Enhancement of UV emission and optical bandgap of ZnO nanowires via doping and post-growth annealing

Zinc oxide (ZnO) nanowires (NWs) are gaining importance in optoelectronics because of their excellent electrical and optical properties. However, defects in the NW structure leads to suppression of the near-band-edge (NBE) ultraviolet (UV) emission, limiting their full potential for applications in optoelectronic devices. In this work, we present enhancement in NBE emission and bandgap modulation in ZnO NWs hydrothermally grown on sputtered Al-ZnO (AZO) films. Al dopant incorporation and post-synthesis thermal annealing are found to increase the NBE emission. Compared to Al-doping, the post-growth annealing produces a more significant enhancement in the NBE emission and a substantial increase of 34.5 meV in the optical bandgap, along with suppression of defect-related deep level emissions caused by oxygen vacancies and interstitials. This further improves the applicability of the ZnO NWs in stable, room temperature emission devices.