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Nizamoglu, S.,Sari, E.,Jong-Hyeob Baek,In-Hwan Lee,Volkan Demir, H. IEEE 2009 IEEE journal of selected topics in quantum electro Vol.15 No.4
<P>LEDs made of In<SUB>x</SUB>Ga<SUB>1-x</SUB>N and (Al<SUB>x</SUB>Ga<SUB>1-x</SUB>)<SUB>1-y</SUB>In<SUB>y</SUB>P suffer from significantly reduced quantum efficiency and luminous efficiency in the green/yellow spectral ranges. To address these problems, we present the design, growth, fabrication, hybridization, and characterization of proof-of-concept green/yellow hybrid LEDs that utilize radiative and nonradiative [Forster resonance energy transfer (FRET)] energy transfers in their colloidal semiconductor nanocrystals (NCs) integrated on near-UV LEDs. In our first NC-LED, we realize a color-converted LED that incorporate green-emitting CdSe/ZnS core/shell NCs (lambda<SUB>PL</SUB> = 548 nm) on near-UV InGaN/GaN LEDs (lambda<SUB>EL</SUB> = 379 nm). In our second NC-LED, we implement a color-converted FRET-enhanced LED. For that, we hybridize a custom-design assembly of cyan- and green-emitting CdSe/ZnS core/shell NCs (lambda<SUB>PL</SUB> = 490 and 548 nm) on near-UV LEDs. Using a proper mixture of differently sized NCs, we obtain a quantum efficiency enhancement of 9% by recycling trapped excitons via FRET. With FRET-NC-LEDs, we show that it is possible to obtain a luminous efficacy of 425 lm/W opt and a luminous efficiency of 94 lm/W, using near-UV LEDs with a 40% external quantum efficiency. Finally, we investigate FRET-converted light-emitting structures that use nonradiative energy transfer directly from epitaxial quantum wells to colloidal NCs. These proof-of-concept demonstrations show that FRET-based NC-LEDs hold promise for efficient solid-state lighting in green/yellow.</P>
Efficiency enhancement of white light-emitting diodes via nano-textured silicone encapsulant.
Kim, Sang-Mook,Baek, Jong Hyeob,Hwang, Nam,Kim, Yong-Suk,Wi, Sung-Kwon,Um, Soong Ho,Jung, Gun Young American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.10
<P>We textured the surface of a silicone encapsulant to increase the extraction efficiency of white light-emitting diodes (LEDs) by using a plasma treatment. Here, the surface morphology could be controlled by changing the plasma condition and texturing morphology of the silicone encapsulant were proportion to the increased ratio of white LEDs. The luminous efficacy of the surface textured LEDs were increased 9.70% relative to the reference LED. Furthermore, the Fourier transform infrared spectroscopy spectrum showed that the chemical bonds of the silicone encapsulant were not changed by the argon-nitrogen plasma treatment, thereby reducing degradation of the optical characteristics and improving the reliability of LEDs.</P>
Sang-Mook Kim,Hwa Sub Oh,Jong Hyeob Baek,Kwang-Ho Lee,Gun Young Jung,Jae-Ho Song,Ho-Jong Kim,Byung-Jun Ahn,Dong Yanqun,Jung-Hoon Song IEEE 2010 IEEE electron device letters Vol.31 No.8
<P>The strain and piezoelectric fields in InGaN blue light-emitting diodes on a GaN layer, which is grown on a planar sapphire substrate or patterned sapphire substrates (PSSs), such as a microsized PSS and a nanosized PSS (NPSS), are investigated by micro-Raman spectroscopy and electroreflectance (ER) spectroscopy. The obtained piezoelectric field in InGaN multiple quantum wells (QWs) grown on the planar substrate is 0.83 MV/cm, and it is 0.70 MV/cm for the case of the NPSS. These results are attributed to the fact that the GaN layers on the PSSs have a smaller residual strain compared to that on the planar sapphire, and thus, strain reduction in the GaN layer can reduce the piezoelectric field in the InGaN QWs grown on top of it.</P>
단일 공정에 의한 고효율 단일모드 반도체 레이저 구조 제작을 위한 고밀도 양자 나노구조 형성
손창식,백종협,김성일,박용주,김용태,최훈상,최인훈,Son, Chang-Sik,Baek, Jong-Hyeob,Kim, Seong-Il,Park, Young-Ju,Kim, Yong-Tae,Choi, Hoon-Sang,Choi, In-Hoon 한국재료학회 2003 한국재료학회지 Vol.13 No.8
We have developed a new way of the constant growth technique to maintain a grating height of originally-etched V-groove of submicron gratings up to 1.5 $\mu\textrm{m}$ thickness by a low pressure metalorganic chemical vapor deposition. The constant growth technique is well performed on two kinds of submicron gratings that made by holography and electron (e)-beam lithography GaAs buffer layer grown on thermally deformed submicron gratings has an important role in recovering the deformed grating profile from sinusoidal to V-shaped by reducing mass transport effects. The thermal deformation effect on submicron gratings made by e-beam lithography is less than that on submicron gratings made by holography. The constant growth technique is an important step to realize complex optoelectronic devices such as one-step grown distributed feedback lasers and two-dimensional photonic crystals.