Scienza e Tecnologia
WPI-MANA Demonstrates New GaN MEMS Resonator Is Temperature-stable up to 600 K
The finding could result in faster 5G electronics devices thanks to better integration of GaN-based micro-electromechanical and nano-electromechanical systems (MEMS/NEMS) with the current semiconductor technology.
The GaN resonator, fabricated on a silicon substrate, had a low temperature coefficient of frequency (TCF) of several ppm/K (parts per million per degree Kelvin) and high-quality (Q) factors without degradation up to 600 K .
The millimeter-wave 5G system that is driving the much-anticipated "internet of things" requires increasing modulation complexity to improve data bandwidth. But conventional quartz oscillators are limited by their inability to integrate well with semiconductor electronics. Using MEMS/NEMS for reference oscillators is one way to achieve high resonance frequencies with less phase noise and high temperature stability.
Silicon-based MEMS resonators usually have a large negative TCF of around -30 ppm/K. Temperature compensation techniques, including geometry modification, impurity doping and multilayer structures, have been proposed to improve the TCF, but these degraded the system's Q factors.
The MANA team used elastic strain engineering, a technique to modulate the strain at the heterojunction of the resonator structure, which helped to store energy and thereby increase Q factors.
In contrast to conventional flexural modes, the internal thermal stress at high temperatures improved the TCF of the GaN MEMS resonator by over 10 times, without losing the high Q factor.
Group III nitrides have been excellent wide bandgap semiconductors for high-frequency electronics in the 5G era. The integration of such MEMS with electronics is therefore promising for IoT sensors and communications devices.
This research was carried out by Liwen Sang , Independent Scientist (WPI-MANA, National Institute for Materials Science), and her collaborators.
"Self-Temperature-Compensated GaN MEMS Resonators through Strain Engineering up to 600 K " L. Sang et al., 2020 IEEE International Electron Devices Meeting ( March 11 , 2021) https://doi.org/10.1109/IEDM13553.2020.9372065
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