Boron nitride (BN) films are grown on sapphire substrates by plasma-assisted chemical vapor deposition. BN films are doped with sulfur (S). The electrical resistivity of the S-doped BN film is reduced to 103 Ω cm, while the electrical resistivity of the undoped BN film is 1011 Ω cm. It is demonstrated that the negative electron affinity appears on the BN surface. Insertion of a GaN layer between the BN film and sapphire leads to a tight adhesion of the BN film. Cathode and anode electrons are formed on the BN film and the sapphire substrate, respectively, by evaporating Ti and Au. An emission current of 1 μA is obtained at an electric-field strength of 16 V/μm for the planar field emitter. An emission current density as high as 0.1 A/cm2 is detected. It is expected that the planar field emitters can be operated at several tens V with a decreased cathode–anode spacing and that the present field emitter structure is applicable to a field-emission panel display. © 1999 American Vacuum Society.