  Thin film transistors, with channels composed of In-X-Zn oxides, IXZO, with X
dopants: Ga, Sb, Be, Mg, Ag, Ca, Al, Ni, and Cu, were fabricated and their I-V
characteristics were taken at selected temperatures in the 77K<T<300K range.
The low field mobility, mu, and the interface defect density, Nst were
extracted from the characteristics for each of the studied IXZOs. At higher T
the mobility follows the Arrhenius law with an upward distortion, increasing as
T was lowered, gradually transforming into the exp [-(T0/T)1/4] variation. We
showed that mu(T, Nst) follows mu0exp[-Eaeff(T,Nst)/kT], with T-dependent
effective activation energy Eaeff(T, Nst) accounts for the data, revealing a
linear correlation between Eaeff and Nst at higher T. Temperature variation of
Eaeff(T, Nst) was evaluated using a model assuming a random distribution of
conduction mobility edge Ec values in the oxides, stemming from spatial
fluctuations induced by disorder in the interface traps distribution. For a
Gaussian distribution of Ec, the activation energy Eaeff(T, Nst) varies
linearly with 1/T, which accounts satisfactorily for the data obtained on all
the studied IXZOs. The model also shows that Eaeff(T, Nst) is a linear function
of Nst at a fixed T, which explains the exponential decrease of mu with NST.
