Optical and electrical properties of transparent conducting B-doped ZnO thin films prepared by various deposition methods

Abstract

B-doped ZnO (BZO) thin films were prepared with various thicknesses up to about 500 nm on glass substrates at 200 °C by dc or rf magnetron sputtering deposition, pulsed laser deposition (PLD), and vacuum arc plasma evaporation (VAPE) methods. Resistivities of 4–6 × 10−4 Ω cm were obtained in BZO thin films prepared with a B content [B/(B + Zn) atomic ratio] around 1 at. % by PLD and VAPE methods: Hall mobilities above 40 cm2/Vs and carrier concentrations on the order of 1020 cm−3. All 500-nm-thick-BZO thin films prepared with a resistivity on the order of 10−3–10−4 Ω cm exhibited an averaged transmittance above 80% in the wavelength range of 400–1100 nm. The resistivity in BZO thin films prepared with a thickness below about 500 nm was found to increase over time with exposure to various high humidity environments. In heat-resistance tests, the resistivity stability of BZO thin films was found to be nearly equal to that of Ga-doped ZnO thin films, so these films were judged suitable for use as a transparent electrode for thin-film solar cells.