Ji Won Yang

Morphology

Crystal (programming language)

10.3938/jkps.58.873

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Citations (2)

The Light Extraction Efficiency of p-GaN Patterned InGaN/GaN Light-Emitting Diodes Fabricated by Size-Controllable Nanosphere Lithography

Japanese Journal of Applied Physics (2011)

Jae In Sim Byoung Gyu Lee Ji Won Yang Hyung-do Yoon Tae Geun Kim

The authors present a light extraction improvement at a low operation voltage from p-GaN patterned InGaN/GaN light-emitting diodes (LEDs) fabricated using size-controllable nanosphere lithography and subsequent inductively coupled plasma etching. A 300-nm polystyrene (PS) nanosphere array was used as an etching mask in order to produce ordered pillar patterns on the p-GaN layer, during which the top and bottom size of the pillars were tailored to optimize the electrical and optical properties by varying the diameter of the PS nanosphere masks. Three LEDs, without patterns and with pillar patterns of 210 nm and 240 nm diameter, were compared with each other, in which the LED with 240 nm diameter pillar patterns showed the highest output power (32.6% higher than that of the LEDs without patterns) in both its electroluminescence and photoluminescence measurements.

Nanosphere lithography

Wide-bandgap semiconductor

10.7567/jjap.50.102101

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Effects of Nanometer-Scale Photonic Crystal Structures on the Light Extraction From GaN Light-Emitting Diodes

IEEE Journal of Quantum Electronics (2010)

Young Chul Shin Dongho Kim Dong Ju Chae Ji Won Yang Jae In Shim

This paper reports on the effect of nanometer-scale photonic crystal structures on the enhancement of the light extraction in GaN light-emitting diodes. Photonic crystals with hole or pillar-patterned structures with lattice constants of 460, 600, 750, and 920 nm are fabricated on indium-doped tin oxide (ITO) electrodes and/or p-GaN layers using laser holography and reactive ion etching. It is found that the light extraction efficiency depends strongly on the distance between the photonic crystal and the active layer, as well as the lattice constant for both structures. Photonic crystal light-emitting diodes (LEDs) with a lattice constant of 750 nm and hole depths of 260 nm in the ITO layer show an increase in light extraction of up to 32%, compared to conventional LEDs, without degradation in the electrical properties while a maximum enhancement of 26% is obtained from the device with a lattice constant of 460 nm and pillar heights of 60 nm on the p-GaN layer. The dependence of the extraction efficiency on the lattice constant is also calculated using a 3-D finite-difference time-domain method and compared with experimental results.

Lattice constant

Indium tin oxide

Indium gallium nitride

10.1109/jqe.2010.2049827

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Citations (32)

Hot Electrons and Holes in Highly Photoexcited GaN Epilayers

physica status solidi (b) (1999)

A. Žukauskas Г. Тамулайтис R. Gaška M. S. Shur M. Asif Khan

In GaN epilayers an increase of the carrier temperature was deduced from the luminescence spectra under intense quasi-steady-state photogeneration. To account for the measured dependence of the electron temperature on the excitation power density, all relevant mechanisms of the nonequilibrium-phonon production were considered. Finally, theoretical modeling yielded strong implications that, contrary to electrons, hot photogenerated holes maintain no Maxwellian distribution function above the threshold for the optical phonon emission.

10.1002/(sici)1521-3951(199911)216:1<495::aid-pssb495>3.0.co;2-0

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Citations (6)

The Light Extraction Efficiency of p-GaN Patterned InGaN/GaN Light-Emitting Diodes Fabricated by Size-Controllable Nanosphere Lithography

Japanese Journal of Applied Physics (2011)

Jae In Sim Byoung Gyu Lee Ji Won Yang Hyung-do Yoon Tae Geun Kim

The authors present a light extraction improvement at a low operation voltage from p-GaN patterned InGaN/GaN light-emitting diodes (LEDs) fabricated using size-controllable nanosphere lithography and subsequent inductively coupled plasma etching. A 300-nm polystyrene (PS) nanosphere array was used as an etching mask in order to produce ordered pillar patterns on the p-GaN layer, during which the top and bottom size of the pillars were tailored to optimize the electrical and optical properties by varying the diameter of the PS nanosphere masks. Three LEDs, without patterns and with pillar patterns of 210 nm and 240 nm diameter, were compared with each other, in which the LED with 240 nm diameter pillar patterns showed the highest output power (32.6% higher than that of the LEDs without patterns) in both its electroluminescence and photoluminescence measurements.

