Ti/Al Multilayer Ohmic Contact To n-GaN On Sapphire

Ohmic contacts are essential to GaN-based high power devices. Ti/Al layer is the basic building block to depositohmic contacts on n-GaN used for making such devices. Ti (10 nm)/Al (40 nm)/Ti (30 nm)/Al (20 nm) /Ti(20 nm) multi-layer metal scheme was chosento induce Al3Ti formation close to the contact-semiconductor interface and TiAl close to the contact surface. This Ti/Al multilayer has been grown on n-GaN by physical vapor deposition and annealed at 600 °C in nitrogen ambient for 30 s that resulted in contact resistivity of 0.011 0.cm2. This study is focused on eliminating the need of capping and blocking layers, reducing total contact thickness and hence reduce fabrication cost. TiAl3and TiAlalloy formation after annealing was confirmed by GI-XRD while SEM confirmed thermal stability of the contact.