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Optoelectronic Simulations of InGaN-Based Green Micro-Resonant Cavity Light-Emitting Diodes with Staggered Multiple Quantum Wells

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Crystals 2023, 13(4), 572; https://doi.org/10.3390/cryst13040572 - 27 Mar 2023

Viewed by 806

Abstract

In this research, we compared the performance of commercial μ-LEDs and three-layered staggered QW μ-LED arrays. We also investigated the self-heating effect. We proposed a green micro-resonant cavity light-emitting diode (µ-RCLED) that consists of a three-layer staggered InGaN with multiple quantum wells (MQWs), [...] Read more.

In this research, we compared the performance of commercial μ-LEDs and three-layered staggered QW μ-LED arrays. We also investigated the self-heating effect. We proposed a green micro-resonant cavity light-emitting diode (µ-RCLED) that consists of a three-layer staggered InGaN with multiple quantum wells (MQWs), a bottom layer of nanoporous n-GaN distributed Bragg reflectors (DBRs), and a top layer of Ta₂O₅/SiO₂ DBRs. We systematically performed simulations of the proposed µ-RCLEDs. For the InGaN MQWs with an input current of 300 mA, the calculated wavefunction overlaps are 8.8% and 18.1% for the regular and staggered structures, respectively. Furthermore, the staggered MQWs can reduce the blue-shift of electroluminescence from 10.25 nm, obtained with regular MQWs, to 2.25 nm. Due to less blue-shift, the output power can be maintained even at a high input current. Conversely, by employing 6.5 pairs of Ta₂O₅/SiO₂ DBRs stacks, the full width at half maximum (FWHM) can be significantly reduced from 40 nm, obtained with ordinary µ-LEDs, to 0.3 nm, and a divergence angle smaller than 60° can be obtained. Our simulation results suggest that the µ-RCLEDs can effectively resolve the wavelength instability and color purity issues of conventional µ-LEDs. Full article

(This article belongs to the Special Issue III-Nitride-Based Light-Emitting Devices)

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Open AccessArticle

Epitaxial Lateral Overgrowth of {11-22} InGaN Layers Using Patterned InGaN Template and Improvement of Optical Properties from Multiple Quantum Wells

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Narihito Okada

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Kazuyuki Tadatomo

Crystals 2022, 12(10), 1373; https://doi.org/10.3390/cryst12101373 - 27 Sep 2022

Viewed by 791

Abstract

We report the growth and characterization of thick, completely relaxed {11-22}-oriented InGaN layers using epitaxial lateral overgrowth (ELO). Although it was difficult to grow ELO-InGaN layers on patterned GaN templates, we succeeded in growing ELO-InGaN layers on a patterned InGaN template. The full [...] Read more.

We report the growth and characterization of thick, completely relaxed {11-22}-oriented InGaN layers using epitaxial lateral overgrowth (ELO). Although it was difficult to grow ELO-InGaN layers on patterned GaN templates, we succeeded in growing ELO-InGaN layers on a patterned InGaN template. The full width at half maximum of the X-ray rocking curve of ELO-InGaN on the InGaN templates was less than that of non-ELO InGaN. The photoluminescence intensity of InGaN/GaN multiple quantum wells on ELO-InGaN was approximately five times stronger than that on the {11-22} GaN template. Full article

(This article belongs to the Special Issue III-Nitride-Based Light-Emitting Devices)

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Open AccessArticle

Study of High Polarized Nanostructure Light-Emitting Diode

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Crystals 2022, 12(4), 532; https://doi.org/10.3390/cryst12040532 - 11 Apr 2022

Cited by 1 | Viewed by 1402

Abstract

In this study, we investigated the characteristic difference between the two different configurations of the three-dimensional shell–core nanorod LED. We achieve a degree of polarization of 0.545 for tip-free core–shell nanorod LED and 0.188 for tip core–shell nanorod LED by combining the three-dimensional [...] Read more.

