• 한국결정성장학회지
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• 제23권6호
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• pp.279-282
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• 2013

최근 관심이 높아지고 있는 GaN, SiC 단결정과 함께 자외선 LED 및 전력 반도체 용 기판 소재로서 응용성이 높은 질화갈륨(AlN, Aluminum Nitride) 단결정을 성장하였다. 아직 상용화된 AlN 기판은 없지만, 단결정 성장에 대한 연구가 이루어지고 있다. 본 연구에서는 국내 최초로 AlN 단결정의 성장 결과 직경 약 8 mm의 결정을 성장하였다. 성장된 단결정은 광학현미경으로 관찰하였으며, DCXRD를 통하여 결정성을 평가한 결과를 보고하고자 한다.

• 한국정밀공학회지
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• 제25권9호
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• pp.32-37
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• 2008

Freestanding hydride vapor phase epitaxy grown GaN(Gallium Nitride) substrates subjected to various polishing methods were characterized for their surface and subsurface conditions, Although CMP(Chemical Mechanical Polishing) is one of the best approaches for reducing scratches and subsurface damages, the removal rate of Ga-polar surface in CMP is insignificant($0.1{\sim}0.3{\mu}m$/hr) as compared with that of N-polar surface, Therefore, conventional MP(Mechanical Polishing) is commonly used in the GaN substrate fabrication process, MP of (0001) surface of GaN has been demonstrated using diamond slurries with different abrasive sizes, Diamond abrasives of size ranging from 30nm to 100nm were dispersed in ethylene glycol solutions and mineral oil solutions, respectively. Significant change in the surface roughness ($R_a$ 0.15nm) and scratch-free surface were obtained by diamond slurry of 30nm in mean abrasive size dispersed in mineral oil solutions. However, MP process introduced subsurface damages confirmed by TEM (Transmission Electronic Microscope) and PL(Photo-Luminescence) analysis.

• 대한기계학회논문집B
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• 제31권3호
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• pp.225-233
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• 2007

The growth of GaN on the patterned substances has proven favorable to achieve thick, crack-free GaN layers. In this paper, numerical modeling of transport and reaction of species is performed to estimate the growth rate of GaN from tile reaction of TMG(trimethly-gallium) and ammonia. GaN growth rate was estimated through the model analysis including the effect of species velocity, thermal convection and chemical reaction, and thermal condition for the uniform deposition was to be presented. The effect of shape and construction of microscopic pattern was also investigated using a simulator to perform surface analysis, and a review was done on the quantitative thickness and shape in making GaN layer on the pattern. Quantitative analysis was especially performed about the shape of reactor geometry, periodicity of pattern and flow conditions which decisively affect the quality of crystal growth. It was found that the conformal deposition could be obtained with the inclination of trench ${\Theta}>125^{\circ}$. The aspect ratio was sensitive to the void formation inside trench and the void located deep in trench with increased aspect ratio.

• 한국군사과학기술학회지
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• 제13권6호
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• pp.1071-1079
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• 2010

This paper describes the design and fabrication of a high-efficiency GaN HEMT(Gallium Nitride High-electron Mobility Transistor) Pallet power amplifier module for S-band phased array radar applications. Pallet amplifier module has a series 2-cascaded power amplifier and the final amplification-stage consists of balanced GaN HEMT transistor. In order to achieve high efficiency characteristic of pallet power amplifier module, all amplifiers are designed to the switching-mode amplifier. We performed with various PRF(Pulse Repetition Frequency) of 1, 10, 100 and 1000Hz at a fixed pulse width of $100{\mu}s$. In the experimental results, the output power, gain, and drain efficiency(${\eta}_{total}$) of the Pallet power amplifier module are 300W, 33dB, and 51% at saturated output power of 2.9GHz, respectively.

• 한국전기전자재료학회논문지
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• 제32권6호
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• pp.444-447
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• 2019

It was proven that the light outputs of blue GaN-based light-emitting diodes (LEDs) was seriously influenced by the application of external stress. We have simulated the wave function overlap of an electron and hole, which are significantly reduced by the development of stress. Consequently, its internal quantum efficiency decreased from 67.0% to 37.5%. To experimentally investigate the effect of stress, we designed and prepared a special zig system. By applying external tensile stress to compensate for the compressive stress innately developed in Blue LEDs, it was found that the optical output was greatly enhanced from 83.1 mcd to 117.2 mcd at a current of 100 mA, an increase of approximately 41%. In contrast, when the compressive stress is developed more by external compressive stress, we observed that the light output power was reduced from 89.0 mcd to 80.7 mcd, a decrease of approximately 9.3%.

