Annealed Ti/Cr/Al contacts on n-GaN

In this study we report on the micro-, And nanostructural, morphological and electrical properties of Ti(20 nm)/Cr(120 nm)/Al(50 nm) contacts to n-GaN by electron microscopy, X-ray diffraction and I-V measurements. Tested contacts were annealed at the temperature of 400, 700 and 900 degrees C for 10 min in vacuum. It was found that Cr appeared in the top part of the GaN epitaxial layer at 700 degrees C. High resolution electron microscopy (HREM) revealed Ti2AlN MAX phase as well as Al2O3 phase at the interface of n-GaN/Ti/Cr/Al contact at 900 degrees C. X-ray diffraction examinations showed that new Ti2AlN MAX phase formed and Cr3GaN as well as CrN phases developed at 900 degrees C. I-V characterizations exhibited that while the as-deposited and annealed Ti/Cr/Al contacts are rectifying up to 700 degrees C the diffusion of Cr into the epi GaN layer led to ohmic behaviour at 700 degrees C. (c) 2013 Elsevier Ltd. All rights reserved.