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

Abstract 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 Δ μ /Δ T ) plotted as a function of n can be divided into three regions: (1) Region I (3 × 10 18 n 19 cm − 3 ); Δ μ /Δ T > 0 and μ decreasing with increasing n , (2) Region II (4 × 10 19 n 20 cm − 3 ); μ independent of T (Δ μ /Δ T = 0) and (3) Region III ( n > 3 × 10 20 cm − 3 ); Δ μ /Δ T T –ln ( μT ) curves were lower than the thermal energy k B T 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 × 10 18 cm − 3 . The dependence of Δ μ /Δ T 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 .