Green InGaN/GaN based LEDs: high luminance and blue shift

Daami, Anis; Ochsenbein, F.; Dupré, Ludovic; Licitra, C.; Henry, Franck; Templier, F.; Calvez, S.

doi:10.1117/12.2509396

Cited by 10 publications

(8 citation statements)

References 15 publications

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“…Figure d and e show the EL emission images as a function of injection current for both the μLEDs with DBR and the μLEDs without DBR, respectively, demonstrating that the light that the μLEDs without DBR emit evolves initially from yellow at 5 mA, through yellow/greenish at 10 mA, then pure green at 20 mA, and finally to green/blueish at 60 mA. Such a blue-shift in emission wavelength with increasing injection current is the fingerprint of QCSE. − Such μLEDs cannot be used for the fabrication of a microdisplay. In contrast, the μLEDs with DBR constantly emit green light throughout all the injection current.…”

Section: Results and Discussionmentioning

confidence: 99%

Simple Approach to Mitigate the Emission Wavelength Instability of III-Nitride μLED Arrays

Arriba

Feng

et al. 2022

ACS Photonics

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III-nitride semiconductors and their heterojunctions exhibit intrinsic polarization due to the asymmetry of their wurtzite structure, which determines all the fundamental properties of III-nitride optoelectronics. The intrinsic polarization-induced quantum-confined Stark effect leads to an emission wavelength shift with increasing injection current for III-nitride visible LEDs, forming an insurmountable barrier for the fabrication of a full color display. For instance, a yellow LED designed to produce yellow light emits green or blue light at an elevated current, while a green (blue) LED gives off blue (violet) light with increasing current. This color instability becomes a serious issue for a microdisplay such as the displays for augmented reality (AR)/virtual reality (VR) typically utilized at proximity to the eye, where human eyes are sensitive to a tiny change in light color. It is well-known that an optical mode wavelength for a microcavity is insensitive to injection current. In this work, we have demonstrated an approach to epitaxially integrating microLEDs (green microLEDs as an example, one of the key components for a full color microdisplay) and a microcavity. This allows the emission from the microLEDs to be coupled with the microcavity, leading to a negligible emission wavelength shift with increasing injection current. In contrast, identical microLEDs but without a microcavity show a large emission wavelength shift from 560 nm down to 510 nm, measured under identical conditions. This approach provides a simple solution to resolving the 30-year issue in the field of III-nitride optoelectronics.

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Section: Results and Discussionmentioning

confidence: 99%

Simple Approach to Mitigate the Emission Wavelength Instability of III-Nitride μLED Arrays

Arriba

Feng

et al. 2022

ACS Photonics

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“…Characterization of our µLED devices are shown in Figure 1e-g. The spectral peak is at 545 nm and the full width half max is 20 nm, and exhibit the expected slight blue-shifting at higher current densities typical of green GaN 63 (Figure 1e). Our devices were able to generate significant light output below 3V, enabling the use of low-voltage electronics (Figure 1f).…”

Section: Resultsmentioning

confidence: 86%

A thin-film optogenetic visual prosthesis

Knudsen

Zappitelli

Brown

et al. 2023

Preprint

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Retinitis pigmentosa and macular degeneration lead to photoreceptor death and loss of visual perception. Despite recent progress, restorative technologies for photoreceptor degeneration remain largely unavailable. Here, we describe a novel optogenetic visual prosthesis (FlexLED) based on a combination of a thin-film retinal display and optogenetic activation of retinal ganglion cells (RGCs). The FlexLED implant is a 30 um thin, flexible, wireless uLED display with 8,192 pixels, each with an emission area of 66 um2. The display is affixed to the retinal surface, and the electronics package is mounted under the conjunctiva in the form factor of a conventional glaucoma drainage implant. In a rabbit model of photoreceptor degeneration, optical stimulation of the retina using the FlexLED elicits activity in visual cortex. This technology is readily scalable to hundreds of thousands of pixels, providing a route towards an implantable optogenetic visual prosthesis capable of generating vision by stimulating RGCs at near-cellular resolution.

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“…According to the experiment results, Epi A shows a stronger peak of 365 nm in UV region, which is owing to the current path flowing through the 2DEG channel. At high current level, a blue shift can be found in Epi A, which is attributed to the Quantum Confined Stark Effect (QCSE) [ 10 ]. Different from Epi A, Epi B shows a major peak at 525 nm, which indicates better radiative recombination in the InGaN quantum well due to much-improved electron confinement and transportation in the well.…”

Section: Resultsmentioning

confidence: 99%

Study on the Effects of Quantum Well Location on Optical Characteristics of AlGaN/GaN Light-Emitting HEMT

et al. 2023

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In this study, AlGaN/GaN light-emitting HEMTs (LE-HEMT) with a single quantum well inserted in different locations in the epitaxy layers are fabricated and analyzed. For both structures, light-emitting originated from electrons in the 2DEG and holes from the p-GaN for radiative recombination is located in the quantum well. To investigate the importance of the location of single quantum well, optical characteristics are compared by simulation and experimental results. The experimental results show that the main light-emitting wavelength is shifted from 365 nm in the UV range to 525 nm in the visible range when the radiative recombination is confined in the quantum well and dominates among other mechanisms. Epi B, which has a quantum well above the AlGaN barrier layer in contrast to Epi A which has a quantum well underneath the barrier, shows better intensity and uniformity in light-emitting. According to the simulation results showing the radiative distribution and electron concentrations for both structures, the lower quantum efficiency is due to the diverse current paths in Epi A. On the other hand, Epi B shows better quantum confinement and therefore better luminescence in the same bias condition, which is consistent with experimental observations. These findings are critical for advancing the performance of LE-HEMTs.

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Green InGaN/GaN based LEDs: high luminance and blue shift

Cited by 10 publications

References 15 publications

Simple Approach to Mitigate the Emission Wavelength Instability of III-Nitride μLED Arrays

Simple Approach to Mitigate the Emission Wavelength Instability of III-Nitride μLED Arrays

A thin-film optogenetic visual prosthesis

Study on the Effects of Quantum Well Location on Optical Characteristics of AlGaN/GaN Light-Emitting HEMT

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