Novel structural Ti/Al-based ohmic contacts on AlGaN/GaN heterostructures

To improve the performances of ohmic contacts for GaN devices, a novel multilayer Ti/Al-based metal scheme (Ti/Al/Ti/Al/Ti/Al/Ti/Al/Ni/Au) on undoped AlGaN/GaN heterostructures was employed. A contact with ?c (specific contact resistance) of 8.74E-07 ?·cm2, Rc of 0.22 ?·mm was demonstrated. Ohmic contacts with the novel metal structure were measured with I-V, SEM, HRTEM to show their properties. The results showed that ohmic contacts with novel structures have better surface morphology and proposed thermal stability than those using conventional Ti/Al/Ni/Au metal scheme, therefore ohmic contacts with novel structures should be better candidates for high power and high frequency GaN devices.