Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening

Fujii, Tetsuo; Gao, Yan; Sharma, Rajat; Hu, Evelyn L.; DenBaars, Steven P.; Nakamura, Shuji

doi:10.1063/1.1645992

Cited by 1,299 publications

(703 citation statements)

References 12 publications

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“…Conventional GaN-based light-emitting diodes ͑LEDs͒ still suffer from limited light extraction, due to total internal refraction ͑TIR͒ of the emitted light at the interface between semiconductor and air. Efficient solutions, such as flip-chip 1 or surface-roughened 2 LEDs, unfortunately require complex fabrication procedures. On the other hand, photonic crystal ͑PhC͒ were studied extensively in a variety of materials in the last decade, as an efficient means to enhance light extraction in LEDs, while keeping a full planar device fabrication.…”

mentioning

confidence: 99%

Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution

David

Fujii

Sharma

et al. 2006

Applied Physics Letters

204

156

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International audienceWe relate the currently limited efficiency of photonic crystal (PhC)--assisted gallium nitride light-emitting diodes (LEDs) to the existence of unextracted guided modes. To remedy this, we introduce epitaxial structures which modify the distribution of guided modes. LEDs are fabricated according to this concept, and the tailored band structure is determined experimentally. We investigate theoretically the consequences of this improvement, which significantly enhances the potential for efficient light extraction by PhCs

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mentioning

confidence: 99%

Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution

David

Fujii

Sharma

et al. 2006

Applied Physics Letters

204

156

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“…16 The observation of the atomically smooth (1 1 22 ) chemically etched surface may provide an important regrown surface on the etched high quality GaN in LEO a-plane GaN wing region, which is observed as the stacking fault free materials. 12 All these studies are currently under exploration.…”

mentioning

confidence: 99%

Dislocation- and crystallographic-dependent photoelectrochemical wet etching of gallium nitride

Gao

Craven

Speck

et al. 2004

Applied Physics Letters

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Polarity and dislocation dependence study of photoelectrochemical wet etching on GaN was carried out on lateral epitaxial overgrown nonpolar (112̄0)a-GaN/(11̄02)r-plane sapphire substrate. This LEO nonpolar GaN sample has low dislocation density Ga- and N-faces exposed horizontally in opposite directions, which can be exposed to identical etching conditions for both polarity and dislocation dependence study. It is observed that N-face GaN is essentially much chemically active than Ga-face GaN, which shows the hexagonal pyramids with {101̄1̄} facets on the etched N face. No obvious etching was observed on Ga face in the same etch condition. As for dislocation dependence, the “wing” (low dislocation density) region was etched faster than the “window” (high dislocation density) region. Smooth etched surfaces were formed with the (1̄1̄22̄) facet as an etch stop plane both on Ga and N-wing region.

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“…8 Among these, surface roughening is the most economical and feasible for integration into an LED production line. [9][10][11] To the best of our knowledge, an effective method for fabricating roughened p-GaN is still not available. Although a variety of technologies have been used in attempts to create roughened p-GaN, their effects seem to be limited.…”

confidence: 99%

“…Email: liuduo@sdu.edu.cn It should be emphasized that although electroless photochemical etching has been utilized on n-GaN, 9 it cannot be directly applied to p-GaN because of band bending induced by the dopant and large spontaneous polarization of GaN, such that photogenerated holes can barely participate in the etching reactions. 15,16 In this letter, we report a method of metal-assisted electroless photochemical etching to fabricate nanoporous p-GaN.…”

confidence: 99%

Metal-assisted electroless fabrication of nanoporous p-GaN for increasing the light extraction efficiency of light emitting diodes

et al. 2012

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We report metal-assisted electroless fabrication of nanoporous p-GaN to improve the light extraction efficiency of GaN-based light emitting diodes (LEDs). Although it has long been believed that p-GaN cannot be etched at room temperature, in this study we find that Ag nanocrystals (NCs) on the p-GaN surface enable effective etching of p-GaN in a mixture of HF and K2S2O8 under ultraviolet (UV) irradiation. It is further shown that the roughened GaN/air interface enables strong scattering of photons emitted from the multiple quantum wells (MQWs). The light output power measurements indicate that the nanoporous LEDs obtained after 10 min etching show a 32.7% enhancement in light-output relative to the conventional LEDs at an injection current of 20 mA without significant increase of the operating voltage. In contrast, the samples etched for 20 min show performance degradation when compared with those etched for 10 min, this is attributed to the current crowding effect and increased surface recombination rate

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Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening

Cited by 1,299 publications

References 12 publications

Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution

Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution

Dislocation- and crystallographic-dependent photoelectrochemical wet etching of gallium nitride

Metal-assisted electroless fabrication of nanoporous p-GaN for increasing the light extraction efficiency of light emitting diodes

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