Al/Au ohmic contact to n-ZnO by dc sputtering

We deposited Al (50 nm)/Au (250 nm) layers on n-ZnO in order to produce low-resistance ohmic contacts by using a dc sputtering method. The samples were annealed at various temperatures for 1 min in N2 ambient. The electrical and the structural properties of the Al/Au contact to n-ZnO were investigated. According to the current–voltage measurements, both the as-deposited and annealed samples showed an ohmic behavior. The specific contact resistance of the sample annealed at 200 °C was 1.4 × 10−4 Ωcm2. Further increasing the temperature above 400 °C led to an increase in the specific contact resistance. The Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) measurements were used to characterize the nature of the interfacial layer between the Al/Au and ZnO layers. Possible explanation is given to describe the dependence of the annealing temperature on the electrical properties of Al/Au contact to n-ZnO.