Operating Temperature Trends in Amorphous In-Ga-Zn-O Thin-Film Transistors

The electrical performance as a function of operating temperature of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) is assessed by measuring drain current versus gate voltage [log(I-D)-V-GS] transfer curves at temperatures from -50 degrees C to + 50 degrees C. These bottom-gate staggered a-IGZO TFTs are fabricated using thermal silicon dioxide as the gate insulator. An almost rigid log(I-D)-V-GS transfer curve shift to lower (more negative) turn-on voltage (V-ON) with increasing temperature is observed. The extent of the V-ON operating temperature dependence of a TFT appears to be correlated to its trap density. A lower trap density gives rise to less V-ON operating temperature dependence. Although log(I-D)-V-GS transfer curves are observed to shift almost rigidly with temperature, a more detailed temperature-dependence assessment indicates that the shift is not exactly rigid. The mobility is found to increase slightly with increasing operating temperature. This trend is attributed to enhanced detrapping at a higher operating temperature.