High-Quality Aligned GaN/ZnO Nanowires Grown by Thermal Evaporation for UV Detector Application

Abstract

Gallium nitride (GaN) nanowires (NWs) were grown on Zinc oxide/silicon (ZnO/Si) (1 substrate(100) by thermal evaporation method. The magnetron sputtering technique was used to deposit ZnO thin film. High-density nanostructured GaN was formed as shown in the scanning electron microscopy image. X-ray diffraction showed that ZnO/Si and GaN films had a hexagonal wurtzite structure. Photoluminescence (PL) of ZnO/Si showed strong peak at 382.84 nm (3.23 eV),while PL of GaN/ZnO/Si NWs exhibited a strong band-edge emission at approximately 338.94 nm (3.65 eV), which belongs to GaN NWs. Broadening of the energy bandgap compared with the growth of GaN (3.45 eV) could have occurred because of nanocrystalline structure quantum confinement effects. Raman spectrum of ZnO/Si nanocrystalline thin films showed a band located at 579 cm−1 that can correspond to the A1(TO) mode. Furthermore, the Raman bands at approximately 520 cm−1 correspond to the first-order transverse optical (1TO) mode of the c-Si substrate. For GaN/ZnO/Si NWs, Raman-active optical phonons are assigned to 568 cm−1 because of E2 (high). The I–V characteristics of GaN/ZnO/Si indicated the excellent ultraviolet photoresponse.