• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.8
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• pp.81-87
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• 1993

The growth thickness uniformity of epitaxial layers deposited using a moiecular beam epitaxy system is calculated from the arrangement of molecular beam source and the substrate and the geometric dimensions of the crucible in order to predict the optimum design conditions of the prototype MBE system. The thickness uniformity better than 5% over a 3-inch wafer can be obtained by keeping the distance between the substrate and the crucible's orifice longer than 20cm, the tapering angle of the crucible larger than 6$^{\circ}$, and the angle between the normal to the substrate at the center and the crucible axis as larger as possible. In addition, the growth yield decreases to below 51% as the distance between the substrate and the orifice becomes longer than 25cm.

• Journal of Magnetics
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• v.11 no.4
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• pp.170-181
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• 2006

Spin dependent tunneling has enormously activated the field of magnetism in general, and in particular spin transport studies, in the past ten years. Thousands of articles related to the subject have appeared with many fundamental results. Importantly, there is great interest in their potential for application. There was another surge of activity in this field since the past five years - created by the theoretical prediction of a large tunnel magnetoresistance that arises due to band symmetry matched coherent tunneling in epitaxial magnetic tunnel junctions with (001) MgO barrier and experimentally well demonstrated. This further development in the field has boosted the excitement in both fundamental science as well as the possibility of application in such as magnetic random access memory, ultra sensitive read heads, biosensors and spin torque diodes. This review is a brief coverage of the field highlighting the literature that deals with magnetic tunnel junctions having epitaxial MgO tunnel barriers.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.2
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• pp.169-174
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• 2014

As a versatile processing method for nanoscale memory integration, laser-induced epitaxial growth is proposed for the fabrication of vertical Si channel (VSC) transistor. The fabricated VSC transistor with 80 nm gate length and 130 nm pillar diameter exhibited field effect mobility of $300cm^2/Vs$, which guarantees "device quality". In addition, we have shown that this VSC transistor provides memory operations with a memory window of 700 mV, and moreover, the memory window further increases by employing charge trap dielectrics in our VSC transistor. Our proposed processing method and device structure would provide a promising route for the further scaling of state-of-the-art memory technology.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.156-157
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• 2005

Monte Carlo photon simulation 기법을 사용하여 광추출효율 관점에서 InGaN LED를 분석하였다. InGaN/sapphire 칩의 경우, AlInGaP나 InGaN/SiC 칩에서와는 달리, 칩의 측벽면을 기울여 주는데서 오는 광추출효율 개선 효과는 매우 미미하였다. 이는 InGaN/sapphire 칩의 경우 사파이어 기판의 굴절률 상대적으로 작아서 활성층으로부터 생성된 광자들의 상당량이 기판으로 넘어갈 때 전반사현상으로 말미암아 기판으로 넘어가지 못하고 상대적으로 두께가 매우 얇은 에피택시 층에 갇히기 때문으로 파악되었다. 이와 같은 효과는 epitaxial side down mount의 광추출효율이 크게 개선되지 못하는 원인으로도 작용하게 되는데, epitaxial side down mount의 잠재력을 살릴 수 있는 방안의 하나는 texture된 기판위에 결정층을 성장시키는 것이라고 할 수 있다.

• Journal of the Korean Ceramic Society
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• v.30 no.7
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• pp.578-588
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• 1993

Highly c-axis oriented ferroelectric PbTiO3 thin films were deposited on MgO single crystal substrates by RF magnetron sputtering. We have studied the effects of substrate temperature, RF input power, gas comosition, gas pressure and deposition rate on the chemical and structural characteristics of PbTiO3 thin films. The epitaxy relationship of c-axis oriented films was found to be PbTiO3{100}//MgO(100) and their microstructures were highly mosaic. It was found that the most important parameter to achieve epitaxial PbTiO3 films was the substrate temperature. The activation energy for the epitaxy formation was about 0.92eV. Lower gas pressure and RF input power were favorable for the formation of epitaxial c-axis orientation. It was also found that the optimum oxygen content in Ar gas was 10% to obtain the stoichiometric PbTiO3 composition.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.108-115
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• 2018