• 한국결정성장학회지
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• 제34권2호
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• pp.61-65
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• 2024

HVPE(Hydride vapor phase epitaxy) 공법은 기체상의 원료를 사용하여 박막 또는 단결정을 제조하는 공법이다. 화학적 기상증착법의 원리를 적용하여 난용융성 또는 고융점의 물질의 단결정을 성장할 수 있는 공법으로서, 질화갈륨(GaN) 단결정을 얻을 수 있는 공법 중 하나이다. 최근 동 공법을 이용하여 질화알루미늄(AlN) 단결정을 성장하고자 하는 연구가 많이 수행되어져 왔으나, 아직은 좋은 결과를 얻지 못하고 있다. 본 연구에서는 AlN 단결정을 HVPE 공법으로 성장하고자 하였다. 성장 공정에서 질소를 운송가스(Carrior gas)로 사용하였으며, 질소(N2)의 양의 변화에 따른 성장 결과를 고찰하여 보았다. 질소의 양이 증가함에 따른 성장 결정의 변화 양상을 확인할 수 있었다. 성장된 AlN 단결정의 형상을 광학 현미경을 사용하여 관찰하였고, 이중결정 X선 회절 분석(DCXRD, Double crystal X-ray diffractometry)을 이용하여, AlN 결정의 생성을 확인함과 동시에 성장된 단결정의 결정성도 알아보았다.

• 한국진공학회지
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• 제20권4호
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• pp.271-275
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• 2011

본 논문은 고휘도 발광소자의 특성을 높이기 위한 p-GaN 박의 홀농도 향상을 연구하였다. 우리는 metal organic chemical vapor deposition 법을 이용하여 Antimony (Sb)가 p-GaN의 홀농도 향상에 도움을 주는 것을 확인하였다. Atomic force microscope 측정을 통해 Sb가 계면활성제처럼 역할을 함으로써 p-GaN의 2차원 성장이 촉진됨을 알 수 있었다. 또한 X-ray diffraction 결과 [002] 면과 [102] 면의 반폭치가 Sb 도핑과 함께 줄어드는 것을 통해 Edge과 Screw 전위의 감소와 photoluminescence 결과에서 450~500 nm 청색 파장 영역에서 발광의 세기가 현저히 줄어드는 것으로 보아 질소 공극이 감소되는 것이 홀농도 향상의 주된 원임임을 알 수 있었다. Trimethylantimony가 10 ${\mu}mol/min$일 때 홀농도는 최대가 되었고 그때 홀농도는 $5.4{\times}10^{17}cm^{-3}$이었다.

• 한국전자파학회논문지
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• 제28권9호
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• pp.685-697
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• 2017

본 논문에서는 탐색 레이다에서 사용되는 C-대역의 고출력전력증폭장치 및 구성품의 설계, 제작과 측정에 대하여 기술하였다. 반도체 소자인 GaN(질화갈륨)을 적용하여 반도체전력증폭조립체를 설계 및 제작하였고, 설계 제작된 도파관 형태의 송신신호결합조립체를 통해 병렬로 구성된 반도체전력증폭조립체의 송신신호 출력을 결합하여 고출력 송신신호 출력을 발생한다. 제작된 고출력전력증폭장치는 C-대역 500 MHz 대역폭, 최대 10.5 % 듀티, 송신펄스폭 $0.0{\sim}000{\mu}s$에서 송신출력 44.98 kW(76.53 dBm) 이상이다.

• Tribology and Lubricants
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• 제35권5호
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• pp.274-285
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• 2019

Chemical mechanical polishing (CMP), which is a material removal process involving chemical surface reactions and mechanical abrasive action, is an essential manufacturing process for obtaining high-quality semiconductor surfaces with ultrahigh precision features. Recent rapid growth in the industries of digital devices and semiconductors has accelerated the demands for processing of various substrate and film materials. In addition, to solve many issues and challenges related to high integration such as micro-defects, non-uniformity, and post-process cleaning, it has become increasingly necessary to approach and understand the processing mechanisms for various substrate materials and abrasive particle behaviors from a tribological point of view. Based on these backgrounds, we review recent CMP R&D trends in this study. We examine experimental and analytical studies with a focus on substrate materials and abrasive particles. For the reduction of micro-scratch generation, understanding the correlation between friction and the generation mechanism by abrasive particle behaviors is critical. Furthermore, the contact stiffness at the wafer-particle (slurry)-pad interface should be carefully considered. Regarding substrate materials, recent research trends and technologies have been introduced that focus on sapphire (${\alpha}$-alumina, $Al_2O_3$), silicon carbide (SiC), and gallium nitride (GaN), which are used for organic light emitting devices. High-speed processing technology that does not generate surface defects should be developed for low-cost production of various substrates. For this purpose, effective methods for reducing and removing surface residues and deformed layers should be explored through tribological approaches. Finally, we present future challenges and issues related to the CMP process from a tribological perspective.

• 전기화학회지
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• 제17권1호
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• pp.1-6
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• 2014

본 총설은 질화 갈륨(GaN)을 이용한 광전기화학적 물분해 연구에 대해 정리하였다. GaN는 화학적으로 안정하고 에너지 띠간격 조절이 자유롭다는 장점으로 최근 물분해를 위한 새로운 광전극 물질로 연구되고 있다. 다른 화합물 반도체 물질은 강산 혹은 강염기 전해액에 의해 쉽게 부식되기 때문에 광산화전극(photoanode)으로는 사용이 어려운 반면, n형 GaN는 뛰어난 안정성 덕분에 산화 분위기의 산소 발생 전극으로도 활용이 가능하다. 또한, 최근에는 p형 GaN을 환원전극으로 이용한 광전극에 대한 연구도 보고되었다. GaN 물질이 실제 응용되기 위해 필요한 과제들에 대해 다루었다.