Defect structure originating from threading dislocations within the GaN film grown on a convex patterned sapphire substrate

Oh, Tae Su; Jeong, Hyun; Lee, Yong Seok; Seo, Tae Hoon; Park, Ah Hyun; Kim, Hun; Lee, Kang Jea; Jeong, Mun Seok; Suh, Eun Kyung

doi:10.1016/j.tsf.2010.11.043

Cited by 19 publications

(10 citation statements)

References 20 publications

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“…Agglomerated dislocations in high density appeared in/near the LT-GaN layer due to the high lattice mismatch between the LT-GaN layer and the substrate. At the flat region, most of the vertical dislocations formed at LT-GaN bended about horizontally toward the convex dome and changed to stair-like dislocation extending askew around the slope of the convex region as reported before [9]. Also, the bent dislocations at the intersection of the convex and flat region agglomerated and transformed to staircase-like dislocations to extend along the convex region, and then converged at the top of the convex dome to form TDs (threading dislocations) through the epitaxial layers, which was described by the dotted line in Fig.…”

Section: Methodssupporting

confidence: 70%

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Microstructural analysis of InGaN/GaN epitaxial layers of metal organic chemical vapor deposition on c-plane of convex patterned sapphire substrate

Wan

Choi

et al. 2013

Thin Solid Films

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Section: Methodssupporting

confidence: 70%

“…epitaxial lateral overgrowth [4], multi-step technique [5], facet controlled epitaxial overgrowth [6], Pendeo-Epitaxy [7], GaN growth on 6H-SiC [8], sapphire, SiC and Si substrate. Also, GaN, AlN and ZnO buffer layers [9] were used to reduce the lattice mismatch of the interface between epitaxial layers and substrate.…”

Section: Introductionmentioning

confidence: 99%

Microstructural analysis of InGaN/GaN epitaxial layers of metal organic chemical vapor deposition on c-plane of convex patterned sapphire substrate

Wan

Choi

et al. 2013

Thin Solid Films

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“…Electroluminescence (EL) spectra for micro‐LEDs released from PSS and CSS are measured and plotted in Figure e. Though both LEDs are grown under the same experiment condition, the emission peak wavelength of the LED released from PSS (at 470 nm) is slightly shorter than that from CSS (at 476 nm), which is mainly caused by the stress reduction during LED growth on PSS …”

mentioning

confidence: 99%

Heterogeneous Integration of Microscale GaN Light‐Emitting Diodes and Their Electrical, Optical, and Thermal Characteristics on Flexible Substrates

Liu

et al. 2017

Adv Materials Technologies

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LEDs that can be utilized as implantable light sources have been playing increasingly important roles in neuroscience research, along with the development of genetically encoded actuators and indicators. [3,4] In particular, gallium nitride (GaN)/indium gallium nitride (InGaN) based blue LEDs are utilized as implantable light sources for optogenetic stimulation and/or exciting fluorophores for neural signal sensing. [5,6] High performance GaN blue LEDs are typically grown on rigid, single crystalline substrates including sapphire, [7,8] silicon (Si) [1] and silicon carbide (SiC), [9] and novel strategies on growing and releasing GaN devices on unusual substrates like zinc dioxide coated graphene, [10] boron nitride (BN), [11] amorphous glasses, [12] nanovoid-mediated substrates, [13] etc. are also actively explored. [14] Although diced bare LED chips have found their uses in wearable and implantable systems by flip-chip bonding, [15,16] thinfilm LEDs (with thicknesses less than 10 µm) with various emission wavelengths that are released from original growth substrates and integrated onto flexible and stretchable substrates are more desirable for biomedical applications. [17] Recent results have successfully demonstrated that released, thinfilm LEDs are integrated with flexible, stretchable, and even biodegradable substrates with better biocompatibilities like improved skin conformance and reduced lesion during implantation. [5,18,19] Thin-film, freestanding red and infrared (IR) LEDs based on gallium arsenide can be easily formed by selective sacrificial etching; [20] however, conventional techniques for thinfilm GaN based purple/blue/green LED release and integration typically rely on sophisticated process steps including laser liftoff (LLO) (for GaN on sapphire), [21,22] chemical etching (for GaN on Si), [1,23,24] wafer bonding, [25][26][27] layer transfer, [11] device pick and place, [28,29] etc., [30,31] thus limiting their use. While GaN LED epitaxial liftoff and integration with flexible substrates have been extensively exploited for various planar device architectures like GaN LEDs on graphene, [7,10] BN, [11] glasses with nanovoids, [12,13] Si, [32] SiC-on-insulator, [9] the performance of these devices is still inferior to their counterparts on conventional sapphire substrates, in terms of their current-voltage characteristics, quantum efficiencies, etc. Therefore, it is highly desirable to develop simple and reliable technologies to implement the mainstream, state-of-the-art GaN LEDs (for example,

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“…8 Second, presence of patterns considerably reduces the density of TDs in GaN layers owing to the bend of dislocations between the trench region of patterns during the epitaxial growth. 9 It was reported that the density of TDs in the GaN layer could be reduced significantly by three orders * Electrochemical Society Member.…”

mentioning

confidence: 99%

AFM and SEM Study on Crystallographic and Topographical Evolution of Wet-Etched Patterned Sapphire Substrates (PSS)

Shen

Zhang

Wang

2016

ECS J. Solid State Sci. Technol.

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A thorough understanding about the crystallographic and topographical evolution of wet-etched patterned sapphire substrates (PSS) is essential for revealing the etching mechanism and critical for fabricating optimized PSS for enhanced performance of GaN-based LED devices. As the first one of a series of three papers, using complementary scanning electron microscope (SEM) and atomic force microscope (AFM), we carried out a systematic study on the crystallographic and topographical evolution of cone-shaped PSS etched with an ordinary etchant (H 2 SO 4 :H 3 PO 4 = 3:1 at volume ratio, 230 • C) which enables crystallographic specific etching. The topography of patterns was found to evolve from normal cones to truncated cones, to triangular pyramids with multiple families of exposed crystallographic planes, then to hexagonal and triangular pyramids with a single family of planes. The Miller indexes of three major exposed crystallographic planes, with decreasing slant angles, were determined to be {11 0 5}, {45 1 38} and {11 0 12} with the last two being reported for the first time to our best knowledge. It was clearly demonstrated that AFM, thanks to its 3D topography imaging capability compared to SEM and focused ion beam, can be an indispensable tool for fast and reliable characterization of routine PSS samples.

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Defect structure originating from threading dislocations within the GaN film grown on a convex patterned sapphire substrate

Cited by 19 publications

References 20 publications

Microstructural analysis of InGaN/GaN epitaxial layers of metal organic chemical vapor deposition on c-plane of convex patterned sapphire substrate

Microstructural analysis of InGaN/GaN epitaxial layers of metal organic chemical vapor deposition on c-plane of convex patterned sapphire substrate

Heterogeneous Integration of Microscale GaN Light‐Emitting Diodes and Their Electrical, Optical, and Thermal Characteristics on Flexible Substrates

AFM and SEM Study on Crystallographic and Topographical Evolution of Wet-Etched Patterned Sapphire Substrates (PSS)

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