Low-resistance, highly transparent, and thermally stable Ti/ITO Ohmic contacts to n-GaN

Abstract

Indium tin oxide (ITO) contacts to n-GaN have been optimized to achieve the minimal contact resistance and high optical transparency. It was found that evaporation-deposited ITO on n-GaN exhibited leaky Schottky characteristics even with predeposition plasma treatment and postdeposition annealing. The addition of a thin intermediate Ti (3–20nm thick) significantly improved the electrical characteristics, yet did not compromise the transparency of the ITO contacts. A thermally stable Ti/ITO Ohmic contact to n+-GaN, with a low specific contact resistance of 4.2×10−6Ωcm2 and a high transmittance ∼86% at 450nm, was obtained after 600°C annealing.