Strain-enhanced high Q-factor GaN micro-electromechanical resonator

Area of Science:

• Materials Science
• Mechanical Engineering
• Nanotechnology

Background:

• Gallium nitride (GaN) micro-electromechanical systems (MEMS) are crucial for various sensing applications.
• Achieving high quality factors (Q) and resonant frequencies (f) simultaneously in GaN MEMS is challenging.
• Existing GaN MEMS often exhibit lower Q-factors, limiting their performance.

Purpose of the Study:

• To develop a highly sensitive GaN MEMS resonator with a record-high quality factor.
• To investigate the effect of strain engineering on the resonant frequency and Q-factor of GaN-on-Si structures.
• To demonstrate the application of the developed GaN MEMS as a high-resolution mass sensor.

Main Methods:

• Fabrication of double-clamped GaN beam bridges on a silicon substrate.
• Implementation of strain engineering by controlling tensile stress up to 640 MPa.
• Utilizing lattice mismatch between GaN and Si to introduce tensile stress.
• Characterization of resonant frequency (f) and quality factor (Q).
• Demonstration as a mass sensor by detecting microdroplet evaporation.

Main Results:

• Achieved a record quality factor (Q) exceeding 10^5 at a resonant frequency (f) of 911 kHz.
• Increased the resonant frequency of GaN beam bridges from 139 kHz to 911 kHz through tensile stress.
• Obtained an ultra-high Q-factor, two orders of magnitude higher than previously reported GaN MEMS.
• Demonstrated a mass sensor resolution of 10^-12 g/s.

Conclusions:

• Strain engineering in GaN-on-Si structures is an effective method to enhance the f × Q product of MEMS resonators.
• High tensile stress significantly reduces energy dissipation, leading to ultra-high Q-factors.
• The developed GaN MEMS resonator shows great potential for highly sensitive mass sensing applications.