Carrier Transport through Grain Boundaries in Highly Transparent Conductive Ga-Doped ZnO Films

摘要

Polycrystalline Ga-doped ZnO films (GZO) with different thicknesses ranging from 70 to 500nm were deposited by ion plating with DC arc discharge at a glass substrate temperature of 200℃. The dominant role of grain boundary scattering in carrier transport in the films is demonstrated by varying the film thickness and grain size. With increasing film thickness, the grain size increases and alignment of the c-axis between the columnar grains is improved. A comparison of Hall mobility and optical mobility shows that for GZO films with thicknesses of above 100nm, carrier transport is mainly limited by grain boundary scattering, whereas for GZO films with thicknesses of less than 100nm, both intragrain scattering and grain boundary scattering are the mechanisms limiting carrier transport. By comparing a grain-size-effect theory with the electrical resistivity data, we obtained that grain boundary reflection coefficients deceases with increasing the grain size.