Non-Surface-Treated Au/ZnO Schottky Diodes Using Pre-Annealed Hydrothermal or Sol-Gel Seed Layer

Abstract

Nonsurface-treated zinc oxide (ZnO) Schottky diodes were fabricated on a Si substrate using one of two different seed layers, prepared by either the sol-gel or hydrothermal method. Then, ZnO film was grown on a seed layer by the hydrothermal method, and Au/ZnO Schottky diodes were fabricated to study the effects of different seed layers on the electric behavior. Observations show that the Schottky diodes grown on a hydrothermal seed layer exhibit very good rectifying behavior with a rectification ratio as large as 8000 at a bias voltage of ±2 V. In contrast, an ohmic behavior is observed in the Schottky diodes with sol-gel seed layer. Capacitance-voltage measurements demonstrate that the Schottky diodes grown on the hydrothermal seed layer have a Schottky barrier height of 0.77 eV as a result of Zn vacancies. However, a surface downward band bending is obtained in the ZnO grown on the sol-gel seed layer. The downward band bending renders a high carrier concentration on the ZnO surface, which is caused by the oxygen vacancies. Atomic ratio of Zn/O was investigated using Xray photoelectron spectroscopy and carrier transport mechanism was studied by current-voltage measurement.

Effects of Sn and Zn Seed Layers on the Electrical Characteristics of Pd/ZnO Thin-Film Schottky Diodes Grown on n-Si Substrates

“…The linear I∼V relation, for V < 0.15 for all the three Pd/ZnO Schottky diodes shows ohmic behavior of the device commonly attributed to the tunneling of charge carriers between the states at the interfaces [5]. For V > 0.15 V, the diodes nearly follow I ∼ exp (V) relation possibly due to the recombination tunneling mechanism [5].…”

“…The major difficulty in achieving a good SC on ZnO thin films is associated with the large density of intrinsic defects (especially oxygen vacancies) on the ZnO film's surface which may provide a leakage path to the device current thereby degrading the rectifier behaviour of ZnO Schottky diodes [4]. The effect of surface defects on the ZnO film's surface can be eliminated by using a very thin seed layer of a suitable material including ZnO [5], [6], Zn [7], Al 2 O 3 [8] on the surface of substrates on which ZnO films are required to be grown. The seed layers can reduce the lattice mismatching between the substrates and ZnO material thereby improving the structural, optical, and electrical characteristics of the ZnO films.…”

“…The seed layers can reduce the lattice mismatching between the substrates and ZnO material thereby improving the structural, optical, and electrical characteristics of the ZnO films. Hwang et al [5] reported Au on ZnO thin film grown by Hydrothermal (HT) method on p-Si substrates Manuscript with one of two seed layers fabricated by either HT or Sol-gel (SG) methods. While SG derived ZnO seed layer showed an ohmic nature of Au/ZnO contact, the HT method based seed layer resulted in the Schottky nature of Au/ZnO contacts a rectifying ratio of ∼8000.…”

“…While SG derived ZnO seed layer showed an ohmic nature of Au/ZnO contact, the HT method based seed layer resulted in the Schottky nature of Au/ZnO contacts a rectifying ratio of ∼8000. However, besides the works of Hwang et al [5] no significant work has been reported on the ZnO thin film based Schottky diodes grown on the seed layer coated substrates. In this view, we report possibly for the first time, the effects of Sn and Zn seed layers on the electrical characteristics of Pd/ZnO thin film Schottky diodes grown on seed-layer coated n-Si substrates by thermal evaporation method.…”

Various Techniques to Optimize the Quality of Schottky Contacts on ZnO Thin Films: A Short Review

“…There are few reports present in the literature on ZnO Schottky diode using buffer layers. Hwang et al [20] reported the Au/ZnO Schottky diode using pre-annealed seed layer. The seed layer was deposited by two methods.…”