【Device Papers】Universal Ohmic contacts to β-Ga₂O₃ using interfacial dipoles of ultra-thin MgF₂ layer and related defect passivation

      Researchers from the Indian Institute of Technology Ropar have published a dissertation titled "Universal Ohmic contacts to β-Ga₂O₃ using interfacial dipoles of ultra-thin MgF₂ layer and related defect passivation" in Applied Physics Letters.

Abstract

      We report on the role of MgF₂ as an interfacial buffer layer to achieve universal Ohmic contact on polycrystalline β-Ga₂O₃ thin film. Polycrystalline Ga₂O₃ thin films were deposited using RF magnetron sputtering, followed by the growth of MgF₂ through a modified approach within the same technique, enabling enhanced fluorination via trapped fluorine species. Three representative metals like Al (low work function ≈4.0 eV), and Ni, Au (high work functions ≈5.0 eV) were investigated to assess contact behavior. All three metals formed Schottky junctions with Ga₂O₃ in direct contact while insertion of an MgF₂ interlayer resulted in a clear transition to Ohmic conduction. Interface analysis using x-ray photoelectron spectroscopy (XPS) and Kelvin probe force microscopy (KPFM) revealed that fluorine incorporation passivates oxygen vacancies, reducing Fermi-level pinning, while Ga–F interfacial dipoles induce downward band bending. These combined effects effectively lower the Schottky barrier height enabling universal Ohmic contacts across metals with different work functions.

DOI：

https://doi.org/10.1063/5.0308375