PhD Thesis

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« Modelling and test of integrated mechanical sensors based on AlGaN/GaN heterostructures for harsh environments ».

Author: S. Vittoz
Advisor: L. Rufer
President of jury: S. Basrour
thesis reviewer(s): I. Dufour, J.-C. De Jaeger,
These de Doctorat Université de Grenoble
Speciality: Micro et Nano Electronique
Defense: December 13 2011
ISBN: 978-2-84813-181-8


Some industrial areas as oil, automotive and aerospace industries, require electromechanical systems working in harsh environments. An elegant solution is to use III–V materials alloys having semiconductor, piezoelectric and pyroelectric properties. These materials, particularly nitrides such as GaN or AlN, enable design of advanced devices suitable for harsh environment. By using free-standing structure coupled with sensing HEMT transistors that are stable at high temperatures, it is possible to obtain mechanical sensors suitable for harsh environments. This PhD thesis focuses on a cantilever-based strain sensor and a drumskin-based pressure sensor. Analytical models of both sensors have been developed and establish the feasibility of the sensing principle as well as its response linearity. The characterization tests of fabricated prototypes validate the possibility of measuring external mechanical load with both sensors. The linearity of the response has also been confirmed by experimental measurements. The experimental sensitivity is smaller than the theoretical one due to several parasitic effects not included in the model such as parasitic resistance and variable piezoresisitive effects.

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