Study of piezoelectric effect in GaN thin films using a modified Michelson interferometer

A single-beam interferometer has been set up to study the piezoelectric response of III-V semiconductors. Small displacements, induced by a driving voltage at a fixed frequency, can be detected and give a direct measurement of the piezoelectric coefficient. The system calibration is checked using a quartz specimen, and the measured d/sub 11/ value is 2.34 pm/V. Measurements on GaN films grown by chemical vapour deposition are also reported. Errors arising from non-uniform film deposition and from substrate bending are discussed.