Origin of definite Hall voltage and positive slope in mobility-donor density relation in disordered oxide semiconductors

Amorphous oxide semiconductors (AOSs) are expected for alternative channel materials in thin-film transistors owing to their large electron mobilities. While, it is known that AOSs exhibit peculiar electron transport properties. Definite Hall voltages are observed even for mobilities < 0.2 cm(2)/V s, which correspond to a very short mean free path (MFP) of 0.008 nm. Furthermore, Hall mobility increases with increasing the donor density. This paper reports that a percolation conduction model explains them; quantitative analyses based on the Boltzmann's transport theory prove that carriers within the potential barriers have large MFPs of 0.5-1 nm. The percolation model also explains variable-range-hoppinglike and weak-localizationlike behaviors.