Large-area transparent conductive few-layer graphene electrode in GaN-based ultra-violet light-emitting diodes

Kim, Byung Jae; Lee, Chong Min; Jung, Younghun; Baik, Kwang Hyeon; Mastro, Michael A.; Hite, Jennifer K.; Eddy, Charles R.; Kim, Jihyun

doi:10.1063/1.3644496

Cited by 102 publications

(87 citation statements)

References 18 publications

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“…Compared with the graphene prepared on SiO 2 , the graphene on the Si wafer exhibited multiple layers. Largearea graphene wafers are mostly grown on Cu foils, resulting in polycrystalline samples with a substantial number of grain boundaries, which are detrimental to the electronic properties [9]. The polarization of SiO 2 supported the formation of monolayer graphene.…”

Section: Resultsmentioning

confidence: 99%

“…CVD requires catalytic metal films such as Ni and Cu, and posttransfer techniques are required to support the graphene on a substrate. Therefore, it is desirable to control the strength of graphene-metal interactions to facilitate graphene characterization and processing [9,10]. Both theoretical and experimental studies have revealed that the chemical doping of graphene with foreign atoms such as nitrogen, boron, and sulfur can be used to define the electronic properties and chemical reactivity [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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CVD Graphene Synthesis on Copper Foils and Doping Effect by Nitric Acid

오데레사¹

2013

Transactions on Electrical and Electronic Materials

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Graphene was obtained on Cu foil by thermal decomposition method. A gas mixture of H 2 and CH 4 and an ambient annealing temperature of 1,000℃ were used during the deposition for 30 Min., and for the transfer onto SiO 2 /Si and Si substrates. The physical properties of graphene were investigated with regard to the effect ofnitrogen atom doping and the various substrates used. The G/2D ratio decreased when the graphene became monolayer graphene. The graphene grown on SiO 2 /Si substrate showed a low intensity of the G/2D ratio, because the polarity of the SiO 2 layer improved the quality of graphene. The intensity of the G/2D ratio of graphene doped with nitrogen atoms increased with the doping time. The quality of graphene depended on the concentration of the nitrogen doping and chemical properties of substrates. High-quality monolayer graphene was obtained with a low G/2D ratio. The increase in the intensity of the G/2D ratios corresponded to a blue shift in the 2D peaks.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

CVD Graphene Synthesis on Copper Foils and Doping Effect by Nitric Acid

오데레사¹

2013

Transactions on Electrical and Electronic Materials

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“…The SF 6 plasma treatment (namely, F-doping) increased the work function and bandgap of ITO films and accordingly improved the electrical and optical properties. The specific contact resistance and transmittance of optimal F-doped ITO were measured to be 9.12 × 10 65 However, the LEDs with few-layer GR had a high forward voltage larger than 10 V at 2 mA and were burnt out at high current injection. Thus, to improve the contact resistance and the stability of nanomaterialbased TCEs, various techniques, including interface engineering, [69][70][71][72][73][74][75][76][77][78] hybrid nanomaterial structures, [79][80][81][82][83] and chemical doping, [84][85][86][87] have been extensively studied.…”

Section: Ohmic Contacts To P-gan For Near Uv Ledsmentioning

confidence: 99%

Review—Group III-Nitride-Based Ultraviolet Light-Emitting Diodes: Ways of Increasing External Quantum Efficiency

Park

Kim

Cho

et al. 2017

ECS J. Solid State Sci. Technol.

