High velocity SAW using aluminum nitride film on unpolished nucleation side of free-standing CVD diamond

Abstract

High performances surface acoustic wave (SAW) filters based on aluminium nitride (AlN)/diamond layered structure have been fabricated. The C-axis oriented aluminum nitride films with various thicknesses were sputtered on unpolished nucleation side of free-standing polycrystalline chemical vapor deposition (CVD) diamond obtained by silicon substrate etching. Experimental results show that high order modes as well as Rayleigh waves are excited. Experimental results are in good agreement with the theoretical dispersion curves determined by software simulation with Green's function formalism. We demonstrate that high phase velocity first mode wave (so-called Sezawa wave) with high electromechanical coupling coefficient are obtained on AlN/diamond structure. This structure also has a low temperature coefficient of frequency (TCF), and preliminary results suggest that a zero TCF could be expected.

SAW Characteristics of AlN/SiO2/3C-SiC Layered Structure With Embedded Electrodes

“…The temperature behavior of the layered structure can be calculated by pre-stressed analysis study using the thermo-mechanical coupling modeling based on COMSOL, which is validated by comparison of the calculated TCF of AlN based layered structure with experimental ones reported by Elmazria et al [14]. For a given temperature (T), the shift in resonant frequency (Δf) can be computed by incorporating the linear thermal expansion coefficients and temperature coefficients of elasticity into the model.…”

High precision pressure sensors based on SAW devices in the GHz range

“…Nevertheless, the results obtained for the devices processed on AIN/free-standing NCD are the highest obtained so far on nanocrystalline diamond [32]. Moreover, the achieved frequency is the highest obtained among other freestanding NCD structures [22][23][24]. In addition, these results are in agreement with the ones obtained before [28], and confirm that the AIN/free-standing NCD structure is an alternative to the more expensive polished MCD for the processing of high performance and high frequency SAW devices.…”

“…Some works have proposed alternative methods in order to overcome these disadvantages. These consist of using the smooth unpolished nucleation side of freestanding diamond layers [22][23][24]. This solution requires the whole Si substrate to be sacrificially etched.…”

Nature of optical transitions involving cation vacancies and complexes in AlN and AlGaN

“…Together with previous results, a more complete picture for the optical transitions involving cation vacancy related deep centers in AlGaN alloy system has been constructed. Al-rich AlGaN and AlN have been the subject of intense research effort during the last decade due to their applications in deep ultraviolet (DUV) photonics, 1-5 surface acoustic wave (SAW) devices, 6,7 and field emitters. 8 The superior physical and chemical properties of AlN, such as ultra-wide direct bandgap, 9,10 high melting point, 11 high thermal conductivity, 12 mechanical strength, and radiation hardness, miscibility with GaN in the entire alloy region, make it technologically important.…”