Abstract
Transparent and electrical conducting p-type off-stoichiometric copper–chromium oxide thin films were used to build p-Cu0.66Cr1.33O2/n-ZnO heterojunctions. The junctions were fabricated in a novel and simple five step process including metal organic chemical vapour deposition, atomic layer deposition, chemical wet etching, and optical lithography. One last step of thermal annealing, with varying temperatures of 650 and 700 °C, is added in order to tune the electrical properties of delafossite and consequently the electrical features of p–n junctions. This work was developed to address the lack of transparent and industrially scalable rectifying p–n junctions that can open multiple application paths in transparent electronics. A competitive ideality factor η of 6.6 and a transmittance in the visible range of 50% were achieved. An understanding of the electronic response of junctions is presented herein as well as a deepening comprehension of the physical properties of materials, with the bands alignment and the Fermi level tuning.
Highlights
In the recent years, wide bandgap semiconductors have been investigated in order to build a transparent p–n junction
The fabrication of transparent diodes based on zinc oxide (ZnO) and Cu0.66Cr1.33O2, started with the deposition of Cu0.66Cr1.33O2 on sapphire substrate at 450 °C followed by ZnO deposited at 150 °C
Sapphire was chosen as a substrate due to its high temperature stability being adequate for wide temperature range studies
Summary
Wide bandgap semiconductors have been investigated in order to build a transparent p–n junction. Simple transparent p–n junctions can derive into photodetectors and photovoltaic cells and can open paths to more complex device as transparent transistors [2]. From this perspective, transparent conductive oxides (TCOs) are a special kind of materials that combine high electrical conductivity, interesting carrier mobility and large optical bandgap [3, 4]. Despite that its p-type conductivity was reported (under non-equilibrium conditions) [5], the problem of dopants asymmetry inducing the lack of reliability of the p-type layer impedes an adequate utilization of ZnO homo-junctions. The best electrical performances, combining high ION/IOFF ratio and ideality factor closer to 1 were reported by Grundmann
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