G. Vanko, J. Dzuba, I. Rýger, M. Vallo, T. Lalinský
Institute of Electrical Engineering, Slovakia
pp. 290 - 293
Keywords: gallium nitride, piezoelectricity, pressure sensor, HEMT
The III Nitrides (III-N), especially gallium nitride (GaN) and its compounds, are very attractive for pressure and strain sensing thanks to their excellent piezoelectric properties. The AlGaN/GaN heterostructure offers high mechanical and chemical stability, operation at high temperatures and possibility to fabricate the high electron mobility transistors (HEMTs). Previously, we proposed the circular HEMT (C HEMT) as a sensing element integrated on thick substrate based cantilever structure . To improve the sensor sensitivity and mutual compatibility, new diaphragm based sensors with integrated C HEMTs as a sensing device were designed and fabricated. The AlGaN/GaN heterostructures were grown by metal oxide chemical vapor deposition (MOCVD). The sensor metallization was fabricated using the front side processing of C HEMT (electron beam and standard evaporation techniques) and suspended diaphragms were produced by deep reactive ion etching (DRIE) process . The residual stress was considered as the key parameter of such MEMS pressure sensor. These findings contributed to the complex electrical or mechanical modeling what resulted in better optimization of the sensor.  G. Vanko et al., Sens. Actuat. A-Phys 172 (2011) 98-102.  T. Lalinský et al., Microelectronic Eng. 98 (2012) 578-581.