Longitudinal and Hall Transport in Amorphous InGaZnO₄ Films Prepared by rf Sputtering Method

Abstract

We systematically investigated the temperature behaviors of the electrical conductivity and Hall coefficient of two series of amorphous indium gallium zinc oxides (a‐IGZO) films prepared by rf sputtering method. The two series of films are ∼700 and ∼25 nm thick, respectively. For each film, the conductivity increases with decreasing temperature from 300 K down to Tmax, where Tmax, ranging from ∼90 to ∼115 K for our films, is the temperature at which the conductivity reaches its maximum. Below Tmax, the conductivity decreases with decreasing temperature. Both the conductivity and Hall coefficient vary linearly with lnT at low temperature regime. The lnT behaviors of conductivity and Hall coefficient cannot be explained by the traditional electron–electron interaction theory, but can be quantitatively described by the current electron‐electron theory due to the presence of granularity. Combining with the scanning electron microscopy images of the films, we propose that the boundaries between the neighboring a‐IGZO particles could make the film inhomogeneous and play an important role in the electron transport processes.

Electron effective mass and electronic structure in nonstoichiometric amorphous Indium Gallium Zinc Oxide films

“…These features mean films No.2 to No.4 all possess degenerate semiconductor (or metal) characteristics in electrical transport properties. The enhancement of resistivity with decreasing temperature below ∼150 K originates from weak localization effect [18][19][20] and electron-electron interaction effect [20][21][22][23][24][25], while the reduction of carrier concentration is also caused by the electron-electron interaction effect [24][25][26][27]. According to Möbius [28,29], the logarithmic derivative of the conductivity w = d ln σ/d ln T is more sensitive than the TCR and defines a more accurate and reliable criterion to distinguish between metallic and insulating behaviors.…”