Study of the structural damage in the (0001) GaN epilayer processed by laser lift-off techniques

Chen, W. H.; Kang, Xiaoning; Hu, Xiaodong; Lee, R.; Wang, Y. J.; Yu, Tongjun; Zhi‐Jian, Yang; Zhang, G. Y.; Shan, Li; Liu, K. X.; Shan, Xudong; You, Long; Yu, Dapeng

doi:10.1063/1.2783134

Cited by 40 publications

(33 citation statements)

References 22 publications

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“…As the dislocation density of the GaN layer near the substrate is well known to be increased after the LLO of the sapphire substrate, 5,9 we have considered the dislocation formation deep in the bottom n-GaN layer. out from top to the bottom without removing the sapphire substrate and (b) when the bottom n-GaN layer is etched out by a thickness amount of 2 μm after the LLO.…”

Section: Resultsmentioning

confidence: 99%

“…This fact manifests that the atomic movements needed for the observed dislocation generation and MQW intermixing are mainly due to the combined effects of REDR and the phonon generation as the generated electrons and holes move to their relevant band edges to recombine, while many people have argued that the generation and propagation of shock wave at/from the GaN/Al 2 O 3 interface would be the main origin of the increase of the dislocations in the bottom GaN layer after the LLO process. [5][6][7] This reasoning can also explain how the QW intermixing may be so apparent even with a rather small number of the KrF photons arriving at the MQWs (1.5 × 10 16 /cm 2 ). The difference between the KrF photon energy and the bandgap energy of GaN (In 0.3 Ga 0.7 N) is 1.6 (2.2) eV.…”

Section: Fig 5 (A)mentioning

confidence: 99%

“…2 Recently, many works have been reported on the vertical InGaN/GaN LED structure for which the sapphire substrate is removed using a laser lift-off (LLO) technique and carrier materials such as Cu or Si are employed on top of the LEDs for the LLO process. [4][5][6][7][8] The resulting vertical LEDs show an improved high current operation capability than conventional LEDs. 4 However, a high power KrF UV laser which is usually employed for the LLO process is known to affect the material properties of the InGaN/GaN LED structures.…”

Section: Introductionmentioning

confidence: 99%

“…4 However, a high power KrF UV laser which is usually employed for the LLO process is known to affect the material properties of the InGaN/GaN LED structures. [5][6][7][8] Chen et al have reported that, in addition to the superficial damage caused by KrF laser absorption, the shock waves can generate a cluster of half loops above the LLO interface. 5 The screw dislocations generated by the LLO process are believed to lead to an increase in the leakage current in the vertical LEDs.…”

Section: Introductionmentioning

confidence: 99%

“…[5][6][7][8] Chen et al have reported that, in addition to the superficial damage caused by KrF laser absorption, the shock waves can generate a cluster of half loops above the LLO interface. 5 The screw dislocations generated by the LLO process are believed to lead to an increase in the leakage current in the vertical LEDs. 6 Even though many studies have been reported on the damage effect of the LLO process on the GaN layers, 5-9 few works have been reported on the effects of the LLO process on the InGaN/GaN multiple quantum well (MQW) layers of the GaN-based LEDs.…”

Section: Introductionmentioning

confidence: 99%

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Influence of laser lift-off on optical and structural properties of InGaN/GaN vertical blue light emitting diodes

et al. 2012

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The influences of the laser lift-off (LLO) process on the InGaN/GaN blue light emitting diode (LED) structures, grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition, have been comprehensively investigated. The vertical LED structures on Cu carriers are fabricated using electroplating, LLO, and inductively coupled plasma etching processes sequentially. A detailed study is performed on the variation of defect concentration and optical properties, before and after the LLO process, employing high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) observations, cathodoluminescence (CL), photoluminescence (PL), and high-resolution X-ray diffraction (HRXRD) measurements. The SEM observations on the distribution of dislocations after the LLO show well that even the GaN layer near to the multiple quantum wells (MQWs) is damaged. The CL measurements reveal that the peak energy of the InGaN/GaN MQW emission exhibits a blue-shift after the LLO process in addition to a reduced intensity. These behaviors are attributed to a diffusion of indium through the defects created by the LLO and creation of non-radiative recombination centers. The observed phenomena thus suggest that the MQWs, the active region of the InGaN/GaN light emitting diodes, may be damaged by the LLO process when thickness of the GaN layer below the MQW is made to be 5 μm, a conventional thickness. The CL images on the boundary between the KrF irradiated and non-irradiated regions suggest that the propagation of the KrF laser beam and an accompanied recombination enhanced defect reaction, rather than the propagation of a thermal shock wave, are the main origin of the damage effects of the LLO process on the InGaN/GaN MQWs and the n-GaN layer as well

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Section: Resultsmentioning

confidence: 99%

Section: Fig 5 (A)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of laser lift-off on optical and structural properties of InGaN/GaN vertical blue light emitting diodes

et al. 2012

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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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Active‐Matrix GaN µ‐LED Display Using Oxide Thin‐Film Transistor Backplane and Flip Chip LED Bonding

Jeong

Jung

et al. 2018

Adv Elect Materials

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A 2 in. active‐matrix light‐emitting diode (AMLED) display by integration of the micro‐LED onto the oxide thin‐film transistor (TFT) backplane using flip chip bonding is reported. A blue‐emitting micro‐LED (µ‐LED) with a size of 90 × 50 µm2 is fabricated on the GaN epi grown on a sapphire substrate. The amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) TFT on glass exhibiting the mobility of 18.4 cm2 V−1 s−1, turn‐on voltage (V ON) of 0.2 V, and subthreshold swing 0.25 V dec−1, is used for LED backplane. A two TFT and one capacitance pixel structure is utilized for driving 128 × 384 AMLED with 120 Hz frame rate. The laser lift‐off process with flip‐chip bond allows the transfer of the µ‐LED chips with 49 152 pixels onto the TFT backplane, demonstrating a 2 in. AMLED display with a good gray scale image. The current efficiency of µ‐LED is found to be 12.9 Cd A−1 at the luminance of 630 Cd m−2. Therefore, a‐IGZO TFT backplane can be used for µ‐LED displays.

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Study of the structural damage in the (0001) GaN epilayer processed by laser lift-off techniques

Cited by 40 publications

References 22 publications

Influence of laser lift-off on optical and structural properties of InGaN/GaN vertical blue light emitting diodes

Influence of laser lift-off on optical and structural properties of InGaN/GaN vertical blue light emitting diodes

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

Active‐Matrix GaN µ‐LED Display Using Oxide Thin‐Film Transistor Backplane and Flip Chip LED Bonding

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