We report on the formation of thermally stable ohmic contacts on n-type ZnO:Al (nd = 2 × 1018 cm-3) using a Re/Ti/Au metallization scheme. It is shown that the as-deposited Re/Ti/Au contact is ohmic with a contact resistivity of 2.1 × 10-4 Ω cm2. The electrical characteristics of the samples are further improved upon annealing, namely, the sample produces a specific contact resistance of 1.7 × 10-7 Ω cm2 when annealed at 700°C for 1 min in a nitrogen ambient. Atomic force microscopy results show that the surface of the samples is reasonably smooth with a root-mean-square roughness of 6.0 nm when annealed at 700°C. The carrier transport mechanism is described using the relationship between temperature and specific contact resistance. Based on X-ray diffraction and X-ray photoemission spectroscopy results, the ohmic mechanism for the annealed samples is also described and discussed.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry