With a wide bandgap of 3.370 eV and a large exciton binding energy of 60 meV at room temperature

ZnO has attracted considerable attention as a promising material for optoelectronic devices

especially in short-wavelength light emitting diodes (LEDs) and laser diodes. However

the lack of high-quality p-type ZnO has hampered the development of ZnO homostructural LEDs. The reported p-type ZnO films always have very low Hall mobility at room temperature (1~10 cm

2

·V-1·s

-1

). For improving the quality of p-type ZnO

it is very important to understand the hole scattering mechanisms in these films.In this paper

nitrogen-doped p-type ZnO films were grown on sapphire substrate by plasma-assisted molecular beam epitaxy

using radical NO as oxygen source and nitrogen dopant. The electrical properties of p-type ZnO films were investigated by temperature-dependent Hall-effect (T-Hall) measurements. The activation energy of N acceptor was deduced to be 75 meV by fitting the T-Hall data. The hole scattering mechanisms were studied both experimentally and theoretically. The experimental Hall mobility was found to be considerably lower than the calculated mobility including ionized impurity scattering

acousti

c

-mode deformation potential scattering

piezoelectric potential scattering

and polar optical phonon scattering. However

taking the effect of inhomogeneity on the mobility into account

the calculated mobility was in excellent agreement with the experimental data. This 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.