Hierarchical ZnGa2O4 and Cr doped Zn1 - xMnxGa2O4 nanostructures for room temperature light-emitting devices

Branched, hierarchically grown ZnGa2O4 and Zn-1 (-) xMnxGa2O4 (0.1 < x < 0.21) micro- and nanostructures have been fabricated by a thermal evaporation method. Comparison of both materials shows that the presence of Mn favours the formation of the branched morphology, with oriented nanowires of high crystalline quality. The origin of the growth of these nanostructures is discussed. Raman peaks are observed to broaden and shift as a function of Mn content in the alloy. Cathodoluminescence analysis shows that ZnGa2O4 structures emit the characteristic defect-related UV-blue band and Zn1 - xMnxGa2O4 nanowires show efficient green emission due to intraionic Mn2+ transitions. Zn1 - xMnxGa2O4 structures have been doped with Cr3+ during thermal treatments in presence of Cr. This leads to structures with additional red emission related to Cr3+. The excitation conditions allow selection of the dominant luminescence band. Photocurrent measurements have also been carried out in ZMGO structures, showing the characteristic intraionic Mn2+ transitions.