Improved Nanoscale Al-Doped ZnO with a ZnO Buffer Layer Fabricated by Nitrogen-Mediated Crystallization for Flexible Optoelectronic Devices

To achieve excellent semiconductor device performance, especially for low-temperature processing of semiconductors, the need to devise strategies to engineer the surface and interface and to develop characterization techniques to understand the cause-effect relationship of surface and interface of semiconductor devices remains to be a key issue. Here, we present a nucleation control method, termed nitrogen-mediated crystallization (NMC), to engineer the surface morphology of a ZnO buffer layer and analyze first- and second-degree statistical surfaces to reveal the morphological relationship between the buffer layer and the buffered AZO film. The surface parameter is generally understood as the surface roughness (roughness average or RMS roughness) or the surface height profile, and our experimental results suggest that the physical properties of the buffered AZO films are strongly influenced by the fractal geometry of the buffer layers and are insensitive to their surface roughness. We demonstrate that the NMC method promotes enhanced surface migration and effectively prevents the development of nonuniform fractal geometry in the ZnO buffer layer, enabling the stress relaxation in the buffered AZO films and mitigating the three-dimensional columnar growth. At a low thermally induced kinetic energy, a 90 nm thick AZO film with an ultralow resistivity of 4.4 × 10-4 ω·cm can be achieved, indicating its potential for the realization of high-efficiency flexible optoelectronic devices.