Study on the GaN/AlGaN Piezotronic Effect Applied in Pressure Sensors

Abstract

The GaN piezotronic effect is known as the coupling of its semiconductor and piezoelectric properties. In this work, with FEM simulation we study this effect applied in the piezoresistive, capacitive, and piezoelectric pressure sensors. The piezoresistive and capacitive sensing elements which are directly integrated in a single 2 μ m thick microcantilever show a gauge factor of 251 and 1600, respectively. The piezoelectric sensing element of 2 μ m GaN film anchored at the end of a thick suspended cantilever shows significant output voltage depending on the donor doping concentration in GaN. The capacitive sensing element of a graded AlGaN/GaN heterostructure with linear change of Al mole fraction which is anchored on the thick suspended cantilever shows a gauge factor of 122. This sensing mechanism can be explained that the pressure applied on the cantilever changes the distribution of space piezoelectric polarization charge and further the width of depletion region in the heterostructure.

High‐Electron‐Mobility Transistor‐Inspired Freestanding AlGaN/GaN/AlN Optical Waveguide for High‐Pressure Sensing Applications

“…[ 3 ] The reported GaN HEMT‐based pressure sensor will operate either on charge mode or capacitance, [ 5 ] and electrical quantities like voltage or current are used for measurements. [ 7 ] In addition, the approach to acquire these measurements can be categorized in three forms, namely, a bulk device approach, a device integrated on bulk cantilevers, [ 10 ] and membrane structures. [ 11 ] Out of the three approaches, the membrane‐based pressure sensor works much more efficiently due to the induced spontaneous polarization, suggesting that AlGaN/GaN‐based HEMT is a perfect choice for robust pressure sensing in electrical domain.…”