High transparency low resistance oxidized Ni/Au–ZnO contacts to p-GaN for high performance LED applications

Jung, Sung-Pyo; Lin, Chien‐Hung; Chan, Hon Man; Fan, Zhiyong; Jiang, Lu; Lee, Henry P.

doi:10.1002/pssa.200405095

phys. stat. sol. (a)

2004

DOI: 10.1002/pssa.200405095

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High transparency low resistance oxidized Ni/Au–ZnO contacts to p-GaN for high performance LED applications

Sung-Pyo Jung¹,

Chien‐Hung Lin²,

Hon Man Chan³

et al.

Abstract: This paper presents high-transparency low-resistance contact on p-GaN using oxidized Ni/AuZnO : Al 2 O 3 (2 wt%) for high-performance GaN-based light-emitting diodes (LEDs) applications. It is shown that oxidized Ni/Au -ZnO contact to p-GaN yields an operating voltage of around 4.7 V at 20 mA compared to 4.1 V of a reference oxidized Ni/Au(5 nm/5 nm) -Ni/Au(20 nm/120 nm) sample without the ZnO : Al 2 O 3 (2 wt%) layer. Enhancement of transmittance of about 60% at the wavelength of 450 nm over a conventional N … Show more

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Cited by 3 publications

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“…Jung et al revealed that significant increase in resistivity could be observed in the O 2 ambient annealed AZO films. 8 The increase could be attributed to the reduction of oxygen vacancies ͑V O ͒. 8 The increased resistivity can enhance the current crowding effect when utilized as p-type contacts of GaN-based LEDs.…”

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confidence: 99%

“…8 The increase could be attributed to the reduction of oxygen vacancies ͑V O ͒. 8 The increased resistivity can enhance the current crowding effect when utilized as p-type contacts of GaN-based LEDs. In this study, the AZO and Ni/AZO schemes were deposited on p-GaN followed by nitrogen ambient thermal annealing to form high-transparency and lowresistivity ohmic contacts.…”

mentioning

confidence: 99%

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Effects of Thermal Annealing on Al-Doped ZnO Films Deposited on p-Type Gallium Nitride

Tun

Sheu

Lee

et al. 2006

J. Electrochem. Soc.

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In this study, Al-doped ZnO ͑AZO͒ and Ni/AZO films were deposited on p-type GaN films followed by thermal annealing to form ohmic contacts. After thermal annealing, the resistivities of AZO films reduced from 5 ϫ 10 −3 to 4-6 ϫ 10 −4 ⍀ cm. Both as-deposited AZO and Ni/AZO contacts on p-GaN displayed a non-ohmic characteristic. Only the 800°C-annealed Ni/AZO contacts exhibited a linear current-voltage characteristic, showing a specific contact resistance of around 1.2 ϫ 10 −2 ⍀ cm 2 . After undergoing the annealing in nitrogen ambience, the light transmittance of the Ni/AZO films increased from 70% to higher than 90% in the visible range. These results revealed that the Ni/AZO contact can serve as a suitable transparent current spreading layer for the fabrication of GaN-based light-emitting devices.Reliable and transparent contact layers are essential elements used in the development of high-brightness, GaN-based light emitting diodes ͑LEDs͒. Hitherto, bilayer metallization, such as Ni/Au, 1 and Pt/Au, 2 have been the subject of extensive research and investigation. In order to enhance the light-extraction efficiency, the Ni/Au thin film serving as anode electrode is commonly annealed in oxygen-containing ambient to form a low-resistivity and semitransparent ohmic contact to p-GaN. 3 In general, the transmittance of such semitransparent contacts is only around 60-75% in the visible region and lower than 60% in the ultraviolet ͑UV͒ region. Thus, in order to further improve the light-extraction efficiency of LEDs, high-transparency and low-resistivity top contact layer, such as indium tin oxide ͑ITO͒, 4,5 is necessary. However, the ITO films in direct contact with the p-GaN layer, showed a non-ohmic currentvoltage ͑I-V͒ behavior even after thermal annealing. 5 In order to eliminate this behavior, a Ni layer was inserted between the ITO film and p-GaN layer to improve electrical properties. 6 Aluminumdoped zinc oxide ͑AZO͒ is a well-known wide-bandgap material. It has good potential for utilization in transparent contact layers. Song et al. 7 reported that Ni/AZO bilayer contacts deposited onto p-type GaN followed by thermal annealing in ambient air could possess linear I-V characteristics, but the light transmittance was only about 76% with wavelengths in the range of 400-550 nm. Jung et al. revealed that significant increase in resistivity could be observed in the O 2 ambient annealed AZO films. 8 The increase could be attributed to the reduction of oxygen vacancies ͑V O ͒. 8 The increased resistivity can enhance the current crowding effect when utilized as p-type contacts of GaN-based LEDs. In this study, the AZO and Ni/AZO schemes were deposited on p-GaN followed by nitrogen ambient thermal annealing to form high-transparency and lowresistivity ohmic contacts. ExperimentalThe wafers used in this study were all grown on c-face sapphire ͑0001͒ substrates by metallorganic vapor phase epitaxy ͑MOVPE͒. The Mg-doped GaN films with a thickness of 1 m were grown on a 2-m-thick GaN template followed by a N 2 -ambient th...

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confidence: 99%

mentioning

confidence: 99%

Effects of Thermal Annealing on Al-Doped ZnO Films Deposited on p-Type Gallium Nitride

Tun

Sheu

Lee

et al. 2006

J. Electrochem. Soc.

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show abstract

Effects on electrical and optical properties of InGaN/GaN MQWs light-emitting diodes using Ni/ITO transparent p-contacts on p-GaN

Singh

Chauhan

Mathew

et al. 2019

J Opt

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Electrical and optical properties of InGaN/GaN MQWs light-emitting diodes with Ni/Au/ITO transparent p-contacts

et al. 2019

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High transparency low resistance oxidized Ni/Au–ZnO contacts to p-GaN for high performance LED applications

Cited by 3 publications

References 10 publications

Effects of Thermal Annealing on Al-Doped ZnO Films Deposited on p-Type Gallium Nitride

Effects of Thermal Annealing on Al-Doped ZnO Films Deposited on p-Type Gallium Nitride

Effects on electrical and optical properties of InGaN/GaN MQWs light-emitting diodes using Ni/ITO transparent p-contacts on p-GaN

Electrical and optical properties of InGaN/GaN MQWs light-emitting diodes with Ni/Au/ITO transparent p-contacts

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