Browsing by Author "Sou, Kuok-Pan"

Now showing 1 - 8 of 8

Electrically driven green, olivine, and amber color nanopyramid light emitting diodes
(2013-10-07)
Chang, Shih-Pang
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Chang, Jet-Rung
;
Sou, Kuok-Pan
;
Liu, Mei-Chun
;
Cheng, Yuh-Jen
We report the fabrication and studies of electrically driven green, olivine, and amber color nanopyramid GaN light emitting diodes (LEDs). InGaN/GaN multiple quantum wells (MQWs) were grown on the nanopyramid semipolar facets. Compared with the commonly used (0001) c-plane MQWs, the semipolar facet has lower piezoelectric field, resulting in much faster radiative recombination efficiency. This is important for high In content MQWs. The measured internal quantum efficiencies for green, olivine, and amber color LED are 30%, 25%, and 21%, respectively. The radiative and non-radiative lifetime of the semipolar MQWs are also investigated. (C) 2013 Optical Society of America
InGaN/GaN multiple-quantum-well nanopyramid-on-pillar light-emitting diodes
(2015-04-01)
Li, Yun-Jing
;
Chang, Jet-Rung
;
Chang, Shih-Pang
;
Sou, Kuok-Pan
;
Cheng, Yuh-Jen
We report the study of an electrically driven nanopyramid-on-pillar green light-emitting diode (LED). The pyramid-on-pillar nanostructure was fabricated by top-down etching from a GaN template, followed by epitaxial regrowth. High-In-content InGaN/GaN multiple quantum wells (MQWs) were grown on semipolar pyramid and nonpolar pillar surfaces. The measured radiative lifetimes of MQWs on these two surfaces were 2 orders of magnitude shorter than that of a conventional c-plane (0001) MQW owing to their lower polarization field. Electrical injection performance was also demonstrated and discussed. (C) 2015 The Japan Society of Applied Physics
Lasing action in gallium nitride photonic quasicrystal nanorod arrays
(2012)
Chang, Shih-Pang
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Sou, Kuok-Pan
;
Chang, Jet-Rung
;
Cheng, Yuh-Jen
;
Li, Yuh-Jing
We report the observation of lasing action from optically pumped gallium nitride nanorod arrays in a quasicrystal pattern. The nanorods were fabricated from a GaN substrate by nanoimprint patterned etching, followed by epitaxial regrowth to form crystalline facets. The imprint was a 12-fold symmetric quasicrystal pattern. The regrowth grew a multiple quantum well core-shell structure on nanorods. The cathodoluminescent emission of quantum wells red shifts from the bottom to top region of nanorod. Under optical pumping, multiple lasing peaks were observed. The lasing modes formed by 12-fold symmetric photonic quasicrystal nanorod arrays are discussed.
Lasing action in gallium nitride quasicrystal nanorod arrays
(2012-05-21)
Chang, Shih-Pang
;
Sou, Kuok-Pan
;
Chen, Chieh-Han
;
Cheng, Yuh-Jen
;
Huang, Ji-Kai
We report the observation of lasing action from an optically pumped gallium nitride quasicrystal nanorod arrays. The nanorods were fabricated from a GaN substrate by patterned etching, followed by epitaxial regrowth. The nanorods were arranged in a 12-fold symmetric quasicrystal pattern. The regrowth grew hexagonal crystalline facets and core-shell multiple quantum wells (MQWs) on nanorods. Under optical pumping, multiple lasing peaks resembling random lasing were observed. The lasing was identified to be from the emission of MQWs on the nanorod sidewalls. The resonant spectrum and mode field of the 12-fold symmetric photonic quasicrystal nanorod arrays is discussed. (C) 2012 Optical Society of America
Low efficiency droop of InGaN/GaN blue LEDs with super-lattice active structure
(2012)
Chang, Shih-Pang
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Sou, Kuok-Pan
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Chang, Jet-Rung
;
Cheng, Yuh-Jen
;
Li, Yuh-Jing
We report the efficiency droop behaviors of InGaN/GaN blue LEDs with different thickness of GaN quantum barriers (QBs). The droop percentage from efficiency peak to 70 A/cm(2) is only about 10% as reducing the thickness of GaN QBs from 104 angstrom to 33 angstrom. A less carrier localization has been observed from wavelength dependent time resoled photoluminescence measurement as reducing the thickness of GaN QBs. The alleviation of droop percentage may due to more uniform distribution of electron and hole carrier in the active region, which resulted from super-lattice (SL) like active structure. The crystalline quality does not become worse from the results of v-pits density even thickness of GaN QBs is as low as 33 angstrom. The SL like active structure could be a potential structure to alleviate the efficiency droop for the application of solid state general lighting.
Photoluminescent Study of High Indium Content Nanopyramid Light Emitting Diodes
(2013)
Chang, Shih-Pang
;
Chang, Jet-Rung
;
Sou, Kuok-Pan
;
Li, Yun-Jing
;
Cheng, Yuh-Jen
The radiative and non-radiative lifetime of high In content nanopyramid GaN LEDs are investigated by time resolved and temperature dependent photoluminescent measurement. The radiative recombination efficiency is much improved compared with the conventional c-plane LED.
Room temperature ultraviolet GaN metal-coated nanorod laser
(2013-11-04)
Hsu, Yu-Cheng
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Sou, Kuok-Pan
;
Chang, Shih-Pang
;
Hsu, Kung-Shu
;
Shih, M. H.
This study demonstrates a room-temperature ultraviolet GaN/Al nanorod (NR) metal laser with an optimized sidewall. A wet-chemical etching process with potassium hydroxide was used to control the GaN NR sidewall angle and polish the NR surface. The lasing action was observed near a wavelength of 365 nm with a low threshold power density of 5.2 mJ/cm(2). The high-quality factor (Q) surface plasmon lasing modes were characterized with experiments and three-dimensional finite-element method simulations. We also studied the optical modes in GaN metal-coated NR with and without an Al layer and verified the metal layer is necessary for high-Q resonant modes. (c) 2013 AIP Publishing LLC.
The Crystalline and Optical Properties of (11(2)over-bar2) Semipolar GaN and InGaN/GaN MQWs on (1(1)over-bar00) M-Sapphire
(2013-01-01)
Li, Yun-Jing
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Chang, Shih-Pang
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Sou, Kuok-Pan
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Chang, Jet-Rung
;
Chang, Ruey-Wen
We report the growth temperature effect on the crystalline and optical properties of (11 (2) over bar2) semipolar GaN and InGaN/GaN MQWs. It shows that a lower growth temperature at 1020 degrees C produces better crystalline and optical properties.