Anisotropic optical properties of a homoepitaxial (Zn, Mg)O/ZnO quantum well grown on a-plane ZnO substrate

The optical properties of homoepitaxial non-polar (Zn,Mg)O/ZnO single quantum wells (QWs) grown by molecular beam epitaxy on a-plane (11-20) ZnO substrates are investigated by using reflectance and continuous wave photoluminescence spectroscopies. The reflectivity and CW-PL spectra measured at low temperature reveal strong in-plane optical anisotropies and clear reflectance structures. The signatures of confined excitons analogous to C-exciton and (A, B)-excitons in bulk ZnO, are detected using light polarized respectively along the c-axis and perpendicular to this axis. Temperature dependence of CW-PL has been investigated in the two polarizations. For electric field of the light perpendicular to the c-axis the total intensity of the PL lines decreases by about an order of magnitude when the temperature increases from 8 K to room temperature. At low temperature a line associated to an excitonic complex dominates the PL spectrum. When the temperature increases the intensity of this line decreases as the intensity of the line associated to the free exciton increases. In the other polarization for temperature above 100 K a new line appears in the spectrum. Its intensity increases with temperature. This feature is associated to the c-like free exciton. The degree of polarization of these lines is independent of temperature. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)