Electrical and Optical Properties of High Mobility W-doped In2O3 Thin Films

Abstract

Transparent conducting oxides (TCO) have been widely used for opto-electronic devices such as light emitting diodes, photo-detectors, touch panels, flat panel displays, and solar cells. Low resistivity, high mobility, and good transparency are the prime requirements for these devices. There is an increasing interest in TCO with high mobility to decrease their electrical resistivity without a significant decrease in the optical transparency. Highly conducting and transparent tungsten doped indium oxide thin films were deposited on quartz substrate by ablating the sintered In₂O₃ target containing WO₃ with a KrF excimer laser (λ = 248 nm and pulsed duration of 20 ns). The effect of growth temperature and oxygen pressure on structural, optical, and electrical properties has been studied. The transparency of the films largely depends on the growth temperature. The electrical properties are found to depend strongly on the growth temperature as well as on oxygen pressure. The temperature dependence resistivity measurement shows the transition from semiconductor to metallic behavior as the growth temperature increases from room temperature to 500 °C. The high mobility (up to 358 cm²V⁻¹s⁻¹), low resistivity (1.1 × 10⁻⁴ Ω.cm), and relatively high transmittance of ∼90 % have been observed on the optimized film grown at 500 °C and under oxygen pressure at 1 × 10⁻⁶ bar.