AlGaN/GaN heterostructure based 3-dimensional force sensors

Tactile sensing is an essential physical-electrical gateway in sensing technology. Creating such sensors is a complex challenge if the goal is to reproduce human-like sensation. Classical MEMS tactile sensor solutions in typical environmental conditions exist few types, but harsh conditions such as space technology or high-temperature range are not solved yet. One proposed material complex is the GaN/AlGaN system. In this study, we present an AlGaN/GaN MEMS force sensor for external force and load direction sensing in the mN range. The demonstrated sensor showed a sensitivity of 100 mV/N/V, which is an order of magnitude higher than the Si-based sensor with the same geometry. The sensing mechanism is based on the interface discontinuity between compound alloy layers, where two-dimensional electron gas (2DEG) is created and in which the carrier concentration can be linearly modulated by the internal crystal stress. The location of the sensing element was optimized by FEM simulation. The maximum load force of the samples varies with direction, which information allows the sensor to be used without fatigue and to obtain safety an electrical response signal under different external tensions. In addition to the advantage of this design for harsh environments, it is also possible to monolithically integrate active elements adjacent to the sensor for local acquisition and processing of the measured signal.