We report on a high sensitivity of GaN–AlN–GaN semiconductor–insulator–semiconductor structures grown on sapphire to an applied strain. The measured static gauge factor (GF) is almost twice as large as the GF forn-type SiC films. We link the observed magnitude and sign of the gauge factor to the crystalline structure of the GaN and AlN films and to their piezoelectric constants. We show that even higher sensitivity can be achieved if the material and interface quality is improved. ©1997 American Institute of Physics.