Investigation of a Reliable Ohmic Contact to n-Type ZnO Thin Films Prepared by Sol–Gel Method

摘要

In this letter, we investigated Ti (20 nm)/Al (30 nm)/Au (60 nm) metallic contacts to Al-doped ZnO thin films prepared by the sol–gel method. In order to measure specific contact resistance, circular transfer length method structures were patterned on the samples by a lithography process. The samples were annealed at the different temperatures and electrical characterization (–) was performed. The annealing process was optimized to produce ohmic contacts with the lowest specific contact resistance. The results showed that the sample annealed at 350 °C had the lowest specific contact resistance of . Surface and cross section energy dispersive X-ray analysis was used to determine the distribution of different elements during the annealing process. The results indicated effective inter-diffusion of Al and Ti as well as out-diffusion of oxygen, resulting in an increase in the n-type carrier concentration close to the surface of the ZnO. Scanning electron microscopy and atomic force microscopy analysis were used to determine the effect of annealing on the surface morphology.