Browsing by Author "Yin, Yu-Feng"

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Mechanisms of the Asymmetric Light Output Enhancements in a-Plane GaN Light-Emitting Diodes With Photonic Crystals
(2014-12-01)
Li, Hsiang-Wei
;
Yin, Yu-Feng
;
Chang, Chen-Yu
;
Tsai, Chen-Hung
;
Hsu, Yen-Hsiang
The unique properties of nonpolar GaN light-emitting diodes (LEDs) have the advantages of generating polarized light emission. The employment of asymmetric 2-D photonic crystals (PhCs) can further enhance the light polarization ratio. In addition, it was generally recognized that the Purcell effect can increase the internal quantum efficiency of the LEDs with PhCs. In this paper, we study the properties of optical modes from different crystal planes. The Purcell effect is analyzed based on the PhCs and material crystal orientations. With different transition probability of the polarized photons in valence bands, the corresponding Purcell effect enhancement on the quantum efficiency varies.
Polarization ratio enhancement of a-plane GaN light emitting diodes by asymmetric two-dimensional photonic crystals
(2014-05-21)
Chou, Yen
;
Li, Hsiang-Wei
;
Yin, Yu-Feng
;
Wang, Yu-Ting
;
Lin, Yen-Chen
Fabricating photonic crystals (PhCs) on GaN based non-polar light emitting diodes (LEDs) is an effective way to increase light extraction and meanwhile to preserve or improve polarization ratio. In this work, a-plane GaN LEDs with two-dimensional PhCs were demonstrated. With the E // m polarized modes (which mean the optical polarization with the electric field parallel to m-axis) as the target of diffraction, we matched E//m modes to the photonic bands and aligned E//c modes to fall within the photonic band gap. The results show stronger E//m but weaker E//c mode diffractions on both c- and m-axes. At the vertical direction, the polarization ratio is enhanced from 45.8% for the planar device to 52.3% for the LEDs with PhCs. (C) 2014 AIP Publishing LLC.