TiN/Al Ohmic contacts to N-face n -type GaN for high-performance vertical light-emitting diodes

We report on the electrical properties of TiN(30 nm)/Al(200 nm) Ohmic contacts to N-face n -type GaN for high-performance vertical light-emitting diodes and compare them with those of Ti(30 nm)/Al(200 nm) contacts. Both the as-deposited samples show Ohmic behaviors with contact resistivity of (6.0-7.2) × 10^-4 ∑ cm². However, annealing the samples at 300 °C causes the degradation of their electrical properties. Furthermore, unlike the TiN/Al contacts, the Ti/Al contacts suffer from aging degradation when exposed to air. Based on the x-ray photoemission spectroscopy and secondary ion mass spectrometry results, Ohmic formation and degradation mechanisms are briefly described and discussed.