Highly efficient and reliable high power LEDs with patterned sapphire substrate and strip-shaped distributed current blocking layer

Zhou, Shengjun; Yuan, Shijian; Liu, Yingce; Guo, L. Jay; Liu, Sheng; Ding, Han

doi:10.1016/j.apsusc.2015.07.194

Cited by 74 publications

(28 citation statements)

References 34 publications

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“…Usually sapphire, Si or SiC substrates are used. One of the main problems remains the difference in lattices of nitrides and a foreign substrate that leads to the rise of a high number of threading dislocations on the interface [1]. Usually a well-described procedure of the growth of a low temperature AlN or GaN buffer layer is used, which involves a low temperature nucleation layer and a consecutive coalescence layer [2].…”

Section: Introductionmentioning

confidence: 99%

Improvement of GaN crystalline quality by SiN_x layer grown by MOVPE

Hospodková¹,

Zíková²,

Hubáček³

et al. 2020

physics

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In this work the mechanism which helps to reduce the dislocation density by deposition of a SiNx interlayer is discussed. It is shown that the dislocation reduction by SiNx interlayer deposition is influenced by dislocation density in the underlying GaN layers. The SiNx interlayer is very effective when the original dislocation density is high, while in the case of lower dislocation density the deposition of SiNx is not effective for crystal quality improvement. Although it is widely accepted that SiNx serves as a barrier for dislocation propagation, similarly to the enhanced lateral overgrowth method, it is shown that after masking the SiNx deposition cannot be the dominant dislocation reduction mechanism. The most probable mechanism is the annihilation of bended neighbouring dislocations during the coalescence of 3D islands. The SiNx layer cannot serve as a barrier for dislocations, since it is probably dissolved during the following GaN growth and dissolved Si atoms are incorporated into the above-grown GaN layer which stimulates the 3D island formation. Then the use of the SiNx interlayer for dislocation reduction is recommended only for the improvement of layers with a high dislocation density. On the other hand, the PL signal was strongly enhanced for both low and high dislocation density structures with the SiNx interlayer, suggesting that the interlayer might help to suppress the nonradiative recombination in subsequent GaN that is not related to the dislocation density, which remained the same. But its origin has to be studied further.

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Section: Introductionmentioning

confidence: 99%

Improvement of GaN crystalline quality by SiN_x layer grown by MOVPE

Hospodková¹,

Zíková²,

Hubáček³

et al. 2020

physics

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“…GaN-based LEDs are typically grown on sapphire substrate that is electrically insulating so both p-type and n-type contacts are located on the same side of top-emitting LEDs, resulting in current crowding effect around electrode pads. Most scientific efforts have therefore focused on one approach to alleviate the current crowding effect: using insulating SiO 2 as current blocking layer [4,5]. In this scheme, an insulating SiO 2 layer inserted beneath the indium-tin oxide (ITO) was used to uniformly redirect the current path and thus improve current spreading.…”

Section: Introductionmentioning

confidence: 99%

GaN-based flip-chip LEDs with highly reflective ITO/DBR p-type and via hole-based n-type contacts for enhanced current spreading and light extraction

Zhou

Zheng

et al. 2017

Optics & Laser Technology

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We demonstrate GaN-based double-layer electrode flip-chip light-emitting diodes (DLE-FCLED) with highly reflective indium-tin oxide (ITO)/distributed bragg reflector (DBR) p-type contact and via hole-based n-type contacts. Transparent thin ITO in combination with TiO 2 /SiO 2 DBR is used for reflective p-type ohmic contact, resulting in a significant reduction in absorption of light by opaque metal electrodes. The finely distributed via hole-based n-type contacts are formed on the n-GaN layer by etching via holes through p-GaN and multiple quantum well (MQW) active layer, leading to reduced lateral current spreading length, and hence alleviated current crowding effect. The forward voltage of the DLE-FCLED is 0.31 V lower than that of the top-emitting LED at 90 mA. The light output power of DLE-FCLED is 15.7% and 80.8% higher than that of top-emitting LED at 90 mA and 300 mA, respectively. Compared to top-emitting LED, the external quantum efficiency (EQE) of DLE-FCLED is enhanced by 15.4% and 132% at 90 mA and 300 mA, respectively. The maximum light output power of the DLE-FCLED obtained at 195.6 A/cm 2 is 1.33 times larger than that of the top-emitting LED obtained at 93 A/cm 2 .

