Browsing by Author "Shen, Kun-Ching"

Now showing 1 - 5 of 5

Deep-Ultraviolet Hyperbolic Metacavity Laser
(2018-05-24)
Shen, Kun-Ching
;
Ku, Chen-Ta
;
Hsieh, Chiieh
;
Kuo, Hao-Chung
;
Cheng, Yuh-Jen
Given the high demand for miniaturized optoelectronic circuits, plasmonic devices with the capability of generating coherent radiation at deep subwavelength scales have attracted great interest for diverse applications such as nanoantennas, single photon sources, and nanosensors. However, the design of such lasing devices remains a challenging issue because of the long structure requirements for producing strong radiation feedback. Here, a plasmonic laser made by using a nanoscale hyperbolic metamaterial cube, called hyperbolic metacavity, on a multiple quantum-well (MQW), deep-ultraviolet emitter is presented. The specifically designed metacavity merges plasmon resonant modes within the cube and provides a unique resonant radiation feedback to the MQW. This unique plasmon field allows the dipoles of the MQW with various orientations into radiative emission, achieving enhancement of spontaneous emission rate by a factor of 33 and of quantum efficiency by a factor of 2.5, which is beneficial for coherent laser action. The hyperbolic metacavity laser shows a clear clamping of spontaneous emission above the threshold, which demonstrates a near complete radiation coupling of the MQW with the metacavity. This approach shown here can greatly simplify the requirements of plasmonic nanolaser with a long plasmonic structure, and the metacavity effect can be extended to many other material systems.
Enhanced Radiative Emission of MQW by Resonant Modes of Hyperbolic Metamaterial Resonator
(2019-01-01)
Shen, Kun-Ching
;
Hsu, Lung-Hsing
;
Tsai, Din Ping
;
Kuo, Hao-Chung
;
Lin, Chien-Chung
We report the use of resonant modes of a hyperbolic metamaterial cube made of multiple metal/dielectric layer structure to enhance the radiative emission of multiple quantum wells. The mode analysis and photoluminescence will be discussed. (C) 2019 The Author(s)
High-Efficiency and Crack-Free InGaN-Based LEDs on a 6-inch Si (111) Substrate With a Composite Buffer Layer Structure and Quaternary Superlattices Electron-Blocking Layers
(2014-05-01)
Li, Zhen-Yu
;
Lee, Chia-Yu
;
Lin, Da-Wei
;
Lin, Bing-Cheng
;
Shen, Kun-Ching
In this paper, a composite buffer layer structure (CBLS) with multiple AlGaN layers and grading of Al composition/u-GaN1/(AlN/GaN) superlattices/u-GaN2 and InAlGaN/AlGaN quaternary superlattices electron-blocking layers (QSLs-EBLs) are introduced into the epitaxial growth of InGaN-based light-emitting diodes (LEDs) on 6-inch Si (111) substrates to suppress cracking and improve the crystalline quality and emission efficiency. The effect of CBLS and QSLs-EBL on the crystalline quality and emission efficiency of InGaN-based LEDs on Si substrates was studied in detail. Optical microscopic images revealed the absence of cracks and Ga melt-back etching. The atomic force microscopy images exhibited that the root-meansquare value of the surface morphology was only 0.82 nm. The full widths at half maxima of the (0002) and (1012) reflections in the double crystal X-ray rocking curve were similar to 330 and 450 arcs, respectively. The total threading dislocation density, revealed by transmission electron microscopy, was <6 x 10(8) cm(-2). From the material characterizations, described above, blue and white LEDs emitters were fabricated using the epiwafers of InGaNbased LEDs on 6-inch Si substrates. The blue LEDs emitter that comprised blue LEDs chip and clear lenses had an emission power of 490 mW at 350 mA, a wall-plug efficiency of 45% at 350 mA, and an efficiency droop of 80%. The white LEDs emitter that comprised blue LEDs chip and yellow phosphor had an emission efficiency of similar to 110 lm/W at 350 mA and an efficiency droop of 78%. These results imply that the use of a CBLS and QSLs-EBL was found to be very simple and effective in fabricating high-efficiency InGaN-based LEDs on Si for solid-state lighting applications.
Improved performance of 375 nm InGaN/AlGaN light-emitting diodes by incorporating a heavily Si-doped transition layer
(2012-01-01)
Huang, Shih-Cheng
;
Shen, Kun-Ching
;
Tu, Po-Min
;
Wuu, Dong-Sing
;
Kuo, Hao-Chung
High performance 375-nm ultraviolet (UV) InGaN/AlGaN light-emitting diodes (LEDs) was developed using a heavy Si-doping technique with metalorganic chemical vapor deposition (MOCVD). From the transmission electron microcopy (TEM) image, the dislocation density was reduced after inserting a heavily Si-doping growth mode transition layer (GMTL) between un-doped GaN layer and Si-doped Al0.02Ga0.98N contact layer. The internal quantum efficiency (IQE) of the sample with GMTL measured by power-dependent photoluminescence shows 39.4% improved compared with the sample without GMTL. When the vertical type LED chips (size: 1mmx1mm) driving by a 350-mA current, the output powers of the LEDs with and without GMTL were measured to be 286.7 mW and 204.2 mW, respectively. As much as 40.4% increased light output power was achieved. Therefore, using the GMTL to reduce dislocation defects would be a promising prospective for InGaN/AlGaN UV LEDs to achieve high internal quantum efficiency.
Study of 375 nm ultraviolet InGaN/AlGaN light-emitting diodes with heavily Si-doped GaN transition layer in growth mode, internal quantum efficiency, and device performance
(2011-12-15)
Huang, Shih-Cheng
;
Shen, Kun-Ching
;
Wuu, Dong-Sing
;
Tu, Po-Min
;
Kuo, Hao-Chung
High performance 375 nm ultraviolet (UV) InGaN/AlGaN light-emitting diodes (LEDs) were demonstrated with inserting a heavy Si-doped GaN transition layer by metal-organic chemical vapor deposition. From transmission electron microcopy (TEM) image, the dislocation densities were significantly reduced due to the existence of the heavily Si-doping growth mode transition layer (GMTL), which results in residual stress relaxation and 3D growth. The internal quantum efficiency (IQE) of the LEDs with GMTL was measured by power-dependent photoluminescence (PL) to be 40.6% higher than ones without GMTL. The GMTL leads to the superior IQE performance of LEDs not only in decreasing carrier consumption at nonradiative recombination centers but also in partially mitigating the efficiency droop tendency. When the vertical-type LED chips (size: 1 mm x 1 mm) was driven with a 350 mA injection current, the output powers of the LEDs with and without GMTL were measured to be 286.7 and 204.2 mW, respectively. A 40.4% enhancement of light output power was achieved. Therefore, using the GMTL to reduce dislocations would be a promising prospective for InGaN/AlGaN UV-LEDs to achieve high IQE. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3669377]