Liquid-Metal Fabrication of Ultrathin Gallium Oxynitride Layers with Tunable Stoichiometry

The synthesis of nanometer-thick (approximate to 3 nm) gallium oxynitride (GaOxNy) layers with a variable stoichiometry is reported. The approach primarily exploits the liquid metal chemistry (LMC) technique and promises easier integration of 2D materials onto photonic devices compared to traditional top-down and bottom-up methods. The fabrication follows a two-step process, involving first liquid metal-based printing of a nanometer-thick layer of gallium oxide (Ga2O3), followed a plasma-enhanced nitridation reaction. Control over nitridation parameters (plasma power, exposure time) allows adjustment of the GaOxNy layer's composition, granting access to compounds with distinct optical properties (e.g., a 20% index variation), as demonstrated by ellipsometry and density functional theory (DFT) simulations. DFT provides a microscopic understanding of the effect of the bond polarization and crystallinity on the optical properties of GaOxNy compounds. These findings expand the knowledge of ultrathin GaOxNy alloys, which are poorly studied with respect to their gallium nitride (GaN) and Ga2O3 counterparts. They also represent an essential step toward integrating such 2D materials into photonic chips and offer new opportunities to improve the performance of hybrid optoelectronic devices. In this study, ultrathin gallium oxynitride films are synthesized with a composition adjusted between gallium oxide and gallium nitride. The process involves a cost-effective two-step approach, utilizing liquid metal-based squeeze printing followed by plasma-assisted nitridation. Extensive characterization provides insights into the composition and optical properties of the resulting nanometer-thick layers.image (c) 2023 WILEY-VCH GmbH