Regensburg 2019 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 2: Nitrides: Devices

HL 2.13: Talk

Monday, April 1, 2019, 12:45–13:00, H31

Low resistance V/Al/Ni/Au n-contacts on n−Al_0.9Ga_0.1N for UVC LEDs — •Verena Montag¹, Luca Sulmoni¹, Frank Mehnke¹, Tim Wernicke¹, and Michael Kneissl^1,2 — ¹Technische Universität Berlin, Institute of Solid State Physics — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin

Deep UV LEDs emitting below 230nm require high aluminum n−Al_0.9Ga_0.1N current spreading layers. However, the n-contacts show poor performance as the current-voltage characteristics is not ohmic and high operating voltages are needed even for moderate current densities. This is partly due to the materials lower electron affinity and to the higher activation energies of the Si-donor as the aluminum content in the n-AlGaN layers increases. In this study, the thicknesses of the vanadium and aluminum layers in V/Al/Ni/Au-based n-contacts were varied in order to improve both voltage and contact resistivity. In addition, rapid thermal annealing of the n-contacts was investigated for a wide range of temperatures under N₂ ambient. We were able to achieve contact resistivities of 3.3·10⁻³ Ω cm² and voltages as low as 2.6V at a current density of 0.1kA/cm². Finally, we fabricated UVC LEDs emitting at 229nm with an output power of 10µW and a voltage of 9.8V measured on wafer for a dc current at 20mA.