Threshold voltage shift by controlling Ga in solution processed Si–In–Zn–O thin film transistors

The threshold voltage change of solution processed gallium–silicon–indium–zinc oxide (GSIZO) thin film transistors (TFTs) annealed at 200 °C has been investigated depending on gallium ratio. GSIZO thin films were formed with various gallium ratios from 0.01 to 1 M ratio. The 30 nm-thick GSIZO film exhibited optimized electrical characteristics, such as field effect mobility (μFE) of 2.2 × 10− 2 cm2/V·s, subthreshold swing (S.S) of 0.11 V/dec, and on/off current ratio (Ion/off) of above 105. The variation of gallium metal cation has an effect on the threshold voltage (Vth) and the field effect mobility (μFE). The Vth was shifted toward positive direction from − 5.2 to − 0.4 V as increasing gallium ratio, and μFE was decreased from 2.2 × 10− 2 to 5 × 10− 3 cm2/V s. These results indicated that gallium was acted as carrier suppressor by degenerating oxygen vacancy. The electrical property of GSIZO TFTs has been analyzed as a function of the gallium ratio in SIZO system, and it clearly showed that variation of gallium contents could change on the performance of TFTs.