Amorphous boron-indium-zinc-oxide active channel layers for thin-film transistor fabrication

We investigate thin-film transistor (TFT) fabrication, using a novel amorphous boron-indium-zinc-oxide (a-BIZO) thin-film as an active channel layer and a radio-frequency sputtering technique. The structural, surface, and optical properties of the a-BIZO thin-film were studied. X-ray diffraction (XRD) patterns and high-resolution transmission electron microscopy (HR-TEM) analysis confirmed the amorphous nature of the a-BIZO thin-film. Atomic force microscopy revealed a smooth a-BIZO thin-film surface with a uniform and root mean square roughness of 0.45 nm. The transparency of a-BIZO thin-films was shown to be more than 80% in the wavelength range between 400 and 800 nm, which confirmed a good transparency. The a-BIZO TFT post-annealed at 250 °C under nitrogen atmospheric conditions showed a saturation field-effect mobility of 9.6 cm² V^-1 s^-1, a threshold voltage of 5.3 V, and a subthreshold swing of 0.77 V per dec with an I_ON/I_OFF current ratio of 2.5 × 10⁷. The small amount of boron dopant acts as a strong carrier suppressor via the formation of oxygen vacancies in the a-IZO matrix.