Optimization of current spreading metal layer for GaN/InGaN-based light emitting diodes

Cao, X. A.; Stokes, E. B.; Sandvik, Peter; Taskar, N. R.; Kretchmer, J.; Walker, D.

doi:10.1016/s0038-1101(02)00023-0

Cited by 43 publications

(27 citation statements)

References 13 publications

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“…The performance of LED devices with a mesa structure depends on lateral carrier injection. However, the major problem of using the lateral carrier injection is that it can lead to a non-uniform current spreading in the GaN based LEDs [12,13]. Non-uniform current spreading can significantly degrade the performance of GaN-based LED in that the current becomes overcrowded in a localized region of the device.…”

Section: Introductionmentioning

confidence: 99%

Effects of Current Spreading in GaN-based Light-emitting Diodes Using ITO Spreading Pad

Kim¹,

Kım²,

Park³

et al. 2015

JSTS:Journal of Semiconductor Technology and Science

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Abstract-In conventional LEDs, a mesa-structure is usually used and it causes the current to be overcrowded in a specific region. We propose a novel structure of GaN-based LED to overcome this problem. In order to distribute the current in an active region, a spreading pad is inserted at the p-type region in the GaN based LED device. The inserted spreading pad helps the current flow because it is more conductive than the p-type GaN layer. By performing electrical and optical simulations, the effects of the spreading pad insertion are confirmed. The results of electrical simulation show that the current spreads more uniformly and more radiative recombination is produced as well. Moreover, from the optical simulation, it is revealed that the ITO is less absorptive material than p-GaN if the condition of specific wavelength sources is satisfied. Considering all of the results, we can conclude that the luminescent power is enhanced by the spreading pad.

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Section: Introductionmentioning

confidence: 99%

Effects of Current Spreading in GaN-based Light-emitting Diodes Using ITO Spreading Pad

Kim¹,

Kım²,

Park³

et al. 2015

JSTS:Journal of Semiconductor Technology and Science

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“…Conventional blue and green LEDs employ a thin oxidized Ni/Au electrode formed on low-conductivity p-GaN, acting as the p-type ohmic contact and current spreader as well as a light-extraction window. 5,6 However, there exists a trade-off between the conductivity and transparency of the Ni/Au contact. While thick Ni/Au films are necessary to achieve uniform current spreading, thinner contacts are desirable from the light-extraction standpoint.…”

Section: Introductionmentioning

confidence: 99%

“…While thick Ni/Au films are necessary to achieve uniform current spreading, thinner contacts are desirable from the light-extraction standpoint. 6 The transmittance of typical Ni/Au semitransparent contacts at blue wavelengths is below 80%, limiting the light extraction and overall external efficiencies of LEDs. 6,7 Thinner and more transparent Ni/Au contacts, however, may not be capable of carrying high currents, posing a significant reliability challenge.…”

Section: Introductionmentioning

confidence: 99%

“…6 The transmittance of typical Ni/Au semitransparent contacts at blue wavelengths is below 80%, limiting the light extraction and overall external efficiencies of LEDs. 6,7 Thinner and more transparent Ni/Au contacts, however, may not be capable of carrying high currents, posing a significant reliability challenge. 8 Recently, ohmic contacts based on indium tin oxide (ITO) were developed to replace the semitransparent Ni/Au contacts in GaN-based LEDs.…”

Section: Introductionmentioning

confidence: 99%

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Au-Doped Indium Tin Oxide Ohmic Contacts to p-Type GaN

Guo

Andagana

Cao

2010

Journal of Elec Materi

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Indium tin oxide (ITO) thin films doped with Au, Ni, or Pt (3.5 at.% to 10.5 at.%) were deposited on p-GaN epilayers (Mg $4 9 10 19 cm À3 ) using direct-current (DC) sputter codeposition. It was found that undoped ITO contacts to p-GaN exhibited leaky Schottky behavior, whereas the incorporation of a small amount of Au (3.5 at.% to 10.5 at.%) significantly improved their ohmic characteristics. Compared with standard Ni/ITO contacts, the Au-doped ITO contacts had a similar specific contact resistance in the low 10 À2 X cm À2 range, but were more stable above 600°C and more transparent at blue wavelengths. These results provide support for the use of Au-doped ITO ohmic contact to p-type GaN in high-brightness blue light-emitting diodes.

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“…Development of high brightness LED was an important way to expand the LED application market [6 -8]. The uniformity of injection current in large area chip [9,10] and heat sinking of the packaging [11] must be considered in the power LED designing. On the other hand, few works were reported on the properties and stability of GaN-based power LED [12,13], which was very important for further designing.…”

Section: Introductionmentioning

confidence: 99%

Study on the stability of the high‐brightness white LED

Chen

Zhao

Qin

et al. 2004

Physica Status Solidi (b)

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The high-power white light emitting diode (LED) is packaged by GaN-based blue LED chip with the size of 1 × 1 mm 2 , YAG : Ce yellow fluorescer, epoxy and an effective heat sinking. The wavelength of the LED chip emission blue-shifts from 482 to 475 nm, while that of the fluorescer emission does not change in electroluminescence (EL) spectrum when the injection current increases from 5 to 200 mA. And the correlated color temperature decreases from 5300 to 4800 K. When the injection current increases to 200 mA, the luminous power (P e ) increases to 13.8 mW, which is about 10 times of those of the normal size (0.3 × 0.3 mm 2 ) diodes fabricated with the same wafer and same injection density. P e and forward bias (V f ) at 200 mA are measured for the aging high-power white LED. At the beginning, P e decreases dramatically 20% and V f decreases about 0.2 V in 2 days. And then P e and V f decrease slowly in the remaining 79 days aging. The contact metals electro migration along the channels induced by the threading dislocations may be the dominant aging mechanism.

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Optimization of current spreading metal layer for GaN/InGaN-based light emitting diodes

Cited by 43 publications

References 13 publications

Effects of Current Spreading in GaN-based Light-emitting Diodes Using ITO Spreading Pad

Effects of Current Spreading in GaN-based Light-emitting Diodes Using ITO Spreading Pad

Au-Doped Indium Tin Oxide Ohmic Contacts to p-Type GaN

Study on the stability of the high‐brightness white LED

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