Improvement of efficiency droop of GaN-based light-emitting devices by a rear nitride reflector

Cai, Li-E; Zhang, Baoping; Zhang, Jiangyong; Wu, ChaoMin; Jiang, Fang; Hu, Xiaolong; Chen, Ming; Wang, Qiming

doi:10.1016/j.physe.2010.07.071

Cited by 5 publications

(5 citation statements)

References 13 publications

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“…This method of fabricating a top and bottom dielectric distributed Bragg reflector (DBR) was used for VCSEL structures. The embedded DBR structures were explored including epitaxial AlGaN/AlN DBR, epitaxial AlInN/GaN DBR, air gap/GaN DBR, and porous-GaN/GaN DBR. , However, the significant lattice mismatch and minimal difference in refractive indices in AlGaN-based DBRs made their manufacturing challenging. In the case of the air gap/GaN DBR, despite a significant difference in the refractive indices of air and GaN, the lack of mechanical strength in the air gap/GaN DBR presented challenges for optical device applications.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Vertical InGaN Light-Emitting Diode with Hybrid Distributed Bragg Reflectors

Shiu,

Ke,

Chen

et al. 2024

ACS Omega

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A vertical-type InGaN light-emitting diode with a resonant cavity was demonstrated with a 9 μm aperture size and a short cavity formed by hybrid distributed Bragg reflectors (DBRs). The approach involved designing epitaxial structures and utilizing an electrochemical etching process to convert heavily doped n-type gallium nitride (n + -GaN) layers into porous GaN layers as a porous-GaN DBR structure. Thirteen pairs of the conductive porous-GaN:Si/GaN:Si DBR structure provided a vertical current path in a vertical-type light-emitting diodes (LED) structure. The LED epitaxial layers were separated from sapphire for membranetype LED structures through a laser lift-off process. During the free-standing membrane fabrication process, the dielectric DBR deposited on ITO/p-GaN:Mg layers was inverted from top to bottom, thereby establishing the concept of higher reflectivity for the bottom DBR compared to the porous-GaN DBR. The physical cavity length was reduced from about 2.3 μm for the LED membrane to 0.74 μm for the membrane-type LED with the embedded porous-GaN DBR structure. The divergent angles and line width of EL emission light were reduced from 124°/31.7 nm to 44°/3.3 nm due to the resonant cavity effect. The membrane-type LED structures with hybrid DBRs consisted of small divergent angles, narrow line width, and vertical current injection properties that have potential for directional emission light sources and verticalcavity surface-emitting diode laser applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Vertical InGaN Light-Emitting Diode with Hybrid Distributed Bragg Reflectors

Shiu,

Ke,

Chen

et al. 2024

ACS Omega

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“…In the past two decades, III-Nitride DBRs have been applied in LEDs to improve the light output [1][2][3][4] or even in vertical-cavity surface-emitting lasers as resonant cavities [5]. Due to the important advantage in that III-Nitride DBRs can be fabricated by in situ epitaxy, many approaches have been adopted such as AlN/GaN [6][7][8][9][10], AlGaN/GaN [11,12], AlGaN/AlN [13][14][15][16], AlInN/GaN [17][18][19], AlInN/AlGaN [20,21] and so on.…”

Section: Introductionmentioning

confidence: 99%

“…Ive et al deposited 20.5 periods of AlN/GaN DBRs on SiC substrates, which had a stop band width of 40~50 nm and a maximum measured reflectance of 99% [22]. Cai et al deposited 25-pair AlN/GaN DBRs on sapphire with the reflectivity exceeding 90%, and the DBR-based LED showed a super-linear increase up to a current density of 135 A/cm 2 and the relative external quantum efficiency (EQE) kept monotonously increasing with the increase in injection current density [3]. Mastro et al grew 5-pair AlN/GaN DBRs with the peak reflectivity of 69.8% on Si substrates, while the LED structure was not deposited [23].…”

Section: Introductionmentioning

confidence: 99%

Light Output Enhancement of GaN-Based Light-Emitting Diodes Based on AlN/GaN Distributed Bragg Reflectors Grown on Si (111) Substrates

2020

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Due to the absorption of opaque Si substrates, the luminous efficiency of GaN-based light-emitting diodes (LEDs) on Si substrates is not high. So, in this work, we insert AlN/GaN distributed Bragg reflectors (DBRs) to improve the light output of GaN-based LEDs on Si (111) substrates grown via metal organic chemical vapor deposition (MOCVD). In order to obtain the highest reflectivity of the AlN/GaN DBR stop band, the growth parameters of AlN/GaN DBRs are optimized, including the growth temperature, the V/III ratio and the growth pressure. As a consequence, the interfaces of the optimal 9-pair AlN/GaN DBRs become abrupt, and the reflectivity of the DBR stop band is as high as 85.2%, near to the calculated value (92.5%). Finally, crack-free GaN-based LEDs with 5-pair AlN/GaN DBRs are grown on Si (111) substrates. The light output of the DBR-based LED is evidently enhanced by 41.8% at the injection current of 350 mA, compared with the conventional DBR-based LED without DBRs. These results pave the way for the luminous efficiency improvement of future green and red GaN-based LEDs grown on Si substrates.

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“…Nevertheless, in most reports of AlN-GaN-based (AlN/GaN, AlGaN/GaN or AlGaN/AlN) DBRs, the DBRs were deposited on sapphire substrates. [11][12][13][14][15][16][17][18] There are very few reports of DBRs on Si substrates [19][20][21] because the DBRs would induce tensile stress, leading to crack formation. Regarding AlN-GaN-based DBRs on Si substrates, Ishikawa et al 20) achieved crack-free DBR-based LEDs on Si substrates, but only three pairs of DBR structures were fabricated, and vertical-conducting DBR-LEDs were not realized, because of the insulating AlN and high-resistivity AlGaN layers and the large band offset at the AlN/Si interface.…”

mentioning

confidence: 99%

Vertical-conducting InGaN/GaN multiple quantum wells LEDs with AlN/GaN distributed Bragg reflectors on Si(111) substrate

Yang

Lin

Xiang

et al. 2014

Appl. Phys. Express

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In this study, crack-free InGaN/GaN multiple quantum well (MQW) LEDs with five-pair AlN/GaN distributed Bragg reflectors (DBRs) were grown on a Si(111) substrate using a linear compositionally graded AlGaN layer to compensate for tensile stresses. DBR-based LEDs exhibited higher light efficiency and better crystalline quality than non-DBR-based LEDs. Vertical-conducting DBR-based LEDs were realized using through-hole structure. Through-holes were formed from the n-GaN layer to the Si substrate and filled with metals, which connected the n-GaN layer and the Si substrate. Insulating AlN, high-resistivity AlGaN layers, and the large band offset at the AlN/Si interface were all shorted by the metal filled into the through-holes. Compared to DBR-based LED without through-holes, DBR-based LEDs with through-holes exhibited significantly better electrical and optical properties.

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Improvement of efficiency droop of GaN-based light-emitting devices by a rear nitride reflector

Cited by 5 publications

References 13 publications

Vertical InGaN Light-Emitting Diode with Hybrid Distributed Bragg Reflectors

Vertical InGaN Light-Emitting Diode with Hybrid Distributed Bragg Reflectors

Light Output Enhancement of GaN-Based Light-Emitting Diodes Based on AlN/GaN Distributed Bragg Reflectors Grown on Si (111) Substrates

Vertical-conducting InGaN/GaN multiple quantum wells LEDs with AlN/GaN distributed Bragg reflectors on Si(111) substrate

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