N-polar n-type Ohmic Contact of GaN-based LED on Si substrate

Ti/Al contacts have been deposited by electron beam Evaporation onto N-polar n-type surfaces of GaN-based vertical structure LED on Si substrate. The effect of AlN buffer layer on ohmic contact of these chips has been investigated through I-V characteristic. The results shown Ti/Al contacts prepared on N-polar n-type surface without AlN buffer layer became ohmic contact after annealing in the temperature range of 500-600 degrees C. The as-deposited Ti/Al contacts on N-polar n-type surface with AlN buffer layer shown ohmic behaviors with a specific contact resistivity of 2 x 10(-5) Omega cm(2) and maintained ohmic contact characteristics until anneal at 600 degrees C. Therefore, The exsiting of AlN buffer layer is the key to forming highthermal stability ohmic contact for GaN-based vertical structure LED on Si substrate.