Low-Resistance Si/Ti/Al/Ni/Au Multilayer Ohmic Contact to Undoped AlGaN/GaN Heterostructures

A Si/Ti/Al/Ni/Au metallization scheme was investigated for the formation of very low ohmic contacts on undoped AlGaN/GaN heterostructures. The influences of the silicon layer thickness and the annealing temperature on the contact resistance were studied using linear transmission line model (TLM) patterns. A contact resistance of 0.23 Ω mm, corresponding to a specific contact resistance of Ω cm 2 , was achieved with a 30 Å thick silicon layer annealed at 800°C for 30 s.