Piezoelectric Tantalum Aluminum Nitride Films for Vibrational Micro Energy Harvesters

This paper reports the first attempt to apply highly piezoelectric Ta-doped AlN thin films for vibration-driven micro energy harvesters. Ta
_x
Al
_1-x
N (x = 0.068) films were grown on Pt/Ti/Si substrates and applied to microfabricate energy harvesters. The Ta-AlN films exhibit a highly c-axis crystal orientation and good electrical properties with low leakage current density of 0.2×10
^-6
A/cm
²
and low loss tangent of 0.02. Our prototype of the Ta-AlN based micro energy harvesters shows the normalized power density (NPD) of 13.7 mW.g
^-2
.cm
^-3
. This result was an approximately 6-fold increase compared to the best of the published pure AlN harvesters and outperformed the PZT-based ones. Also, our first attempt is approaching to the best-published performance of the higher co-dopant concentration (MgHf)
_0.11
Al
_0.89
N and Sc
_0.43
Al
_0.57
N.