Tuning the properties of ALD-ZnO-based rectifying structures by thin dielectric film insertion – Modeling and experimental studies

Abstract

This paper is devoted to the electrophysical diagnostics of the ZnO-based rectifying structures in which the semiconducting oxide layer has been obtained by the low-temperature (80 °C ≤ T ≤ 130 °C) Atomic Layer Deposition (ALD) process. For the growth of examined diodes an organic compound (diethylzinc, DEZn) was used as a zinc precursor. As an oxygen source either deionized (in case of Schottky rectifiers as well as for n-type part of homojunction) or ammonia water (for the p-type layer of homojunction) was applied. In order to improve the basic electrical parameters of these structures (with a particular interest in the rectification (ION/IOFF) ratio) a solution based on inserting the thin dielectric layer (HfO2 or Al2O3) either below the Ag Schottky contact or between the homodiode parts, respectively, has been tested. Through comparing the electrical properties of Ag/HfO2/ZnO/ITO Schottky diodes and ZnO homojunctions as well as modeling their room-temperature current–voltage (I–V) characteristics according to the differential approach it has been proven that the optimal interlayer thickness allowing to achieve the ION/IOFF parameter as high as 104–105 for approximately ± 2 V polarization voltage range is about 2.5–5-nm. Additionally, involving the theoretical studies, the dominant carrier transport mechanisms were identified to be the monopolar injection, tunneling/trapping phenomena occurring in the dielectric layer and bimolecular recombination. The achieved results predestine the examined structures to be applied in the modern electronic devices, where stable in time and good quality diodes are required.