Omnidirectional Reflector with Total Internal Reflective Interface for Light Extraction Enhancement of Solid‐State Light Source

Yamae, Kazuyuki; Fukshima, Hiroshi; Fujimoto, Kozo

doi:10.1002/pssa.201700775

Cited by 9 publications

(7 citation statements)

References 21 publications

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“…Thus, depositing a reflector onto p -GaN in order to reflect photons emitted downward can significantly enhance the LEE of the FCLEDs [38]. It has been reported that various reflectors, such as metallic mirrors and dielectric distributed Bragg reflectors (DBRs), have been used to enhance the LEE of FCLEDs [39,40,41,42]. In addition, highly reflective DBRs are also important for realizing high performance vertical-cavity surface emitting laser [43,44].…”

Section: Introductionmentioning

confidence: 99%

Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Zhou

Liu

et al. 2018

Micromachines

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We demonstrated two types of GaN-based flip-chip light-emitting diodes (FCLEDs) with distributed Bragg reflector (DBR) and without DBR to investigate the effect of dielectric TiO2/SiO2 DBR on optical and electrical characteristics of FCLEDs. The reflector consisting of two single TiO2/SiO2 DBR stacks optimized for different central wavelengths demonstrates a broader reflectance bandwidth and a less dependence of reflectance on the incident angle of light. As a result, the light output power (LOP) of FCLED with DBR shows 25.3% higher than that of FCLED without DBR at 150 mA. However, due to the better heat dissipation of FCLED without DBR, it was found that the light output saturation current shifted from 268 A/cm2 for FCLED with DBR to 296 A/cm2 for FCLED without DBR. We found that the use of via-hole-based n-type contacts can spread injection current uniformly over the entire active emitting region. Our study paves the way for application of DBR and via-hole-based n-type contact in high-efficiency FCLEDs.

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Section: Introductionmentioning

confidence: 99%

Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Zhou

Liu

et al. 2018

Micromachines

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“…over a 2.5 GHz to 3.5 GHz frequency range with 13.5 ± 1.0 dB gain. The maximum output power density of 4.15 W/mm is comparable with commercially available GaN HEMTs e.g., Wolfspeed CGH6008D 3.8 W/mm (Durham, NC, USA) [40], Qorvo TGF2023-2-01 4.8 W/mm) (Greensboro, NC, USA) [41].…”

Section: Design and Fabrication Of The On Microwave Power Amplifier Umentioning

confidence: 56%

Wide Bandgap Semiconductor Based Micro/Nano Devices

Seo¹

2019

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While conventional group IV or III-V based device technologies have reached their technical limitations (e.g., limited detection wavelength range or low power handling capability), wide bandgap (WBG) semiconductors which have band-gaps greater than 3 eV have gained significant attention in recent years as a key semiconductor material in high-performance optoelectronic and electronic devices [1,2]. These WBG semiconductors have various definitive advantages for optoelectronic and electronic applications due to their large bandgap energy. WBG energy is suitable to absorb or emit ultraviolet (UV) light in optoelectronic devices [3]. It also provides a higher electric breakdown field, which allows electronic devices to possess higher breakdown voltages [4]. In this Special Issue, 13 papers published, including various AlGaN/GaN, SiC, and WO 3 based devices. More than half of papers reported recent progress on AlGaN/GaN high electron mobility transistors (HEMTs) and light emitting diodes (LEDs). Wojtasiak et al., and Sun et al, reported a structural modification of AlGaN/GaN HEMTs to improve turn-on voltage, contact resistance, and on-resistance [5]. Huang et al. investigated high-temperature characteristics of AlGaN/GaN HEMTs and successfully established the thermal model [6]. Mao et al. and Li et al. simulated AlGaN/GaN HEMTs with a large signal model to investigate the kink-effect [7,8]. All of these efforts toward AlGaN/GaN HEMTs enable readers to understand current issues in AlGaN/GaN HEMTs and offer various experimental and theoretical solutions. Beside transistor works, flip-chip GaN LEDs that were combined with TiO 2 /SiO 2 distributed Bragg reflectors (DBRs) was reported by Zhou et al [9]. An improved GaN HEMTs and their microwave performance by employing the asymmetric power-combining was reported by Kim et al [10]. Along with another GaN LED built on a modified micron-size patterned sapphire substrate by Hsu et al. [11]. These GaN LED works are also guided broad readers in the field of optoelectronics and biomedical areas toward future high-performance optogenetics and photonics applications. Also, Sun et al. reported an enhanced AlGaN/GaN Schottky Barrier by engineering the structure of the diode [12]. In addition to AlxGa1-xN system, two SiC simulation efforts have been made by Huang et al. and Jia et al. Huang. They focused on the improvement of higher added efficiency (PAE) factor in 4H-SiC metal semiconductor field effect transistors and breakdown voltage of 4H-SiC diodes, respectively [13,14]. Besides popular AlxGa1-xN and SiC-based applications, three papers report InGaZnO thin-film transistors (TFTs), Si/GaP one-transistor dynamic random-access memory (1T DRAM), and WO 3 thin-film. Zhou et al. investigated a stress tolerance of InGaZnO TFTs with a SiO 2 or Al 2 O 3 passivation layer which shows a stable positive bias during the operation [15]. Kim et al. simulated a novel 1T DRAM design by inserting a GaP pillar which showed a stable high-temperature operation [16]. Finally, Zhang et al. reported th...

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“… is the incident angle to the reflector. The causal relationship between the microstructure and reflectance of the backside mirror has been already reported with the optical simulation of the LEE [21].…”

Section: Simulationmentioning

confidence: 58%

“…Total internal reflective omnidirectional reflector (TI-ODR) which is designed to utilize TIR of wide angular incident light by low-index thick layer was developed. The angular integrated reflectance of TI-ODR reached to 99.7% and indicated LEE enhancement effect of solid-state lighting devices [21]. However, since the multi-layer structure was optimized to maximize optical property, the other properties are insufficient for device and application.…”

Section: Introductionmentioning

confidence: 99%

Omnidirectional Reflector based on Transparent Oxide Materials for Light Extraction Enhancement of Organic and Inorganic Solid-state Light Emitting Devices

Yamae

Fukshima

Iwahashi

et al. 2018

J. Photopol. Sci. Technol.

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High performance reflector is significant structure for efficiency improvement of organic and inorganic solid-state light emitting devices because a large difference in the refractive index between the light source and air leads to multiple internal reflections at the reflector. Then we focused on wide angular light incidence and designed a total internal omnidirectional reflector (TI-ODR) based on transparent oxide layers. The simulation results showed that light extraction structure with TI-ODR gives 17% and 4% efficiency enhancement compared to typical Ag based mirror for organic LED (n=1.8) and inorganic LED (n=2.4), respectively. Then the TI-ODR on blue LED structure was fabricated and that showed enhancement effect of about 8%. The layers are composed of conductive layer for current distribution, low-index thick layer for total internal reflection (TIR) of wide angular light, and high-index layer for the reinforcement of adhesion of layers.

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Omnidirectional Reflector with Total Internal Reflective Interface for Light Extraction Enhancement of Solid‐State Light Source

Cited by 9 publications

References 21 publications

Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Wide Bandgap Semiconductor Based Micro/Nano Devices

Omnidirectional Reflector based on Transparent Oxide Materials for Light Extraction Enhancement of Organic and Inorganic Solid-state Light Emitting Devices

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