Characterization of UHF Schottky diodes based on oxide semiconductors

Future societies will benefit from a constantly increasing degree of automation in all aspects of everyday life. The ultimate connectivity from machine to machine and from human to machine via wireless networks will become a reality under the wider notion of the Internet of Things (IoT). The key elements of IoT applications are a radio frequency (RF) reader/emitter in association with a RF identification (RFID) tag, the microelectronic component attached to an object, based on a single custom CMOS integrated circuit (which included a rectifier) and an antenna. While high frequency (HF) tags operating at 13.56 MHz are usually restricted to a read distance below 10 cm, ultra high frequency (UHF) devices are capable of operating over some meters that increase the sphere of device application. UHF rectifiers based on Schottky diode as a part of interfacing chain will be a cornerstone in interfacing of a mobile telephone, as one of the most popular device in everyday life, and printed functional objects. Amorphous metal oxide semiconductor materials such as ZnO, InZnO, SnO, InO2, InGaZnO are considered as the most suitable materials to realize such Schottky diodes.

One of the important problems in characterization of electronic component in the UHF range, especially based on new materials on flexible substrates, consist in the signal reflection and attenuation at contacting points in the circuit where the impedances of characterized component (e.g. Schottky diode) and measuring devices are not matched. The main cause of the signal reflection is a based on the oxide semiconductor device itself with unknown and frequency-dependent impedance, whereas the rest of the circuit (cables and probes) has an impedance of 50 Ω. The problem of impedance matching could be solved by development of matching circuit or measurement cell using classical approaches of circuit design. An application of resonant measurement methods allows definition of such electrical characteristics of the functional material as a dielectric constant and dielectric loss tangent in accordance to a resonant frequency and Q-factor of the system. Preliminary investigation of materials properties represents a fundamental approach to measuring process optimization and determination of measuring values ranges and system limitations.

As the first stage the low-frequency measurements will be performed by LCR-meter, and UHF measurements will be carried out by a vector spectrum analyzer with a frequency range up to 3 GHz as the second stage. These measurements will help to carry out the energy-harvesting properties of developed diode from mobile phones and more specifically, within the global system for mobile communication frequency bands currently used by all mobile networks (i.e. roughly at 850 MHz/1.9 GHz in America and 900 MHz/1.8 GHz in Europe and other parts of the globe).

To summarize, the project is devoted to the development and assembling of characterization system for the UHF Schottky diode based onto flexible substrate and its fundamental metal oxide materials.

Participants:

  • Empa - Swiss Federal Laboratories for Materials Science and Technology
  • National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”
    • Prof. Dmytro Tatarchuk
    • Dr. Yurii Didenko