Browsing by Author "Lau, Kei-May"

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Optical and electrical properties of GaN-based light emitting diodes grown on micro and nano-scale patterned Si substrate
(2011-01-01)
Chiu, Ching-Hsueh
;
Lin, Chien-Chung
;
Deng, Dongmei
;
Kuo, Hao-Chung
;
Lau, Kei-May
We investigate the optical and electrical characteristics of the GaN-based light emitting diodes (LEDs) grown on Micro and Nano-scale Patterned silicon substrate (MPLEDs and NPLEDs). The transmission electron microscopy (TEM) images reveal the suppression of threading dislocation density in InGaN/GaN structure on nano-pattern substrate due to nanoscale epitaxial lateral overgrowth (NELOG). The plan-view and cross-section cathodoluminescence (CL) mappings show less defective and more homogeneous active quantum well region growth on nano-porous substrates. From temperature dependent photoluminescence (PL) and low temperature time-resolved photoluminescence (TRPL) measurement, NPLEDs has better carrier confinement and higher radiative recombination rate than MPLEDs. In terms of device performance, NPLEDs exhibits smaller electroluminescence (EL) peak wavelength blue shift, lower reverse leakage current and decreases efficiency droop compared with the MPLEDs. These results suggest the feasibility of using NPSi for the growth of high quality and power LEDs on Si substrates.
Optical and Electrical Properties of GaN-Based Light Emitting Diodes Grown on Micro- and Nano-Scale Patterned Si Substrate
(2011-07-01)
Chiu, Ching-Hsueh
;
Lin, Chien-Chung
;
Deng, Dong-Mei
;
Lin, Da-Wei
;
Li, Jin-Chai
We investigate the optical and electrical characteristics of the GaN-based light emitting diodes (LEDs) grown on micro-and nano-scale patterned silicon substrate (MPLEDs and NPLEDs). The transmission electron microscopy images reveal the suppression of threading dislocation density in InGaN/GaN structure on nano-pattern substrate due to nano-scale epitaxial lateral overgrowth. The plan-view and cross-section cathodo luminescence mappings show less defective and more homogeneous active quantum-well region growth on nano-porous substrates. From temperature-dependent photoluminescence (PL) and low temperature time-resolved PL measurement, NPLEDs have better carrier confinement and higher radiative recombination rate than MPLEDs. In terms of device performance, NPLEDs exhibit smaller electroluminescence peak wavelength blue shift, lower reverse leakage current and decrease in efficiency droop when compared with the MPLEDs. These results suggest the feasibility of using NPSi for the growth of high quality and power LEDs on Si substrates.
Optical cross-talk reduction in a quantum-dot-based full-color micro-light-emitting-diode display by a lithographic-fabricated photoresist mold
(2017-10-01)
Lin, Huang-Yu
;
Sher, Chin-Wei
;
Hsieh, Dan-Hua
;
Chen, Xin-Yin
;
Chen, Huang-Ming Philip
In this study, a full-color emission red-green-blue (RGB) quantum-dot (QD)-based micro-light-emitting-diode (micro-LED) array with the reduced optical cross-talk effect by a photoresist mold has been demonstrated. The UV micro-LED array is used as an efficient excitation source for the QDs. The aerosol jet technique provides a narrow linewidth on the micrometer scale for a precise jet of QDs on the micro-LEDs. To reduce the optical cross-talk effect, a simple lithography method and photoresist are used to fabricate the mold, which consists of a window for QD jetting and a blocking wall for cross-talk reduction. The cross-talk effect of the well-confined QDs in the window is confirmed by a fluorescence microscope, which shows clear separation between QD pixels. A distributed Bragg reflector is covered on the micro-LED array and the QDs' jetted mold to further increase the reuse of UV light. The enhanced light emission of the QDs is 5%, 32%, and 23% for blue, green, and red QDs, respectively. (C) 2017 Chinese Laser Press
Resonant-enhanced full-color emission of quantum-dot-based micro LED display technology
(2015-12-14)
Han, Hau-Vei
;
Lin, Huang-Yu
;
Lin, Chien-Chung
;
Chong, Wing-Cheung
;
Li, Jie-Ru
Colloidal quantum dots which can emit red, green, and blue colors are incorporated with a micro-LED array to demonstrate a feasible choice for future display technology. The pitch of the micro-LED array is 40 mu m, which is sufficient for high-resolution screen applications. The method that was used to spray the quantum dots in such tight space is called Aerosol Jet technology which uses atomizer and gas flow control to obtain uniform and controlled narrow spots. The ultra-violet LEDs are used in the array to excite the red, green and blue quantum dots on the top surface. To increase the utilization of the UV photons, a layer of distributed Bragg reflector was laid down on the device to reflect most of the leaked UV photons back to the quantum dot layers. With this mechanism, the enhanced luminous flux is 194% (blue), 173% (green) and 183% (red) more than that of the samples without the reflector. The luminous efficacy of radiation (LER) was measured under various currents and a value of 165 lm/Watt was recorded. (C)2015 Optical Society of America