Improvement of m-plane ZnO films formed on buffer layers on sapphire substrates by mist chemical vapor deposition

The crystal quality of ZnO films grown by mist chemical vapor deposition (mist-CVD) was improved by introducing ZnO buffer layers on sapphire substrates. The ZnO films were grown by high-speed rotation-type mist-CVD with a ZnCl2 aqueous solution, which provided uniform epitaxial layers over 2-inch wafers. To grow the ZnO buffer layers, it is necessary to form small grains of polycrystal. Therefore, we attempted to grow the ZnO buffer layers using a Zn(CH3COO)(2) aqueous solution, which provides a small grain size of about 100nm. By using the buffer layers, the full width at half-maximum of an X-ray -rocking curve for the ZnO film was reduced from 0.69 degrees to 0.38 degrees, showing improvement of the crystal quality.