• Current Optics and Photonics
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• 제1권4호
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• pp.358-363
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• 2017

In this study, we present a detailed investigation of luminescence properties of a blue light-emitting diode using InGaN/GaN (indium component is 17.43%) multiple quantum wells as the active region grown on patterned sapphire substrate by low-pressure metal-organic chemical vapor deposition (MOCVD). High-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman scattering (RS) and photoluminescence (PL) measurements are employed to study the crystal quality, the threading dislocation density, surface morphology, residual strain existing in the active region and optical properties. We conclude that the crystalline quality and surface morphology can be greatly improved, the red-shift of peak wavelength is eliminated and the superior blue light LED can be obtained because the residual strain that existed in the active region can be relaxed when the LED is grown on patterned sapphire substrate (PSS). We discuss the mechanisms of growing on PSS to enhance the superior luminescence properties of blue light LED from the viewpoint of residual strain in the active region.

• 한국광학회:학술대회논문집
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• 한국광학회 1990년도 제5회 파동 및 레이저 학술발표회 5th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.115-120
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• 1990

The spectroscopic properties of Cr3+-doped sapphire and Ti3+-doped sapphire fibers are reported. Tensile stress produces blue shifts of the R lines and changes in their radiative lifetimes and integrated intensities which can be correlated to stress-induced changes of the crystal-field parameters in a Cr3+-doped sapphire fiber. A net red shift of the zero phonon fluorescence line of 2Eg state and a decrease of the splittings of 2T2g state with uniaxial stress are observed in a Ti3+-doped sapphire. In excitation spectra the two peaks from the 2Eg state are shifted to the blue with different rates. The changes are attributed to the stress-induced changes of crystal field and Jahn-Teller effect.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2003년도 춘계학술대회 발표 논문집
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• pp.18-22
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• 2003

The sapphire wafers for blue light emitting devices were manufactured by the implementation of the surface machining technology based on micro-tribology. This process has been performed by grinding, lapping and polishing. The surfaces of sapphire wafers were mechanically affected by residual stress and surface default. This mechanical stress and strain can be cured by thermal anneal ing process. The sapphire crystalline wafers were annealed at $1100~1400^{\circ}C$ and then characterized by double crystal X-ray diffraction. The sample showed good quality of crystalline wafer surface wi th full width at hal f maximum of 16 arcsec for the 4-hour heat-treatment at $1300^{\circ}C$.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.224-225
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• 2000

Transparent and hard materials such as sapphire are used for many industrial applications as optical windows, hard materials on mechanical contact against abrasion, and substrate materials for opto-electronic semiconductor devices such as blue LED and blue LD etc. The materials should be cut along the proper shapes possible to be used for each application. In case of blue LED, the blue LED wafer should be cut to thousands of blue LED pieces at the final stage of the manufacturing process. The process of cutting the wafer is usually divided into two steps. The wafer is scribed along the proper shapes in the first step. It is inserted between transparent flexible sheets for easy handling. And then, it is broken and split in the next step. Harder materials such as diamonds are usually used to scribe the wafer, while it has a problem of low depth of scribing and abrasion of the harder material itself. The low depth of scribing can induce failure in breaking the wafer along the scribed line. It was also known that the expensive diamond tip should be replaced frequently for the abrasion. (omitted)

• 한국정밀공학회지
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• 제21권2호
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• pp.218-223
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• 2004

The sapphire wafers for blue light emitting devices were manufactured by the implementation of the surface machining technology based on micro-tribology. This process has been performed by Micro-lapping process. The sapphire crystalline wafers were characterized by double crystal X-ray diffraction. The sample quality of crystalline sapphire wafer at surface has a full width at half maximum of 250 arcsec. This value at the surface sapphire wafer surfaces indicated 0.12${mu}m$ sizes. Surfaces of sapphire wafers were mechanically affected by residual stress and surface default. As a result, the value of surface roughness of sapphire wafers measured by AFM(Atom Force Microscope) was 2.1nm.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.82-85
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• 2003

The sapphire wafers for blue light emitting devices were manufactured by the implementation of the surface machining technology based on micro-tribology. This process has been performed by Micro-lapping process. The sapphire crystalline wafers were characterized by DCXD(Double Crystal X-ray Diffraction). The sample quality of crystalline sapphire wafer at surface has a FWHM(Full Width at Half Maximum) of 250 arcsec. This value at the sapphire wafer surfaces indicated 0.12${\mu}{\textrm}{m}$ sizes. Surfaces of sapphire wafers were mechanically affected by residual stress and surface default. Also Surfaces roughness of sapphire wafers were measured 2.1 by AFM(Atom Force Microscope).

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 추계종합학술대회
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• pp.656-661
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• 2002

라이다 광원용 다중통과 Ti-sapphire 증폭기를 각도다중 방식으로 설계하여 출력에너지 및 스펙트럼 특성을 개선하였다. 2-단의 다중통과 증폭기에서 파장이 790nm 일 때, 42mJ의 출력에너지와 21dB의 증폭이득 및 26%의 출력효율을 얻었으며, 715~930nm이 파장가변 영역에서 스펙트럼 선폭은 0.05$cm^{-1}$ / 이하였다. 780nm의 파장에서 35%의 SHG 변환효율과 390nm의 파장에서 13%의 THG 변환효율을 각각 얻었다. 결과적으로 240~306nm의 자외영역과 360~460nm의 deep-blue 영역에서 연속적으로 파장을 가변시킬 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 기술교육전문연구회
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• pp.31-34
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• 2003

The sapphire wafers for blue light emitting devices were manufactured by the implementation of the surface machining technology based on micro-tribology. This process has been performed by chemical and mechanical polishing(CMP) process. The sapphire crystalline wafers were characterized by double crystal X-ray diffraction. The sample quality of sapphire crystalline wafer at surfaces has a full width at half maximum 89 arcses. The surfaces of sapphire wafers were mechanically affected by residual stress and surface default. Sapphire wafers's waveness has higher abrasion rate in the edge of the wafer than its center due to Newton's Ring interference.

• 대한기계학회논문집A
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• 제28권1호
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• pp.85-91
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• 2004

The sapphire wafers for blue light emitting devices were manufactured by the implementation of the surface machining technology based on micro-tribology. This process has been performed by chemical and mechanical polishing process. The sapphire crystalline wafers were characterized by double crystal X-ray diffraction. The sample quality of sapphire crystalline wafer at surfaces has a full width at half maximum of 89 arcsec. The surfaces of sapphire wafer were mechanically affected by residual stress during the polishing process. The wave pattern of optical interference of sapphire wafer implies higher abrasion rate in the edge of the wafer than its center from the Newton's ring.

• 한국정밀공학회지
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• 제22권2호
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• pp.46-52
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• 2005

The sapphire wafer was polished by the implementation of the surface machining technology based on nano-tribology, The removal process has been performed by grinding, lapping and chemical-mechanical polishing. For the chemical mechanical polishing process, the chemical reaction between the slurry and sapphire wafer was investigated in terms of the change of Zeta-potential between two materials. The Zeta-potential was -4.98 mV without the slurry in deionized water and was -37.05 mV for the slurry solution. By including the slurry into the deionized water the Zeta-potential -29.73 mV, indicating that the surface atoms of sapphire become more repulsive to be easy to separate. The average roughness of the polished surface of sapphire wafer was ranged to 1∼4$\AA$.