Structural and electrical characterization of AuPtAlTi Ohmic contacts to AlGaN∕GaN with varying annealing temperature and Al content

The effect of varying annealing temperature and Al layer thickness on the structural and electrical characteristics of AuPtAlTi∕AlGaN∕GaN Ohmic contact structures has been systematically investigated. The relationship between annealing temperature, Al content, interfacial microstructure, surface planarity, and contact resistance is examined. In particular, the presence of a detrimental low temperature Pt–Al reaction is identified. This is implicated in both the requirement for a higher Al:Ti ratio than is required for related AuPdAlTi contact schemes and through the degraded temperature dependent resistance behaviour of the annealed AuPtAlTi contacts.