Ohmic contact properties of non-polar a-plane GaN films on r-plane sapphire substrates

摘要

The properties of Ti/Al/Ni/Au Ohmic contacts on n-type a-plane GaN epitaxial layers directly grown on r-plane sapphire substrates are reported. The minimum specific contact resistance of ～10~(-5) Ω cm ~2 was achieved after annealing at 650-700 °C. Ohmic contact properties were measured using transmission line method patterns oriented in both the m- and c-axis directions of a-plane GaN. The sheet resistance of a-plane GaN along the c-axis was two times higher than that along the m-axis, which shows significant electric anisotropy in the two orientations.