p-Type Nonpolara-ZnO:N Thin Films onr-Sapphire Substrates Grown by Molecular Beam Epitaxy

摘要

We have grown nonpolar nitrogen (N) dopeda-plane zinc oxide (ZnO) films onr-plane sapphire substrates in order to eliminate the self-polarization component in the growth direction, which decreases the doping efficiency of N acceptors. Nonpolara-ZnO:N films were grown by plasma-assisted molecular beam epitaxy (PA-MBE) using Zn metal and a plasma source of O(2)and NO mixed gas. It was confirmed by reflection high-energy electron diffraction and x-ray diffraction that single phasea-plane ZnO:N films were grown on ther-plane sapphire substrates. After the PA-MBE growth, the post-annealing was performed in an oxygen atmosphere. Photoluminescence experiments showed donor-acceptor pair emissions increase with increasing the annealing temperature (<= 700 degrees C). AC magnetic field Hall effect measurements revealed thatn-type conduction of the as-grown films clearly changed to thep-type at the annealing temperature of 650 degrees C. The resistivity, hole concentration, and mobility were rho = 3.4 omega cm,p = 8.0 x 10(17) cm(-3), and mu = 2.3 cm(2)/Vs, respectively.