Bilayer Cr/Au contacts on n-GaN

Cr/Au (40/65 nm) metal layers have been deposited by thermal evaporation onto n-GaN epitaxial layers grown by metal-organic chemical-vapour deposition (MOCVD) on a sapphire substrate. The samples have been annealed at 400, 700 and 900 degrees C for 10 min in vacuum. Techniques of TEM, EDS, HRTEM, FESEM, XRD and I V characteristics have been used to characterize the micro-, and nanostructure, morphology, composition and electrical properties of the contacts before and after annealing. A binary phase of Cr3Ga4 and Au7Ga2 were identified at the interface of the n-GaN/Cr/Au contacts after annealing in vacuum at 700 and 900 degrees C. Current-voltage characterizations showed that the as-deposited and annealed Cr/Au contacts are rectifying up to 600 degrees C. After heat treatment in vacuum at 700 degrees C and 900 degrees C the Cr/Au contacts were linear. (C) 2011 Elsevier Ltd. All rights reserved.