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We report on the formation of highly reliable Ti/Al-based Ohmic contacts to N-polar n-GaN for vertical light-emitting diodes via laser-annealing. All as-deposited samples are Ohmic with specific contact resistances of 1.1 - 4.3 × 10-4 Ω cm2. After annealing at 250°C, unlike the untreated sample, the laser-annealed samples remain Ohmic with specific contact resistances of 2.6- 3.9 × 10-4 Ω cm2. The laser-annealed samples remain electrically stable up to 60 min at 300°C. Laser-annealing causes the formation of interfacial TiN/β -AlN phases with rock salt structure. Based on X-ray photoemission spectroscopy and scanning transmission electron microscopy results, possible Ohmic mechanisms are described.
Date of Publication: Dec.1, 2011