Characteristics of Gallium-Doped Zinc Oxide Thin-Film Transistors Fabricated at Room Temperature Using Radio Frequency Magnetron Sputtering Method

摘要

In this paper, we present bottom-gate-type Ga-doped zinc oxide (GZO) thin-film transistors (TFTs) using a certain conventional SiO_2 gate insulator by applying a radio-frequency (RF) magnetron sputtering method at room temperature. A low gate leakage current was achieved using this conventional SiO_2 gate insulator instead of new gate oxide materials. The root mean square (RMS) value of the GZO film surface was found to be 1.65 nm, and the transmittance was higher than 75% in the visible region. The GZO TFTs operated in a depletion mode with a threshold voltage of —3.4V. A mobility of 0.023 cm~2/(V-s), an on/off ratio of 2 ×10~3, and a gate voltage swing of 3.3V/decade were obtained. We successfully demonstrated that the TFT of depletion-mode type can be fabricated using a GZO film that has good surface uniformity, transparency, and electrical characteristics.