Low-Resistance Ohmic Contacts to AlGaN/GaN Heterostructure Using Si/Ti/Al/Cu/Au Multilayer Metal Scheme

A Si/Ti/Al/Cu/Au metallization scheme has been developed to achieve a low specific contact resistivity to a n-AlGaN/GaN heterostructure. A specific contact resistivity as low as 3.8 ×10-5 Ωcm2 was obtained after annealing at 800°C for 30 s. The interfacial reaction between the Si/Ti/Al/Cu/Au layers and the AlGaN was investigated by secondary-ion mass spectroscopy and transmission electron microscopy. An Al–Ti–Si–N intermetallic phase layer was observed at the interface. The ohmic contact formation is found to be related to Si diffusion and the formation of the Al–Ti–Si–N intermetallic phase layer.