In this study, we investigated the characteristic difference between the two different configurations of the three-dimensional shell–core nanorod LED. We achieve a degree of polarization of 0.545 for tip-free core–shell nanorod LED and 0.188 for tip core–shell nanorod LED by combining the three-dimensional (3D) structure LED with photonic crystal. The ability of low symmetric modes generated by photonic crystals to enhance degree of polarization has been demonstrated through simulations of photonic crystals. In addition, light confinement in GaN-based nanorod structures is induced by total internal reflection at the GaN/air interface. The combination of 3D core–shell nanorod LED and photonic crystals cannot only produce a light source with a high degree of polarization, but also a narrow divergence angle up to 56°. These 3D LEDs may pave the way for future novel optoelectronic components. Full article

(This article belongs to the Special Issue III-Nitride-Based Light-Emitting Devices)

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Open AccessArticle

Improving Mini-LED Pattern Quality by Using Distributed Bragg Reflector and Digital Twin Technology

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Shu-Hsiu Chang

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Che-Hsuan Huang

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Chatherine Langpoklakpam

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Konthoujam James Singh

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Chien-Chung Lin

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Hao-Chung Kuo

Crystals 2022, 12(4), 529; https://doi.org/10.3390/cryst12040529 - 10 Apr 2022

Viewed by 1216

Abstract

Fine-pitch backlight technology is rapidly evolving along with display technology, and chips are increasingly designed for direct integration with modules. This study used a distributed Bragg reflector (DBR) for mini light-emitting diode (mini-LED) backlights with high dynamic contrast and developed a digital twin [...] Read more.

Fine-pitch backlight technology is rapidly evolving along with display technology, and chips are increasingly designed for direct integration with modules. This study used a distributed Bragg reflector (DBR) for mini light-emitting diode (mini-LED) backlights with high dynamic contrast and developed a digital twin design by using a light-emitting diode (LED) and a distributed Bragg reflector (DBR). Full article

(This article belongs to the Special Issue III-Nitride-Based Light-Emitting Devices)

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Open AccessArticle

Pulsed Sputtering Preparation of InGaN Multi-Color Cascaded LED Stacks for Large-Area Monolithic Integration of RGB LED Pixels

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Crystals 2022, 12(4), 499; https://doi.org/10.3390/cryst12040499 - 04 Apr 2022

Cited by 2 | Viewed by 1512

Abstract

Micro-LEDs have been attracting attention as a potential candidate for the next generation of display technology. Here we demonstrate the feasibility of large-area monolithic integration of multi-color InGaN micro-LEDs via pulsed sputtering deposition (PSD) and a standard photolithographical technique. The PSD allows for [...] Read more.

Micro-LEDs have been attracting attention as a potential candidate for the next generation of display technology. Here we demonstrate the feasibility of large-area monolithic integration of multi-color InGaN micro-LEDs via pulsed sputtering deposition (PSD) and a standard photolithographical technique. The PSD allows for sequential epitaxial growth of blue and green InGaN LED stacks connected with the GaN based tunneling junction. The tunneling junctions serve as protective layers on p-type GaN against the dry etching damage and hole injection layers in each blue and green emission InGaN active layer. The tunneling junction-connected multi-color InGaN LED stack contributes to the high-density and large-area monolithic integration of RGB micro-LEDs using standard photolithography and the ICP-dry etching method. Full article

(This article belongs to the Special Issue III-Nitride-Based Light-Emitting Devices)

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Open AccessArticle

Investigation on Light Extraction Behavior of Surface Plasmon-Coupled Deep-Ultraviolet LED in Different Emission Directions

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Crystals 2022, 12(1), 82; https://doi.org/10.3390/cryst12010082 - 07 Jan 2022

Cited by 2 | Viewed by 831

Abstract

The light extraction behavior of an AlGaN-based deep-ultraviolet LED covered with Al nanoparticles (NPs) is investigated by three-dimensional finite-difference time-domain simulation. For the transmission spectra of s- and p-polarizations in different emission directions, the position of maximum transmittance can be changed from (θ [...] Read more.

