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°C to +50°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.