Abstract
We demonstrate the successful growth of GaN columnar and microdisk structures on a (111) Ge/Si substrate via metal organic chemical vapor deposition. X-ray diffraction and energy disperse spectroscopy results reveal that the well aligned GaN nanocolumnar structures are grown on a Si substrate by using the Ge layer. The relatively higher growth temperature induces a change in surface morphology of GaN from columnar to microdisk structures. The possible growth mechanism of columnar structured GaN was considered from the Ga-metal/Ge eutectic materials system.