The increasing demands for three-dimensional (3D) electronic and optoelectronic devices have triggered interest in epitaxial growth of 3D semiconductor materials. However, most of the epitaxially-grown nano- and micro-structures available so far are limited to certain forms of crystal arrays, and the level of control is still very low. In this review, we describe our latest progress in 3D epitaxy of oxide and nitride semiconductor crystals. This paper covers issues ranging from (i) low-temperature solution-phase synthesis of a well-regulated array of ZnO single crystals to (ii) systematic control of the axial and lateral growth rate correlated to the diameter and interspacing of nanocrystals, as well as the concentration of additional ion additives. In addition, the critical aspects in the heteroepitaxial growth of GaN and InGaN multilayers on these ZnO nanocrystal templates are discussed to address its application to a 3D light emitting diode array.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.463-465
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• 2002

In order to increase perpendicular magnetic anisotropy of magnetic layer and prepare magnetic recording layer with a good quality by epitaxial growth between magnetic layer and, we prepared Co$\_$77/Cr$\_$20/Ta$_3$/Si doublelayer for perpendicular magnetic recording media which was promoted as next generation recording media on slide glass substrate. The thickness of magnetic layer and Underlayer were varied from 20 to 100 nm and 5 to 100 m, respectively. The surface morphology and crystal structure of the CoCrTa/Si film were examined with XRD and AFM. Prepared thin films showed improvement of dispersion angle of c-axis orientation Δ$\theta$$\_$50/ caused by inserting amorphous Si underlayer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.285-288
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• 2004

탄화규소 기판의 에피 박막결함으로는 dislocation, micropipe, pin-hole 및 에피층 표면의 여러 가지 결함들이 있다. 이러한 결함들이 탄화규소 쇼트키 다이오드의 항복전압과 어떠한 상관관계가 존재하는지 알아 보기 위해 탄화규소 쇼트키 다이오드를 제작하고, 제작된 소자의 항복전압을 측정하였다. 에피 박막내의 결함 분포를 알아보기 위해 항복전압 측정후 KOH 용액을 이용한 SiC의 에칭을 수행하였으며, 제작된 여러소자들에 대해 항복전압의 분포도와 결함 분포도를 작성, 비교 관찰하였다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.4
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• pp.17-23
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• 1984

A model analysis of pattern shift in the epitaxial growth of silicon on (111) substrates was performed. The growth rate anisotropy was considered as the most important affecting factor of pattern shift, and for the model establishment the off angle of the substrate and the process temperature were taken as the variables. We derived a theoretical equation of pattern shift by assuming the growth rate anisotropy as the trigonometric sine function of the off angle of the substrate and defining the growth rate anisotropy factor related to the process temperature. The pattern shift ratio calculated by this model had the same tendency with the experimental ones, which, however, were about twice greater than those. It was supposed that this discrepailcy was due to the second order affecting factor such as facetting and step broadening which had been exluded in model establishment.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.121-126
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• 1998

A numerical optimization procedure is developed to find the inlet velocity profile that yields the most uniform epitaxial layer in a vertical MOCVD reactor. It involves the solution of fully elliptic equations of motion, temperature, and concentration; the finite volume method based on SIMPLE algorithm has been adopted to solve the Navier-Stokes equations. The overall optimization process is highly nonlinear and has been efficiently treated by the sequential linear programming technique that breaks the non-linear problem into a series of linear ones. The optimal profile approximated by a 6th-degree Chebyshev polynomial is very successful in reducing the spatial non-uniformity of the growth rate. The optimization is particularly effective to the high Reynolds number flow. It is also found that a properly constructed inlet velocity profile can suppress the buoyancy driven secondary flow and improve the growth-rate uniformity.