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  • Received: Feb. 21, 2020

    Accepted: Jun. 18, 2020

    Posted: Jun. 18, 2020

    Published Online: Jul. 31, 2020

    The Author Email: Luca Sulmoni (

    DOI: 10.1364/PRJ.391075

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    Luca Sulmoni, Frank Mehnke, Anna Mogilatenko, Martin Guttmann, Tim Wernicke, Michael Kneissl. Electrical properties and microstructure formation of V/Al-based n-contacts on high Al mole fraction n-AlGaN layers[J]. Photonics Research, 2020, 8(8): 08001381

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Photonics Research, Vol. 8, Issue 8, 08001381 (2020)

Electrical properties and microstructure formation of V/Al-based n-contacts on high Al mole fraction n-AlGaN layers

Luca Sulmoni1,*, Frank Mehnke1, Anna Mogilatenko2,3, Martin Guttmann1, Tim Wernicke1, and Michael Kneissl1,2

Author Affiliations

  • 1Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin, Germany
  • 2Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, 12489 Berlin, Germany
  • 3Institut für Physik, Humboldt Universität zu Berlin, 12489 Berlin, Germany


The electrical and structural properties of V/Al-based n-contacts on nAlxGa1-xN with an Al mole fraction x ranging from x=0.75 to x=0.95 are investigated. Ohmic n-contacts are obtained up to x=0.75 with a contact resistivity of 5.7×10-4 Ω·cm2 whereas for higher Al mole fraction the IV characteristics are rectifying. Transmission electron microscopy reveals a thin crystalline AlN layer formed at the metal/semiconductor interface upon thermal annealing. Compositional analysis confirmed an Al enrichment at the interface. The interfacial nitride-based layer in n-contacts on nAl0.9Ga0.1N is partly amorphous and heavily contaminated by oxygen. The role and resulting limitations of Al in the metal stack for n-contacts on n-AlGaN with very high Al mole fraction are discussed. Finally, ultraviolet C (UVC) LEDs grown on nAl0.87Ga0.13N and emitting at 232 nm are fabricated with an operating voltage of 7.3 V and an emission power of 120 μW at 20 mA in cw operation.

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