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HL: Fachverband Halbleiterphysik

HL 25: Poster: Nitrides

HL 25.8: Poster

Montag, 20. März 2017, 15:00–19:00, P2-OG2

Ohmic V-based contacts on n-Al0:8Ga0:2N for deep UV LEDs — •Luca Sulmoni¹, Martin Guttmann¹, Johannes Enslin¹, Christian Kuhn¹, Frank Mehnke¹, Tim Wernicke¹, and Michael Kneissl^1,2 — ¹Technische Universität Berlin, Institut für Festkörperphysik — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin

Minimizing the contact resistance on both p- and n-layers in deep ultraviolet (UV) light emitting diodes (LEDs) is essential for improving the efficiency of these devices suffering from the high operating voltages and resistive heating. Ohmic contacts to n-Al_xGa_1−xN are challenging especially for high AlN mole fractions mainly due to the low electron affinity. Standard metal schemes such as Ti/Al/Ti/Au can form ohmic n-contacts only up to about 40% AlN mole fraction. In this study, we investigated the influence of vanadium as first-layer metal in a four-metal electrode V/Al/Ni/Au.

We evaluated the contact characteristics under various annealing conditions. The V/Al/Ni/Au contacts on n-Al_0.8Ga_0.2N annealed at 800^∘C under N₂ atmosphere exhibit ohmic characteristics with contact resistivities as low as 8·10⁻⁵ Ω cm² at a current density of 0.1 kA/cm². In contrast, Ti/Al/Ti/Au contacts form rectifying Schottky barriers of about 6 V. We finally demonstrate the fabrication of UVC LEDs emitting at 265 nm using both electrodes. A significant reduction of the operating voltage compared to the standard Ti/Al/Ti/Au electrodes was observed with V_op 11 V instead of 21 V at a current of 50 mA.