Optimization study of metal-organic chemical vapor deposition of ZnO on sapphire substrate

Metal-organic chemical vapor deposition (MOCVD) of ZnO with dimethylzinc (DMZn) and tert-butanol (t-BuOH) as Zn and oxygen precursors has been investigated and optimized in this work. Growth experiments show hydrogen addition, usually used to suppress carbon incorporation, should be kept at a low concentration due to its strong etching effect on ZnO. We found that reduction of hydrogen concentration also results in smoother films. Growth at a reactor pressure of 4-8 kPa resulted in smoother films as compared to growth at 2 kPa, and growth temperature of 470°C is also observed to result in smoother films, while fully suppressing gas phase pre-reactions. A low growth rate also helps to obtain smooth surface morphology, which is helpful to achieve improved crystal quality of the subsequent high temperature epilayer. The optimized growth parameters provided by this work are helpful for achieving high quality ZnO epilayer growth on sapphire substrates.