We investigate the dependence on Mg content of the lattice parameters and the surface morphology of nonpolar [formula] Zn1−xMgxO (x≤0.55) grown by molecular beam epitaxy. The anisotropy of the lattice parameters gives r

We investigate the dependence on Mg content of the lattice parameters and the surface morphology of nonpolar [formula] Zn_1-xMg_xO (x≤0.55) grown by molecular beam epitaxy. The anisotropy of the lattice parameters gives rise to an unusual in-plane strain state in the ZnO QWs: tensile strain along [1<OVERLINE>1</OVERLINE>00] and compressive strain along [0001]. For a Zn_0.6Mg_0.4O barrier, the strain in a ZnO QW reaches -1.3% along [0001] and +0.3% along [1<OVERLINE>1</OVERLINE>00]. This induces a strong blueshift of the excitonic transitions, in addition to the confinement effects, which we observe in photoluminescence excitation experiments. [ABSTRACT FROM AUTHOR]