The light extraction behavior of an AlGaN-based deep-ultraviolet LED covered with Al nanoparticles (NPs) is investigated by three-dimensional finite-difference time-domain simulation. For the transmission spectra of s- and p-polarizations in different emission directions, the position of maximum transmittance can be changed from (θ = 0°, λ = 273 nm) to (θ = 0°, λ = 286 nm) by increasing the diameter of Al NPs from 40 nm to 80 nm. In the direction that is greater than the critical angle, the transmittance of s-polarization is very small due to the strong absorption of Al NPs, while the transmittance spectrum of p-polarization can be observed obviously for the 80 nm Al NPs structure. For a ~284 nm AlGaN-based LED with surface plasmon (SP) coupling, although the luminous efficiency is significantly improved due to the improvement of the radiation recombination rate as compared with the conventional LED, the light extraction efficiency (LEE) is lower than 2.61% of the conventional LED without considering the lateral surface extraction and bottom reflection. The LEE is not greater than ~0.98% (~2.12%) for an SP coupling LED with 40 nm (80 nm) Al NPs. The lower LEE can be attributed to the strong absorption of Al NPs. Full article

(This article belongs to the Special Issue III-Nitride-Based Light-Emitting Devices)

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Review

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Open AccessReview

A Review on the Progress of AlGaN Tunnel Homojunction Deep-Ultraviolet Light-Emitting Diodes

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Crystals 2023, 13(3), 524; https://doi.org/10.3390/cryst13030524 - 19 Mar 2023

Viewed by 696

Abstract

Conventional deep-ultraviolet (UV) light-emitting diodes (LEDs) based on AlGaN crystals have extremely low light-emission efficiencies due to the absorption in p-type GaN anode contacts. UV-light-transparent anode structures are considered as one of the solutions to increase a light output power. To this end, [...] Read more.

Conventional deep-ultraviolet (UV) light-emitting diodes (LEDs) based on AlGaN crystals have extremely low light-emission efficiencies due to the absorption in p-type GaN anode contacts. UV-light-transparent anode structures are considered as one of the solutions to increase a light output power. To this end, the present study focuses on developing a transparent AlGaN homoepitaxial tunnel junction (TJ) as the anode of a deep-UV LED. Deep-UV LEDs composed of n⁺/p⁺-type AlGaN TJs were fabricated under the growth condition that reduced the carrier compensation in the n⁺-type AlGaN layers. The developed deep-UV LED achieved an operating voltage of 10.8 V under a direct current (DC) operation of 63 A cm⁻², which is one of the lowest values among devices composed of AlGaN tunnel homojunctions. In addition, magnesium zinc oxide (MgZnO)/Al reflective electrodes were fabricated to enhance the output power of the AlGaN homoepitaxial TJ LED. The output power was increased to 57.3 mW under a 63 A cm⁻² DC operation, which was 1.7 times higher than that achieved using the conventional Ti/Al electrodes. The combination of the AlGaN-based TJ and MgZnO/Al reflective contact allows further improvement of the light output power. This study confirms that the AlGaN TJ is a promising UV-transmittance structure that can achieve a high light-extraction efficiency. Full article

(This article belongs to the Special Issue III-Nitride-Based Light-Emitting Devices)

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Open AccessReview

Progress of InGaN-Based Red Micro-Light Emitting Diodes

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Crystals 2022, 12(4), 541; https://doi.org/10.3390/cryst12040541 - 12 Apr 2022

Cited by 11 | Viewed by 3112

Abstract

InGaN-based red micro-size light-emitting diodes (μLEDs) have become very attractive. Compared to common AlInGaP-based red µLEDs, the external quantum efficiency (EQE) of InGaN red µLEDs has less influence from the size effect. Moreover, the InGaN red µLEDs exhibit a much more robust device [...] Read more.

InGaN-based red micro-size light-emitting diodes (μLEDs) have become very attractive. Compared to common AlInGaP-based red µLEDs, the external quantum efficiency (EQE) of InGaN red µLEDs has less influence from the size effect. Moreover, the InGaN red µLEDs exhibit a much more robust device performance even operating at a high temperature of up to 400 K. We review the progress of InGaN red μLEDs. Novel growth methods to relax the strain and increase the growth temperature of InGaN red quantum wells are discussed. Full article

(This article belongs to the Special Issue III-Nitride-Based Light-Emitting Devices)

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