Effects of Ta incorporation in Y_2O_3 gate dielectric of InGaZnO thin-film transistor

摘要

The effects of Ta incorporation in Y_2O_3 gate dielectric on the electrical characteristics of InGaZnO thin-film transistor are investigated. With an appropriate Ta content in the Y_2O_3 gate dielectric, the saturation mobility of the thin-film transistor can be significantly increased, about three times that of the control sample with Y_2O_3 gate dielectric. Accordingly, the sample with a Ta/Ta+Y ratio of 68.6% presents a high saturation mobility of 33.5 cm~2 V~(-1)s~(-1) low threshold voltage of 2.0 V, large on/off current ratio of 2.8 × 10~7, and suppressed hysteresis. This can be attributed to the fact that the Ta incorporation can suppress the hygroscopicity of Y_2O_3 and thus reduces the Y_2O_3/ InGaZnO interface roughness and also the traps atear the interface, as supported by atomic force microscopy and low-frequency noise measurement, respectively. However, excessive Ta incorporation in the Y_2O_3 gate dielectric leads to degradation in device performance because Ta-related defects are generated.