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There is a rapidly growing demand for highly efficient ultraviolet (UV) light sources for a wide variety of applications. In particular, state-of-the-art AlGaN deep UV light-emitting diodes (DUV LEDs) exhibit inadequately low external quantum efficiencies (EQEs). The low efficiencies are attributed to the inherent material properties of high-Al-content AlGaN including strained epitaxial layers, low carrier concentrations, and strong transverse magnetic (TM)-polarized light emission. Extensive efforts have been made to tackle these challenging issues and technological developments have been achieved and enabled the fabrication of reasonable EQE LEDs. In this review, recent advances in the growth of high-quality AlGaN epitaxial layers, transparent and reflective ohmic contacts, and light extraction for AlGaN-based UV LEDs are reviewed. Al x Ga 1-x N-based ultraviolet light-emitting diodes (UV LEDs) are of technological importance because of their applications in numerous areas such as water purification, biological analysis, sensing, epoxy curing, high-density optical storage, white light illumination, UV adhesives, 3-dimensional (3D) printer and UV-coating.1,2 These applications are made possible because of their wide bandgap energy range in the UV spectrum, which spans from 6.2 eV (AlN) to 3.4 eV (GaN), namely, from UV-A (320-400 nm), UV-B (290-320 nm) to UV-C (200-290 nm).3-7 The external quantum efficiency (EQE) of Al x Ga 1-x N-based UV LEDs decreases rapidly as the molar fraction (x) of Al increases, namely, as the wavelength decreases, as illustrated in Figure 1. 8 Thus, a great deal of effort has been made in order to improve the EQE of UV LEDs. The effort notwithstanding, however, the EQE of AlGaN-based UV LEDs is still insufficiently low. The typical EQE of UV LEDs, specifically in the UV-C spectral range (100-280 nm), is less than 5% and decreases down to 10 -6 % for 210-nm AlN-based UV LEDs. 4 These low EQEs are associated with the intrinsic material properties of Al x Ga 1-x N.1,2 Figure 2 exhibits a schematic diagram of a typical AlGaN UV LED structure grown on a sapphire substrate. The structure consists of a Si-doped n-type AlGaN, an Al x Ga 1-x N/Al y Ga 1-y N multiple-quantum well (MQW) active region, an AlGaN-based electron-blocking layer (EBL), a Mg-doped p-type AlGaN, and a Mg-doped p-type GaN. Almost every layer in the structure poses different technical issues, which limit the efficiency of UV LEDs, as shown in Figure 2. First, increasing the Al content generally results in a poor crystallinity of AlGaN epilayers, causing a poor internal quantum efficiency (IQE). Second, both n-type and ptype doping efficiencies of AlGaN are difficult to increase because the ionization energies of acceptor (Mg) and donor (Si) dopants largely increase with increasing Al content. The low doping efficiency causes several technological problems: (i) a poor electrical efficiency (EE) attributable to high-resistance contacts on resistive n-type and p-type AlGaN; (ii) current crowding causing non-uniform current in...

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“…However, it is not appropriate for ultraviolet (UV) GaN LED [12,13]. In addition, the price of the ITO has been increasing for scarce of indium [14][15][16][17]. What's more, ITO is unstable in chemical solutions [12,15,16].…”

Section: Introductionmentioning

confidence: 99%

“…What's more, ITO is unstable in chemical solutions [12,15,16]. Graphene, a 2D monolayer of carbon atoms, has recently attracted tremendous attention for its excellent optical, mechanical, and electrical properties, such as high transparency in the UV region, ultra-fast mobility, high thermal conductivity, and high mechanical strength [12][13][14][15][16][17][18]. It may be used as an alternative to the ITO in LED.…”

Section: Introductionmentioning

confidence: 99%

Enhanced performance of photonic crystal GaN light-emitting diodes with graphene transparent electrodes

葛海亮¹,

许坤²,

徐晨³

2016

Nano Online

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The two-dimensional (2D) triangle lattice air hole photonic crystal (PC) GaN-based light-emitting diodes (LED) with double-layer graphene transparent electrodes (DGTE) have been produced. The current spreading effect of the double-layer graphene (GR) on the surface of the PC structure of the LED has been researched. Specially, we found that the part of the graphene suspending over the air hole of the PC structure was of much higher conductivity, which reduced the average sheet resistance of the graphene transparent conducting electrode and improved the current spreading of the PC LED. Therefore, the work voltage of the DGTE-PC LED was obviously decreased, and the output power was greatly enhanced. The COMSOL software was used to simulate the current density distribution of the samples. The results show that the etching of PC structure results in the degradation of the current spreading and that the graphene transparent conducting electrode can offer an uniform current spreading in the DGTE-PC LED.

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Large-area transparent conductive few-layer graphene electrode in GaN-based ultra-violet light-emitting diodes

Cited by 102 publications

References 18 publications

CVD Graphene Synthesis on Copper Foils and Doping Effect by Nitric Acid

CVD Graphene Synthesis on Copper Foils and Doping Effect by Nitric Acid

Review—Group III-Nitride-Based Ultraviolet Light-Emitting Diodes: Ways of Increasing External Quantum Efficiency

Enhanced performance of photonic crystal GaN light-emitting diodes with graphene transparent electrodes

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