Highly Efficient and Bright LEDs Overgrown on GaN Nanopillar Substrates

Abstract-In this paper, a high quality ultraviolet lightemitting diodes (UV-LEDs) at 375 nm was developed using a heavy Si-doping technique with metal organic chemical vapor deposition. By using high-resolution X-ray diffraction, the full width at half-maximum of the rocking curve shows that the GaN film inserting a heavily Si-doped GaN layer (Si-HDL) had high crystalline quality. From the transmission electron microscopy image, the threading dislocation density was decreased after inserting a Si-HDL between undoped and n-doped GaN layers by nanoscale epitaxial lateral overgrowth. As a result, a much smaller reverse current and a higher light output were achieved. The improvement of light output at an injection current of 20 mA was enhanced by 40%. Therefore, we can use an in-situ nano pattern without complex photolithography and etching process and improve the internal quantum efficiency of UV-LEDs.Index Terms-Internal quantum efficiency, metal-organic chemical vapor deposition, nanoscale epitaxial lateral overgrowth, ultraviolet light emitting diodes.

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“…5. This nano-scaled patterned substrate has been proved to be beneficial towards TDDs reduction, like shown in the past [25]- [26].…”

Section: Resultsmentioning

confidence: 79%

Improved Output Power of InGaN-Based Ultraviolet LEDs Using a Heavily Si-Doped GaN Insertion Layer Technique

Chiu

Lin

et al. 2012

IEEE J. Quantum Electron.

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“…The bottom-up growth of GaN nanopillars has been achieved by a number of groups using molecular beam epitaxy (MBE). 10,15,[27][28][29][30][31][32] This growth mechanism does not necessarily require a catalyst or nanoscale masks, but only the right growth conditions, namely the III/V ratio, the gas fl ows and the growth temperature. Moreover, it is noticeable that the nanopillar diameter, density and distribution can be controlled by the growth conditions.…”

Section: Bottom-up Methodsmentioning

confidence: 99%

“…A molecular beam epitaxy (MBE) technique will be discussed in this context, for which a 71% increase of output power has been demonstrated. 15 …”

Section: Introductionmentioning

confidence: 99%

Nanostructured LEDs

Lin

Chiu

et al. 2014

Nitride Semiconductor Light-Emitting Diodes (LEDs)

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“…In the past decade, there have been many studies focused on enhancing the characteristic of the GaN-based blue chip including the internal quantum efficiency [7], efficiency droop [8] and light extraction [9,10]. Furthermore, the air voids/SiO 2 nanomasks and nanopillar substrates are employed to improve the crystalline quality of the GaN-based epilayer and increase the output efficiency [11,12]. Other than the performance of the blue chip, external package can also play an important part in terms of lumen enhancement.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

et al. 2014

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This study demonstrates the hybrid structure with high lumen efficiency and uniform angular-dependent correlated color temperature (CCT) for warm white LED. Compared to the conventional structures, the hybrid structure combines the advantage of the two different fabrication methods including dispense and pulse spray method together, which can produce the high quality lighting source. The experimental results indicate that the hybrid structure yielded higher lumen efficiency than conventional phosphor structure because of the gradual refractive index difference from the coating layer to the dispense layer. Moreover, the CCT deviations of the hybrid phosphor structure could be reduced to 65 K in range of −70 to 70 degrees. This is attributed to the uniform color mixing of the blue, yellow and red band in the hybrid phosphor structure. In addition, the chromaticity coordinate shift compared to the hybrid structure with the dispense structure are almost the same at a current regulation from 20 mA to 500 mA. We believe that the technology of the hybrid structure with high lumen efficiency and uniform angular-dependent CCT is suitable for in the general lighting application.

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Highly Efficient and Bright LEDs Overgrown on GaN Nanopillar Substrates

Abstract: Abstract-We presented a study of high-performance GaNbased light emitting diodes (LEDs) using a GaN nanopillars (NPs) structure grown on sapphire substrate by integrating RF-plasma molecular beam epitaxy (

Cited by 21 publications

References 33 publications

Improved Output Power of InGaN-Based Ultraviolet LEDs Using a Heavily Si-Doped GaN Insertion Layer Technique

Improved Output Power of InGaN-Based Ultraviolet LEDs Using a Heavily Si-Doped GaN Insertion Layer Technique

Nanostructured LEDs

Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

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