Non-Arrhenius conduction due to the interface-trap-induced disorder in X-doped amorphous InXZnO thin-film transistors

TL;DR

This study investigates how interface trap-induced disorder affects conduction in In-X-Zn oxide thin-film transistors, revealing a non-Arrhenius temperature dependence modeled by a Gaussian distribution of conduction edge energies.

Contribution

It introduces a model linking interface trap disorder to non-Arrhenius conduction behavior, supported by experimental data on various doped amorphous oxide transistors.

Findings

Mobility follows a distorted Arrhenius law transitioning to a T^{-1/4} dependence.

Effective activation energy correlates linearly with interface defect density.

A Gaussian distribution model explains the temperature dependence of activation energy.

Abstract

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.