Browsing by Author "Han, Jung"

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Effect of Controlled Growth Dynamics on the Microstructure of Nonpolar a-Plane GaN Revealed by X-ray Diffraction
(2009-07-01)
Sun, Qian
;
Ko, Tsung-Shine
;
Yerino, Christopher D.
;
Zhang, Yu
;
Lee, In-Hwan
This paper reports the effect of controlled growth dynamics, as monitored by in situ optical reflectance, on the microstructure of nonpolar a-plane GaN films grown on r-plane sapphire. The mosaic microstructure of a-plane GaN and its anisotropy are evaluated by X-ray rocking curve (XRC) measurements. By inserting a pronounced islanding stage followed by an enhanced lateral growth, pit-free a-plane GaN has been achieved showing an XRC linewidth of similar to 0.18 and similar to 0.3 degrees for on- and off-axes planes, respectively, with only minor anisotropy. The density of basal-plane stacking faults is reduced by similar to 70% as determined by a modified Williamson-Hall X-ray analysis. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/JJAP.48.071002
Full-color micro-LED display with high color stability using semipolar (20-21) InGaN LEDs and quantum-dot photoresist
(2020-05-01)
Chen, Sung-Wen Huang
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Huang, Yu-Ming
;
Singh, Konthoujam James
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Hsu, Yu-Chien
;
Liou, Fang-Jyun
Red-green-blue (RGB) full-color micro light-emitting diodes (mu-LEDs) fabricated from semipolar (20-21) wafers, with a quantum-dot photoresist color-conversion layer, were demonstrated. The semipolar (20-21) InGaN/GaN mu-LEDs were fabricated on large (4 in.) patterned sapphire substrates by orientation-controlled epitaxy. The semipolar mu-LEDs showed a 3.2 nm peak wavelength shift and a 14.7% efficiency droop under 200 A/cm(2 )injected current density, indicating significant amelioration of the quantum-confined Stark effect. Because of the semipolar mu-LEDs' emission-wavelength stability, the RGB pixel showed little color shift with current density and achieved a wide color gamut (114.4% NTSC space and 85.4% Rec. 2020). (C) 2020 Chinese Laser Press
High-Bandwidth Green Semipolar (20-21) InGaN/GaN Micro Light-Emitting Diodes for Visible Light Communication
(2020-08-19)
Chen, Sung-Wen Huang
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Huang, Yu-Ming
;
Chang, Yun-Han
;
Lin, Yue
;
Liou, Fang-Jyun
The light-emitting diode (LED) is among promising candidates of light sources in visible light communication (VLC); however, strong internal polarization fields in common c-plane LEDs, especially green LEDs, result in low frequency and limited transmission performance. This study aims to overcome the limited 3-dB bandwidth of long-wavelength InGaN/GaN LEDs. Thus, semipolar (20-21) micro-LEDs (mu LEDs) were fabricated through several improved approaches on epitaxy and chip processes. The mu LED exhibits a 525 nm peak wavelength and good polarization performance. The highest 3-dB bandwidth up to 756 MHz and 1.5 Gbit/s data rate was achieved under a current density of 2.0 kA/cm(2). These results suggest a good transmission capacity of green semipolar (20-21) mu LEDs in VLC applications.
Low Efficiency Droop Green Nano-Pyramid {10(1)over-bar1} InGaN/GaN Multiple Quantum Well LED
(2014)
Chang, Shih-Pang
;
Xiong, Kang-lin
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Lin, Da-Wei
;
Cheng, Yuh-Jen
;
Han, Jung
We report a low efficiency droop 520 nm green nano-pyramid InGaN/GaN multiple quantum well (MQW) LED. MQWs were grown on the semipolar {10 (1) over bar1} nano-pyramid facets. The device physics will be discussed in details.
Mesoporous GaN for Photonic Engineering-Highly Reflective GaN Mirrors as an Example
(2015-07-01)
Zhang, Cheng
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Park, Sung Hyun
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Chen, Danti
;
Lin, Da-Wei
;
Xiong, Wen
A porous medium is a special type of material where voids are created in a solid medium. The introduction of pores into a bulk solid can profoundly affect its physical properties and enable interesting mechanisms. In this paper, we report the use of mesoporous GaN to address a long-standing challenge in GaN devices: tuning the optical index in epitaxial structures without compromising the structural and electrical properties. By controlling the doping and electrochemical etching bias, we are able to control the pore morphology from macro- to meso- and microporous. The meso- and microporous GaN can be considered a new form of GaN with unprecedented optical index tunability. We examine the scattering loss in a porous medium quantitatively using numerical, semiempirical, and experimental methods. It is established that the optical loss due to scattering is well within the acceptable range. While being perfectly lattice-matched to GaN, the porous GaN layers are found to be electrically highly conductive. As an example of optical engineering, we demonstrate record high reflectances (R > 99.5%) from epitaxial mesoporous GaN mirrors that can be controllably fabricated, a result that is bound to impact GaN opto and photonic technologies.
Self-assembled InN growth on GaN nanorod
(2014)
Chang, Shih-Pang
;
Lai, Yung-Yu
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Cheng, Yuh-Jen
;
Han, Jung
;
Kuo, Hao-Chung
We report a self-assembled InN epitaxial growth on GaN nanorods. Crystalline InN hexagonal structure was selectively grown on the sidewall edges of GaN hexagonal nanorods. The growth mechanism and the photoluminescent property will be discussed.
Significantly Improved Luminescence Properties of Nitrogen-Polar (000(1over bar>)over-bar) InGaN Multiple Quantum Wells Grown by Pulsed Metalorganic Chemical Vapor Deposition
(2015-01-14)
Song, Jie
;
Chang, Shih-Pang
;
Zhang, Cheng
;
Hsu, Ta-Cheng
;
Han, Jung
We have demonstrated nitrogen-polar (000 (1) over bar) (N-polar) InGaN multiple quantum wells (MQWs) with significantly improved luminescence properties prepared by pulsed metalorganic chemical vapor deposition. During the growth of InGaN quantum wells, Ga and N sources are alternately injected into the reactor to alter the surface stoichiometry. The influence of flow duration in pulsed growth mode on the luminescence properties has been studied. We find that use of pulsed-mode creates a high density of hexagonal mounds with an increased InGaN growth rate and enhanced In composition around screw-type dislocations, resulting in remarkably improved luminescence properties. The mechanism of enhanced luminescence caused by the hexagonal mounds is discussed. Luminescence properties of N-polar InGaN MQWs grown with short pulse durations have been significantly improved in comparison with a sample grown by a conventional continuous growth method.