Strain Relaxation, Defects and Cathodoluminescence of m-Plane ZnO and Zn0.8Mg0.2O Epilayers Grown on γ-LiAlO2 Substrate

Abstract

The strain relaxation, defects and luminescence properties of nonpolar (100) ZnO and Zn0.8Mg0.2O epilayers grown on γ-LiAlO2 (100) substrates by chemical vapor deposition were investigated by X-ray diffraction, transmission electron microscopy and cathodoluminescence. The X-ray rocking curves of (100) reflection possessed a low FWHM value of 504 and 216 arcsec, respectively, for ZnO and Zn0.8Mg0.2O. Reciprocal space maps indicated that the misfit strain in the [110] direction has been relaxed and resulted in misfit dislocations in high density at the interface with b = , which has been confirmed by TEM. The misfit strain along [0001] was, however, retained. Basal stacking faults, threading dislocations and inversion domains were observed in the ZnO epilayer with densities of 105 cm−1, 109 cm−2 and 104 cm−1, respectively. Moreover, only basal stacking faults and threading dislocations were found in Zn0.8Mg0.2O, having densities of about one order of magnitude lower than those of ZnO. The Zn0.8Mg0.2O epilayers exhibited a near band-edge emission at 3.5 eV whose intensity is about 15 times stronger than that of ZnO at 3.3 eV. Monochromatic cathodoluminescence images acquired at the peak energy revealed that the basal stacking faults showed low emission intensities at room temperature.