Piezoelectric Al1-xScxN thin films: A semiconductor compatible solution for mechanical energy harvesting and sensors

The transverse piezoelectric coefficient e(31,f) of Al1-xScxN thin films was investigated as a function of composition. It increased nearly 50% from x = 0 to x = 0.17. As the increase of the dielectric constant was only moderate, these films are very suitable for energy harvesting, giving a 60% higher transformation yield (x = 0.17) as compared to pure AlN. A higher doping might even lead to a 100% augmentation. The thickness strain response (d(33,f)) was found to increase proportionally to the ionic part of the dielectric constant. The e-type coefficients (stress response), however, did not augment so much as the structure becomes softer. As a result, the transverse voltage/strain response (h(31,f)-coefficient) was raised only slightly with Sc doping. The low dielectric loss obtained at all compositions suggests also the use of Al1-xScxN thin films in sensors. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4800231]