Hole transport in p-type ZnO films grown by plasma-assisted molecular beam epitaxy

The hole transport properties of nitrogen doped p-type ZnO grown on c-plane sapphire (c-Al2O3) were investigated by temperature-dependent Hall-effect measurements. The experimental Hall mobility was found to be considerably lower than the calculated mobility including ionized impurity scattering, acoustic-mode deformation potential scattering, piezoelectric potential scattering, and polar optical phonon scattering. Atomic force microscopy and x-ray diffraction measurements demonstrated that p-type ZnO on c-Al2O3 consisted of two kinds of 30 degrees-rotated domains surrounded by grain boundaries. Thus, taking the effect of inhomogeneous microstructure on the mobility into account, the calculated mobility agreed favorably with the experimental data. This agreement indicates that besides ionized impurity and acoustic deformation potential scattering at low temperatures and the polar optical phonon scattering at high temperatures, the effects of the inhomogeneous microstructure in p-type ZnO films play a more important role in determining the hole mobility. (c) 2006 American Institute of Physics.