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“…The EQE equals the multiplication of the internal quantum efficiency (IQE) and the light extraction efficiency (LEE) [6]. Since micro-LEDs are obtained from an identical wafer as large scale LEDs, the fruitful methods for improving IQE of large scale LEDs are also applicable for micro-LEDs [7][8][9][10][11]. However, the ratio of sidewall emitting area to top emitting area is greatly different for micro-LEDs…”

Section: Introductionmentioning

confidence: 99%

Light Extraction Analysis of AlGaInP Based Red and GaN Based Blue/Green Flip-Chip Micro-LEDs Using the Monte Carlo Ray Tracing Method

et al. 2019

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Micro-scale light emitting diodes (micro-LEDs) commonly employ a thin-film flip-chip (TFFC) structure whose substrate is lifted off by an excimer laser. However, flip-chip (FC) micro-LEDs with a substrate can provide a sharp rise on sidewall emission by increasing the sidewall area. Here, we investigate the influence of substrate thickness, encapsulation, surface texture, microstructures between the substrate and epilayer, as well as the size, cutting shape, and angle of the chip on the light extraction efficiencies (LEEs) of FC micro-LEDs by using the Monte Carlo ray tracing method. We find that the LEE of the blue FC micro-LED chip increases by 46.5% over that of the blue TFFC micro-LED chip. After the encapsulation with the epoxy lens is applied, the LEEs of the blue TFFC micro-LED and blue FC micro-LED increase by 129% and 110.5%, respectively. The underlying mechanisms for the use of surface texture, patterned sapphire substrate, air-void array, and chip shaping technologies to improve the LEEs of FC micro-LEDs are also investigated in detail. We find that the LEEs AlGaInP based red FC micro-LED and GaN based blue/green FC micro-LEDs exhibit a sharp rise when the chip size drops from 30 to 10 µm. The inverted trapezoid FC micro-LED with patterned sapphire substrate (PSS) and encapsulation shows extraordinarily strong top emission and high collimation. We believe that our study offers a promising and practical route for obtaining high efficiency micro-LEDs.

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Highly efficient and reliable high power LEDs with patterned sapphire substrate and strip-shaped distributed current blocking layer

Cited by 74 publications

References 34 publications

Improvement of GaN crystalline quality by SiN_x layer grown by MOVPE

Improvement of GaN crystalline quality by SiN_x layer grown by MOVPE

GaN-based flip-chip LEDs with highly reflective ITO/DBR p-type and via hole-based n-type contacts for enhanced current spreading and light extraction

Light Extraction Analysis of AlGaInP Based Red and GaN Based Blue/Green Flip-Chip Micro-LEDs Using the Monte Carlo Ray Tracing Method

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Highly efficient and reliable high power LEDs with patterned sapphire substrate and strip-shaped distributed current blocking layer

Cited by 74 publications

References 34 publications

Improvement of GaN crystalline quality by SiNx layer grown by MOVPE

Improvement of GaN crystalline quality by SiNx layer grown by MOVPE

GaN-based flip-chip LEDs with highly reflective ITO/DBR p-type and via hole-based n-type contacts for enhanced current spreading and light extraction

Light Extraction Analysis of AlGaInP Based Red and GaN Based Blue/Green Flip-Chip Micro-LEDs Using the Monte Carlo Ray Tracing Method

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Improvement of GaN crystalline quality by SiN_x layer grown by MOVPE

Improvement of GaN crystalline quality by SiN_x layer grown by MOVPE