Modelling and optimisation of a sapphire/GaN-based diaphragm structure for pressure sensing in harsh environments

GaN is a potential sensor material for harsh environments due to its piezoelectric and mechanical properties. In this paper an 8mm diameter sensor structure is proposed based on a GaN/AlGaN/sapphire HEMT wafer. The discs will be glass-bonded to an alumina package, creating a `drumskin' type sensor that is sensitive to pressure changes. The electromechanical behaviour of the sensor is studied in an attempt to optimise the design of a pressure sensor (HEMT position and sapphire thickness) for operation in the range of 10-50 bar (5 MPa) and above 300°C.