Smooth surface, low electron concentration, and high mobility ZnO films on c-plane sapphire

ZnO thin films were grown on c-plane sapphire substrate using plasma-assisted molecular beam epitaxy. The thickness of MgO buffer layers was optimized for structural and electrical properties of the epi-ZnO films. It is found that with MgO buffer growth time of 60 s, the epi-ZnO film exhibited narrow X-ray diffraction peak as well as low surface roughness. In the meantime, the electron concentration reached a minimum of 2.03×1016/cm3 and high mobility of 169.4 cm2/V S. These results demonstrate a route to grow good crystals together with excellent mobility and low residual electron concentration, which can ultimately satisfy the requirement for acceptor doping as well as device engineering.

► MBE growth of high quality 2-dimensional ZnO films on c-sapphire.
► Effect of MgO buffer layer on crystallinity, surface morphology, and electrical properties is comprehensively studied.
► ZnO structural properties are optimized.
► Electrical properties also show excellent results.