Magnitudes of strain in ZnO epitaxial layers grown on sapphire(0001) substr
ates under various growth conditions were experimentally determined by x-ra
y diffraction. We discuss the strain-induced energy shift on the exciton re
sonances, the results of which were analyzed theoretically using the Hamilt
onian for the valence bands under in-plain biaxial strain. Comparative stud
ies with GaN evidenced the advantages of ZnO in terms of sensitivity of the
strain-induced energy shift and of piezoelectric effect in heterostructure
s. (C) 2001 American Institute of Physics.