Temperature Dependence of Intrinsic Channel Mobility in Indium-Gallium-Zinc-Oxide TFTs

This work reports on the development of a new TCAD material and device model for Indium-Gallium-Zinc-Oxide TFTs that accounts for operation from 150 K to room temperature, over applied gate and drain bias conditions up to 10 V. Specified defect state distributions include oxygen vacancy donors, conduction band-tail acceptor states, and acceptor-like interface traps. The presented model allows the TCAD simulation to account for the behavior of defect states according to defined energy distributions, thus properly regulating the amount of free channel charge. An intrinsic channel mobility defined as only a function of temperature was found to accurately represent extended state transport. The intrinsic channel mobility was 19 cm
²
/V•s at room temperature, with a reduction to 9 cm
²
/V•s at T = 150 K. The functional dependence reflects a thermally-activated diffusive mobility with a distinct activation energy E
_a
= 40 meV, that is shown to be independent of the Fermi level.