title: Analysis of Schottky Contact Formation in Coplanar Au/ZnO/Al Nanogap Radio Frequency Diodes Processed from Solution at Low Temperature.
abstract: Much work has been carried out in recent years in fabricating and studying the Schottky contact formed between various metals and the n-type wide bandgap semiconductor zinc oxide (ZnO). In spite of significant progress, reliable formation of such technologically interesting contacts remains a challenge. Here, we report on solution-processed ZnO Schottky diodes based on a coplanar Al/ZnO/Au nanogap architecture and study the nature of the rectifying contact formed at the ZnO/Au interface. Resultant diodes exhibit excellent operating characteristics, including low-operating voltages (±2.5 V) and exceptionally high current rectification ratios of >10(6) that can be independently tuned via scaling of the nanogap's width. The barrier height for electron injection responsible for the rectifying behavior is studied using current-voltage-temperature and capacitance-voltage measurements (C-V) yielding values in the range of 0.54-0.89 eV. C-V measurements also show that electron traps present at the Au/ZnO interface appear to become less significant at higher frequencies, hence making the diodes particularly attractive for high-frequency applications. Finally, an alternative method for calculating the Richardson constant is presented yielding a value of 38.9 A cm(-2) K(-2), which is close to the theoretically predicted value of 32 A cm(-2) K(-2). The implications of the obtained results for the use of these coplanar Schottky diodes in radio frequency applications is discussed.
authors.affiliation: Department of Physics and Centre for Plastic Electronics Blackett Laboratory, Imperial College London , London SW7 2AZ, United Kingdom.
authors.forename: James
authors.initials: J
authors.lastname: Semple
authors.affiliation: Department of Physics and Centre for Plastic Electronics Blackett Laboratory, Imperial College London , London SW7 2AZ, United Kingdom.
authors.forename: Stephan
authors.initials: S
authors.lastname: Rossbauer
authors.affiliation: Department of Physics and Centre for Plastic Electronics Blackett Laboratory, Imperial College London , London SW7 2AZ, United Kingdom.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Anthopoulos
keywords: RFID; Richardson constant; ZnO; adhesion lithography; planar Schottky diode; radio frequency diode; solution processing