Role of the Hafnium Dioxide Spacer in the ZnO-Based Planar Schottky Diodes Obtained by the Low-Temperature Atomic Layer Deposition Method: Investigations of Current-Voltage Characteristics

This paper reports on results of modeling of current-voltage characteristics of the Ag/ZnO/TiAu planar Schottky diodes containing interfacial layer of hafnium dioxide (HfO₂) with thickness ranging from 1.25 to 7.5 nm. It was found that forward characteristics can be described with thermionic emission theory. In this way, values of some relevant diodes´ parameters were determined, including the ideality factor and the effective Schottky barrier height. We found a satisfactory agreement of experimental and theoretical results for most diodes, with exception of the one with a 7.5-nm thick layer. It was found that a 2.5-nm thick HfO₂ spacer between ZnO and silver contact yields the highest effective Schottky barrier height (~0.7 eV) accompanied by a pronounced rectification ratio (reaching 7 × 10² at ±2.5 V) of the examined planar structure.