Temperature dependence of electrical properties of Ga-doped ZnO films deposited by ion plating with DC arc discharge

Ga-doped ZnO (GZO) films with carrier concentration n ranging from 3 × 1018 to 1.04 × 1021 cm− 3 were deposited by ion plating with DC arc discharge. The results of Hall effect measurements of the GZO films revealed that the gradients of Hall mobility (μ)-temperature (T) curves (denoted by Δμ/ΔT) plotted as a function of n can be divided into three regions: (1) Region I (3 × 1018 < n < 4 × 1019 cm− 3); Δμ/ΔT > 0 and μ decreasing with increasing n, (2) Region II (4 × 1019 < n < 3 × 1020 cm− 3); μ independent of T (Δμ/ΔT = 0) and (3) Region III (n > 3 × 1020 cm− 3); Δμ/ΔT < 0. For all GZO films, the activation energies extracted from the 1000/T–ln (μT) curves were lower than the thermal energy kBT at 300 K, indicating that the carrier electrons can overcome the potential barriers at grain boundaries. Moreover, comparison of the calculated mean free path l of the carrier electrons and the depletion layer width at the grain boundaries showed that the grain boundary scattering mechanism plays a minor role in the carrier transport compared with the intra-grain scattering mechanism for GZO films with n higher than 3 × 1018 cm− 3. The dependence of Δμ/ΔT on n demonstrates the continuous transformation of the dominant intra-grain scattering mechanism from the ionized impurity scattering mechanism to the phonon scattering mechanism with increasing n.

► Electrical properties of the ion-plating GZO films have been studied.
► The carrier concentration n was in the rang of 3 × 1018 to 1.04 × 1021 cm– 3.
► The grain boundary scattering plays a minor role on the carrier transport.
► The n-Δμ/ΔT plots reflect the dominant scattering mechanism in the intra-grains.