Modal Analysis of Gallium Nitride Membrane for Pressure Sensing Device

Abstract

A circular high electron mobility transistor (C-HEMT) prepared on the AlGaN/GaN membrane surface has been investigated and its potential for pressure sensing has been already demonstrated. The key issue in the design process of such heterostructure based MEMS sensors is the stress engineering. This way we can scale the sensor performance, measured pressure range and sensitivity. Especially, the knowledge of the exact value of the residual stress in membranes (caused by deposition process) helps us to optimize the sensing devices. In this work, the residual stress determination method in gallium nitride circular shaped membrane is reported. It is shown that resonant frequency method using Laser Doppler Vibrometry (LDV) for membrane vibration measurement seems to be an appropriate technique to determine the residual stress in micro-scale membranes. Circularly shaped AlGaN/GaN micro-membranes are excited by acoustic short time pulse. The decay oscillating motion of the membrane is recorded by oscilloscope. By FFT spectral analysis of the signals the resonance frequencies are obtained. For the sample studied, the natural frequency mode resonance peak is used to define the residual stress level. To verify the observed stress in investigated membranes, prestressed modal analysis in finite element method (FEM) code ANSYS is performed. The stress extracted from the measured frequency is taken as an initial stress state of the modelled membrane. Experimentally obtained shock spectra are compared with that computed by FEM simulation.

Ultra-Thin Wood-Based Acoustic Diaphragms Fabricated via an Environmentally Friendly Strategy

“…The tensile strength test was used to evaluate the mechanical properties of the wood and wood diaphragm with different species. 18 Tensile tests of the manufactured samples confirmed significant material properties could be obtained through pressing densification after delignification and sulfonation treatments while maintaining the hierarchical integrity of the wood, as shown by representative stress−strain curves presented in Figure 4a. Figure 4b compares the stress− strain curves of the UWD with other widely used polymers.…”

“…The acoustic performance was tested according to the previous research. 18 A speaker sent out the frequency range of 1.5−50 kHz white noise to the wood acoustic diaphragm which was fixed in a circular mold. Moreover, the laser vibrometer (PLV-202, MTC, China) emitted a laser beam to the wood acoustic diaphragm to achieve high-precision vibration displacement measurement (test range 1 mm, low pass filter 22 kHz).…”

Analysis of Vibration of Roadheader Rotary Table Based on Finite Element Method and Data from Underground Coalmine

“…The degree of freedom (DOF) of the underside node and pins of the rotary table is constrained. The finite element model after the constraint is then analyzed, and the exported modal neutral file is imported into ADAMS [18]. Based on the MNF document and flexible body port, the vibration model is built using ADAMS, and the finite element and vibration models are developed, as shown in Figure 6.…”