Model and Simulation of GaN-Based Pressure Sensors for High Temperature Applications-Part II: Sensor Design and Simulation

In this part, design and optimization guidelines are presented for an Aluminium Gallium Nitride (AlGaN)/GaN-on-Silicon (Si) High Electron Mobility Transistor (HEMT)-based pressure sensor, for high temperature applications. The work presented here is based on the compact model developed and presented in Part I. The nature of the developed model allows not only the simulation of the sensor behavior for the case of a single HEMT sensor, but also for the case of a Wheatstone bridge configuration. Both configurations are analyzed in terms of temperature compensation, pressure sensitivity, and mechanical failure limits. Based on the presented analysis, we propose an optimized design of a temperature compensated pressure sensor for a pressure operation range between -10 bar and 10 bar, and for temperatures up to 500 degrees C. The optimization includes the epitaxial design, HEMT placement on the sensor membrane, membrane thickness and geometry, and the optimal biasing points for a maximum sensitivity. Strong temperature compensation can be achieved with less than 0.3 % sensitivity deviation up to 500 degrees C. The maximum sensitivity of 2.6 (mV)/(barV) can be achieved by applying a gate voltage near the pinch-off voltage of the device or as proposed here, by recessing the barrier locally under the gate. In addition, design guidelines for other pressure ranges are given. The approach taken here can be applied to a different epitaxial design with different barrier composition and substrate using the same compact model.