Improvement of electroluminescence characteristicsof poroussilicon LED by using amorphous silicon layers

Chen, Yen-Ann; Liang, Nai-Yuan; Laih, Li-Hong; Tsay, Wen-Chin; Chang, Min-Kuan; Hong, Jyh-Wong

doi:10.1049/el:19970994

Cited by 6 publications

(2 citation statements)

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“…Instead of light reflecting at grating surfaces, the light scatters at these surfaces for partial transmission of otherwise completely reflected light. A variety of methods exist to construct these gratings, including wet etching with an amorphous sacrificial layer [6][7][8][9] or laser etching to obtain a more periodic spacing [10][11][12][13][14]. Any of these methods can etch a transmission grating on a semiconductor surface, each with their respective advantages and disadvantages.…”

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Top transmission grating GaN LED simulations for light extraction improvement

et al. 2011

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We study the top transmission grating's improvement on GaN LED light extraction efficiency. We use the finite difference time domain (FDTD) method, a computational electromagnetic solution to Maxwell's equations, to measure light extraction efficiency improvements of the various grating structures. Also, since FDTD can freely define materials for any layer or shape, we choose three particular materials to represent our transmission grating: 1) nonlossy p-GaN, 2) lossy indium tin oxide (ITO), and 3) non-lossy ITO (�=0). We define a regular spacing between unit cells in a crystal lattice arrangement by employing the following three parameters: grating cell period (�), grating cell height (d), and grating cell width (w). The conical grating model and the cylindrical grating model are studied. We also presented in the paper directly comparison with reflection grating results. Both studies show that the top grating has better performance, improving light extraction efficiency by 165%, compared to that of the bottom reflection grating (112%), and top-bottom grating (42%). We also find that when grating cells closely pack together, a transmission grating maximizes light extraction efficiency. This points our research towards a more closely packed structure, such as a 3-fold symmetric photonic crystal structure with triangular symmetry and also smaller feature sizes in the nano-scale, such as the wavelength of light at 460 nm, half-wavelengths, quarter wavelengths, etc.

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Top transmission grating GaN LED simulations for light extraction improvement

et al. 2011

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“…To further mitigate the problems of total internal reflection, the emission surface can be patterned to form a transmission grating that offers the trapped light more angles of escape. This can be done with a variety of methods including wet etching with an amorphous sacrificial layer [6]- [9] or by laser etching to obtain a more periodic spacing [10]- [14]. In addition, it has been shown that the same patterning can also apply to a Ag reflector plate in either pillar or hole grating shapes to form a reflection grating [15], [16].…”

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Study of Top and Bottom Photonic Gratings on GaN LED With Error Grating Models

Trieu

Jin

2010

IEEE J. Quantum Electron.

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The gallium nitride (GaN) light-emitting-diode (LED) top-bottom (or transmission-reflection) grating simulation results with error grating model are presented. The microstruc ture GaN bottom hole and top pillar gratings are calculated and compared with the non-grating (flat) case. Grating shapes simu lated are either conical or cylindrical. A direct comparison of 181 different combined transmission-reflection grating cases using the finite difference time domain method is presented. The simulation results show that simple or direct combinations of the optimized top grating with the optimized bottom grating only produce a 42% light extraction improvement compared to the non-grating case, which is much lower than that of an optimized single grating case. This is due to the mismatch of grating parameters with the direct addition of the second grating structure, which changes the optical field distribution in the LEDs. Therefore, it is very im portant to optimize both top and bottom gratings simultaneously for the double-grating design. We also show the optimization of a double grating structure can achieve better performance than a single grating. Finally, transmission-reflection error gratings are also presented. It is also the first time to present randomization in GaN LED grating design and its effects in fabrication. Our data shows that the favorable light extraction improvement is at approximately 10-15% randomization. The randomization can achieve 230% improvement over the original grating at a randomization intensity factor of 12.8%.

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Nanocrystalline Si EL Devices

Gelloz

Koshida

2009

Nanostructure Science and Technology

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Improvement of electroluminescence characteristicsof poroussilicon LED by using amorphous silicon layers

Cited by 6 publications

References 6 publications

Top transmission grating GaN LED simulations for light extraction improvement

Top transmission grating GaN LED simulations for light extraction improvement

Study of Top and Bottom Photonic Gratings on GaN LED With Error Grating Models

Nanocrystalline Si EL Devices

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