Electrical Transport Properties Through Nanoscale and Large-Area Contacts of ZnO/Si Diodes

Abstract

A thorough understanding of the electrical transport behavior of large-area and nano-scale contact devices employing thin film homo- or hetero-junctions is critical to designing and fabricating high-performance optoelectronic devices. We investigate and discuss the electrical transport properties of ZnO diodes measured on macroscopic and nano-scale contacts based on current understanding of the field. The ZnO thin film based macroscopic and nano-scale diodes are the Au/ZnO/Si and conductive atomic force microscopy tip/ZnO/Si structures, respectively. The four large-area contact diodes exhibited different electrical properties such as ideality factor, turnon voltage and breakdown voltage, whereas the nano-scale contact diodes exhibited similar electrical property but different from the four large-area contact diodes. The electrical transport across the nanoscale contact junctions is believed to be dominated by tunneling; whereas in large-area contact diodes, it is predominant either by thermionic emission or tunneling depending on the doping type and dopant concentration of the Si substrates. These results provide an experimental demonstration and are expected to yield insights that are necessary for designing practical, high-performance nanophotonic devices based on ZnO thin films or nanostructures. Keywords: Semiconductor heterojunctions, Zinc compounds, Electrical transport, Thermionic emission, Tunneling, Nanoscale contact, Atomic force microscopy (AFM)