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.
Fay, M. W., Han, Y., Brown, P. D., Harrison, I., Hilton, K., Munday, A., …Martin, T. (2008). Structural and electrical characterization of AuPtAlTi ohmic contacts to AlGaN/GaN with varying annealing temperature and Al content. Journal of Applied Physics, 103(7), doi:10.1063/1.2890978