The effects of buffer growth parameters on heteroepitaxial ZnO films grown by pulsed laser deposition

The effects of buffer layer deposition conditions on subsequent ZnO epitaxy on sapphire (0001) were examined. An initial ZnO buffer layer improves surface roughness for a wide range of buffer layer growth temperatures and pressures. Changes in buffer layer growth pressure and temperature have a moderate effect on the roughness of subsequent film growth. However, the conditions for buffer layer deposition have a large impact on crystallinity of subsequent films. In particular, the out-of-plane X-ray diffraction rocking curve full-width half-maximum decreased as buffer deposition temperature or O2/O3 pressure increases. Carrier mobility in the subsequent thick ZnO film was enhanced with increase in buffer layer deposition temperature. Carrier concentration decreased with increasing buffer layer deposition pressure.