Dresden 2017 – wissenschaftliches Programm
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 Kneissl1,2 — 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-AlxGa1−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-Al0.8Ga0.2N 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 Vop 11 V instead of 21 V at a current of 50 mA.