Nanosphere lithography

10.1143/jjap.50.102101

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Citations (7)

Optical properties of InGaAs/GaAs quantum chains

Acta Physica Sinica (2008)

Baorui Wang Zheng Sun Xu Zhong-Ying Sun Bao-Quan Ji Won Yang

We have investigated the steady-state and transient optical properties of InGaAs/GaAs quantum chains and found that the photoluminescence (PL) decay time exhibits a strong photon energy dependence. It increases with the decrease of the emission energy. It is also found that the PL decay time increases with the excitation power. When the excitation power is large enough the PL decay time tends to be saturated. All these experimental results show that there is a strong carrier coupling along the chain direction in the quantum dot chain structure. The polarization PL measurements further confirm the carrier transfer process along the chain direction.

Photon energy

Transient (computer programming)

10.7498/aps.57.1908

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Citations (2)

Effects of external magnetic field on the effective g factor of (Ga，Mn)As

Acta Physica Sinica (2008)

Rong Zhou Sun Bao-Quan Ruan Xue-Zhong Huadong Gan Ji Won Yang

With the help of time resolved magneto-optic Kerr rotation measurements， the optically induced spin precession in heavily doped diluted magnetic semiconductor Ga0.937Mn0.063As was observed. It was found that the effective g factor increases with increasing magnetic field， which is attributed to the magnetic-field-induced increase of the density of the non-localized holes. Those free holes will couple with the localized magnetic ions by p-d interactions， leading to the formation of spontaneous magnetization in Ga0.937Mn0.063As， which in turn to the enhancement of the effective g factor.

Precession

Magnetic semiconductor

10.7498/aps.57.5244

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Citations (1)

{001}/{101} facets co-exposed TiO2 microsheet arrays with Lanthanum doping for enhancing photocatalytic CO2 reduction

Journal of Materials Science Materials in Electronics (2020)

Xin Liu Ji Won Yang Lanqing Hu Qianqian Shen Qi Li

Lanthanum

Hydrothermal Synthesis

10.1007/s10854-020-04479-0

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Citations (7)

Cr-Doped InAs Self-Organized Diluted Magnetic Quantum Dots with Room-Temperature Ferromagnetism

Chinese Physics Letters (2007)

Zheng Yuhong Zhao Jian-Hua Bi Jing-Feng Wang Wei-Zhu Ji Won Yang

Cr-doped InAs self-organized diluted magnetic quantum dots (QDs) are grown by low-temperature molecular-beam epitaxy. Magnetic measurements reveal that the Curie temperature of all the InAs:Cr QDs layers with Cr/In flux ratio changing from 0.026 to 0.18 is beyond 400 K. High-resolution cross sectional transmission electron microscopy images indicate that InAs:Cr QDs are of the zincblende structure. Possible origins responsible for the high Curie temperature are discussed.

10.1088/0256-307x/24/7/092

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Citations (19)

Oxidative N-Debenzylation of N-Benzyl-N-substituted Benzylamines Catalyzed by Cytochrome P450

Bulletin of the Korean Chemical Society (2004)

Sung Soo Kim Gang Lin Ji Won Yang

Cytochrome P450 (P450)/$O_2$/NADPH engender electron transfer reaction of N-benzyl-N-substituted benzylamines to yield corresponding radical cation 1 that is simultaneously converted into 2 and 3. Subsequently, expulsion of proton and hydroxylation yielding a-hydroxylamines are followed by formation of benzaldehydes and benzylamines.

Hydroxylation

10.5012/bkcs.2004.25.2.249

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Citations (4)

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