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 (HfO
₂
) 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 HfO
₂
spacer between ZnO and silver contact yields the highest effective Schottky barrier height (~0.7 eV) accompanied by a pronounced rectification ratio (reaching 7 × 10
²
at ±2.5 V) of the examined planar structure.