Nonpolar short-period ZnO/MgO superlattices: Radiative excitons analysis

The basic structural and detailed analysis of the optical properties of homoepitaxially grown ZnO/MgO super lattices (SLs) on a-oriented ZnO substrates, containing 30 periods of layers, was described. We found using Rutherford backscattering spectroscopy that the wurtzite coordination collapses in the SLs with 3 nm MgO thick barriers. This novel information allows taking this value as the limit for the maximum MgO barrier thickness in such structures. The observed luminescence and the performed calculations of excitonic transitions suggest that such a high energy barrier of MgO allows treating the ZnO layers in these SLs as separate, non-interacting quantum wells. Cross-sectional SEM-CL line scans revealed MgO layer thickness-dependent biaxial strains built up in the QWs structures.

Automated summary

The study described the optical properties of homoepitaxially grown ZnO/MgO superlattices on a-oriented ZnO substrates and found that the wurtzite coordination collapses in the SLs with 3 nm MgO thick barriers. The high energy barrier of MgO in such structures allows treating the ZnO layers as separate quantum wells.