alternating pulsative supply, APS)방법에 의해 만들었다. AlN buffer/6H-SiC 위에 초기단계에 형성되는 GaN 섬은 APS처리에 의해 크기가 커지는 것을 AFM(atomic force microscope)으로 관찰하였다. Buffer 층의 역할은 그 위에 성막시킨 GaN epitaxy 막의 결정성과 결함밀도에 의해 조사하였다. 성막된 GaN의 결정구조와 결정성은 DCXRD(double crystal X-ray diffractormeter)에 의해 측정되었다. 결정결함은 EPD(etching pit density)를 측정하는 방법으로 알칼리혼합용에서 처리된 막을 SEM(scanning electron microscope)으로 관찰하였다.

• Journal of the Semiconductor & Display Technology
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• v.10 no.3
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• pp.29-33
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• 2011

Film growth rate and composition variation are numerically analyzed during the selective area growth of InGaN on the GaN triangular stripe microfacet in this study. Both the vapor phase diffusion and the surface diffusion are considered to determine the In composition on the InGaN surface. To obtain the In composition on the surface, flux of In atoms due to the surface diffusion is added to the concentration determined from the Laplace equation which is governing the gas phase diffusion. The solution model is validated by comparing the growth rates from the analyses to the experimental results of GaN and InN films. The In composition and resulting wave length are increased when the surface diffusion is considered. The In content is also increased according to the increasing mask width. The effect of mask width to the In content and wave length is increasing in the case of a small open region.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.377-382
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• 1998

GaN epilayers having good adhesion and quality were obtained directly on the sapphire {1120} substrates by the OMVPE method without introducing a buffer layer at the lower temperature. The preferred orientations of epilayers turned out to be <0002> and at least 4 kinds of epilayers were competitively grown. Slight distortions of lattices caused by lattice mismatches between sapphire and GaN were observed at the lattices within 2~3 nm region from the interface. Accordingly, TEM investigation revealed that GaN epilayers could be grown on sapphire {1120} planes without a buffer layer.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.54-57
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• 2002

We have grown undoped $In_ xGa_{1-x}N,\; In_xGa_{1-x}N:Si\;and\;In_{0.1}Ga_{0.9}N:Zn$ thin films by MOCVD at temperature between 880 and $710^{\circ}C which endows various In composition in the epilayer from 0.07 to 0.22 as examined using X-ray diffraction, optical absorption(OA), photocurrent (PC) and photoluminescence (PL). The In molar fraction estimated from PL results is higher than that from the OA, PC, and X-ray data for $X{\le}0.22$, which may be caused by phase separation. However, the In molar fraction estimated by X-ray diffraction, OA, PC and PL for $In_xGa_{1-x}N:Si$ does not show discrepancy. With the appropriate Zn doping in undoped $In_{0.1}Ga_{0.9}N$, the emission peak is shifted from 3.15 eV which originates from the band edge emission peak to 2.65 eV which resulted from the conduction band to acceptor transition due to a deep acceptor level.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.72-75
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• 1996

A hydride vapor phase epitaxy (HVPE) method is performed to prepare the GaN thin films on c-plane sapphire substrate. The full-width at half maximum of double crystal X-ray rocking curves from 20$\mu\textrm{m}$-thick GaN was 576 arcsecond. The photoluminescence spectrum measured 10 K shows the hallow bound exciton (I$_2$) line and weak donor-acceptor peak, however, there was not observed deep donor-acceptor pair recombination indicate the GaN crystals prepared in this study are of high purity and high crystalline quality. The GaN layer is n-type conducting with electron mobility of 72 $\textrm{cm}^2$/V$.$sec and with carrier concentration of 6 x 10$\^$18/cm/sup-3/.