Au-Free Multi-Layer Ti/Al Ohmic Contacts for AlGaN/GaN HEMTs

This paper studies Au-free, multi-layer Ohmic metal (Til AIITil AIITil AI/Ni/TiN 7.5/30/7.5/30/7.5/30/60/60 nm) stacking on the AIGaN/AIN/GaN heterostructure using low annealing temperature. The research indicates that an etching depth of 30 nm yields the most outstanding results when annealed at 800°C for 45 seconds. The low annealing temperature combined with the multi-layer ohmic metal stacking results in improved surface morphology, which is significant for AIGaNI AIN/GaN high electron mobility transistors (HEMTs). Additionally, the annealing temperature and time were optimized by the second experiment conducted. Multiple annealing treatments were performed to enhance the performance of Ohmic contacts without damaging the surface morphology. Under the annealing condition of800 °C, the contact resistance (Rc) reached 1.9 g.mm. Electrical property testing shows that the multi-layer Ohmic metal stacking with 30 nm etching depth proposed significantly outperform traditional Au-free Ohmic contacts under Til AI/Ni/TiN conditions.