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

摘要

Ga-doped ZnO (GZO) films with carrier concentration n ranging from 3×10~(18) to 1.04×10~(21) 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 (3×10~(18)0 and μ decreasing with increasing n, (2) Region Ⅱ (4× 10~(19)3×10~(20)cm~(-3)); Δμ/ΔT<0. For all GZO films, the activation energies extracted from the 1000/T-In (μT) curves were lower than the thermal energy k_BT at 300 K, indicating that the carrier electrons can overcome the potential barriers at grain boundaries. Moreover, comparison of the calculated mean free path I 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 3×10~(18) 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.