Regensburg 2016 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 35: Poster I
HL 35.36: Poster
Tuesday, March 8, 2016, 15:00–19:00, Poster A
Ohmic Ti/Al/TiN Contacts to n-GaN Fabricated by Sputter Deposition — •Valentin Garbe1, Juliane Walter1, Wolfram Münchgesang1, Alexander Schmid2, Ronald Otto2, Thomas Behm1, Barbara Abendroth1, and Dirk C. Meyer1 — 1Institute of Experimental Physics, TU Bergakademie Freiberg, Leipziger Str. 23, 09599 Freiberg, Germany — 2Institute of Applied Physics, TU Bergakademie Freiberg, Leipziger Str. 23, 09599 Freiberg, Germany
The annealed Ti/Al/metal/Au contact metallization has emerged as the most used Ohmic contact to n-GaN. While the Ti/Al bilayer is crucial for contact formation, the metal/Au capping layer prevents oxidation and Ga and Al diffusion. However, Au degrades the contact resistance, as itself diffuses to the GaN interface. Here, we present the fabrication and characterization of an Au-free Ti/Al/TiN contact stack to n-GaN with TiN serving as the diffusion barrier. Sputter deposition and lift-off in combination with post deposition annealing at 850 ∘C for 300 s are used for contact formation. After annealing, contacts show Ohmic behavior to n-GaN and a resistivity of 1.60× 10−3 Ω cm2. To understand the contact formation on the microscopic scale, the contacts were characterized by current–voltage measurements, linear transmission line method, X-ray reflectivity, X-ray diffraction, and X-ray photoelectron spectroscopy. Results show diffusion of Ti, Al, N and Ga during annealing, formation of TiN at the GaN/Ti interface, as well as formation of cubic and hexagonal AlN. However, the TiN layer was stable during annealing and proved to be an effective diffusion barrier and prevented oxidation successfully.