Characteristics of indium-tin-oxide Schottky contacts to ZnMgO/ZnO heterojunctions with band gap grading

Abstract

We report on electrical characteristics of indium-tin-oxide (ITO) Schottky contacts to transparent n-n isotype heterojunctions composed of a compositionally graded Zn1−xMgxO (g-ZnMgO) and ZnO films fabricated on ITO-coated glass substrates. The transparent ITO Schottky contacts to g-ZnMgO/ZnO heterostructures resulted in excellent diode characteristics with the rectification ratios as high as 104 at a bias voltage of ±3.0 V. The effective Schottky barrier heights were about 0.6 eV and could be tuned by modifying the electrical properties of g-ZnMgO layer. The formation of high barrier Schottky contacts was discussed in conjunction with a band gap grading and a highly resistive surface layer of g-ZnMgO.

Comparison of Aluminum Zinc Oxide and Indium Tin Oxide for Transparent Conductive Oxide layer in Cu(In,Ga)Se2Solar Cell

“…Therefore, the ITO film of this study is believed to be partially crystallized, so that the resistance of the film is varying laterally. For instance, S. Bowden et al [6] reported a simulation result on the exactly same phenomenon that I-V curve seems to have a very low shunt resistance when a very high resistance, for example 150 ohm, affects a small portion as much as 10% of the cell. This means that the effect is due solely to the lateral non-uniformity of sheet resistance of ITO.…”

Engineering Schottky Contacts in Open-Air Fabricated Heterojunction Solar Cells to Enable High Performance and Ohmic Charge Transport

“…It should follow that if electrons need to overcome a Schottky barrier in order to be injected from the Zn 0.8 Mg 0.2 O to the ITO, the current density–voltage ( J – V ) curve should display rectifying behavior. 25 Unexpectedly, this rectification is absent, with a linear J – V plot (Figure 2 b) exhibited. 26 A linear J – V curve in the presence of a Schottky barrier may be due to (i) the Zn 0.8 Mg 0.2 O Fermi level being pinned by surface states, leading to no band-bending, 26 , 27 (ii) the potential difference between Zn 0.8 Mg 0.2 O and ITO being screened as a result of surface dipoles introduced by localized surface states 27 or (iii) charge tunneling through the Schottky barrier, either directly or via trap states extending below the band-edge of the Zn 0.8 Mg 0.2 O.…”

A New Approach to the Fabrication of Memristive Neuromorphic Devices: Compositionally Graded Films

“…The rectifying characteristic of the device is attributed to the graded band gap of g -Al:ZnMgO, causing highly asymmetric Schottky barrier heights at the electrode contacts [ 29 ]. The current in the positive bias region increases rapidly above a voltage of ~3.5 V and I - V curves become quite asymmetric, resulting in the rectifying behavior.…”

“…Advances in thin film technology have enabled the fabrication of well-controlled graded band gap semiconductor systems [ 22 , 23 ]. Regarding oxide materials, deposition of epitaxial films with graded composition is possible when the constituent materials of the films are isomorphic [ 28 , 29 , 30 ]. During this experiment, g- Al:MgZnO films are deposited using AACVD, as shown schematically in Figure 1 .…”