Frequency Mixing with HfO₂-Based Ferroelectric Transistors.

Area of Science:

• Radiofrequency electronics
• Solid-state physics
• Materials science

Background:

• Second harmonic generation (SHG) and frequency mixing are crucial for radiofrequency (RF) applications.
• Ferroelectric field-effect transistors (FeFETs) utilizing hafnium oxide (HfO2) exhibit symmetric transfer curves, showing potential for SHG.
• Optimizing FeFETs for RF signal processing requires understanding the influence of material properties on device performance.

Purpose of the Study:

• To investigate the impact of ferroelectric layer thickness and silicon substrate doping on FeFET symmetry and SHG performance.
• To demonstrate frequency mixing (sum and difference generation) using a single FeFET.
• To explore the electrical control of spectral components in RF signals via ferroelectric switching.

Main Methods:

• Fabrication of FeFETs with varying HfO2 thickness and silicon doping levels.
• Characterization of device symmetry and second harmonic generation (SHG) efficiency.
• Experimental demonstration of sum and difference frequency generation using the FeFETs.

Main Results:

• FeFET symmetry was found to be highly sensitive to ferroelectric thickness and substrate doping.
• SHG conversion gain and spectral purity were significantly improved (up to 96%) through precise tuning.
• Single FeFETs successfully generated both sum and difference frequencies, attributed to strong quadratic nonlinearities.

Conclusions:

• HfO2-based FeFETs offer a promising platform for efficient SHG and frequency mixing in RF applications.
• Precise control over material properties and ferroelectric switching enables enhanced device performance.
• This work paves the way for novel, electrically controlled frequency manipulation using simple ferroelectric devices.