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Temperature Dependence of Multimode Operations in Gallium Nitride / Aluminum Nitride (GaN/AlN) Nanomechanical Resonators Wen Sui Authors: Wen Sui, Xu-Qian Zheng, Philip Feng Faculty Mentor: Philip Feng, PhD College: College of Engineering Department: Electrical and Computer Engineering |
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AbstractGallium nitride has been commonly used in light-emitting diodes (LEDs) and high-frequency and high-power electronics, thanks to its wide bandgap (Eg = 3.4 eV), p-type doping capability, high mobility, and high thermal conductivity. In addition, spurred by GaN’s high elastic modulus and piezoelectricity, the material has also draw great attention for microelectromechanical system (MEMS) applications. GaN thin-film bulk acoustic resonator (FBAR) and MEMS resonator with integrated high electron mobility transistor (HEMT) body have been demonstrated. However, the polar crystalline structure of GaN together with the lattice mismatch between GaN and the underlying substrate may induce localized strain, affecting the performance of GaN-based MEMS and electronic devices. One way to analyze this effect is to monitor the mechanical response of such structure upon temperature change. Here, we report on the experimental characterization of the temperature coefficient of frequency (TCf) in the GaN/AlN heterostructure doubly-clamped string resonators using an ultrasensitive laser interferometry system. We measure a fundamental mode resonance frequency at ~1.8 MHz with a Q of ~10,000. By tracking the resonance frequency at varying temperatures (-10 ºC to 105 ºC), we obtain TCfs of -316 ppm/K for the fundamental resonance mode and -294 ppm/K for the second resonance mode. Further, analyze of the device will be conducted by comparing the results from multiphysics simulation with measurement to resolve the interlayer strain distribution in the GaN/AlN composite.
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