Metal/nonpolar m-plane ZnO contacts with and without thin Al2O3 interlayer deposited by atomic layer deposition

Using the temperature dependent current–voltage (I–V) measurements, the electrical properties of Au/nonpolar m -plane ZnO Schottky diodes with an Al 2 O 3 interlayer prepared by atomic layer deposition (ALD) was investigated. With an Al 2 O 3 interlayer, it was found to have higher barrier heights and higher rectifying ratio. Modified Richardson plots produced effective Richardson constants of 30.0 and 37.6 Acm −2 K −2 for the samples with and without Al 2 O 3 interlayer, respectively, which are similar to the theoretical value of 32.0 Acm − 2 K − 2 for n-ZnO. Scanning transmission electron microscope (STEM) results showed that the oxygen-contained layer on ZnO surface degraded the film quality of subsequently deposited Al 2 O 3 layer. In addition, the inter-diffusion of Au and Al atoms into ZnO subsurface region also modulated the electrical properties of Au/ZnO contacts.