Electrical transport properties of amorphous Zn-doped In2O3 films in a wide region of carrier density

Abstract

We have systematically investigated the temperature dependence of resistivity p and Hall mobility μ of amorphous Zn-doped In2O3 films (350 nm) in the temperature range 2.0 to 300 K. We prepared film specimens with carrier density n ≈ (2 x 1017 − 6 x 1020/cm3) and p ≈ (3 − 4000)μΩcm (300 K) by changing the gas pressure of oxygen during DC-magnetron sputtering. The μ(n) shows the convex characteristic with a broad peak near n ≈ 3 x 1020cm3, taking the value μ ≊ 50cm2/Vs. In the low n region, it has been found that the μ seems to change as μ ∝ n1/3 . For films with n ≥ 5 x 1019/cm3, the p(T) shows the metallic behavior between ≈ 20 K and 300 K. On the other hand, for films with n ≤ 1019/cm3, p(T) essentially shows the insulating behavior at whole temperatures. From the analysis of the p(T) in the expression of p(T) = p0 exp(A/Tn) at low temperatures, we obtained that the data is well explained by n = 1/2 for dirty films. The estimated electron mean free path ℓ(4 K) deviates from the linear dependence of ℓ ∝ n to decease abruptly near ℓ ≈ 0.2 − 0.4 nm corresponding to the average distance between In and In (or oxygen).