The motive of the work was to study the different aspect of synthesis of GaN with different routes and modify the structural, optical, electrical and magnetic properties. GaN thin films of high epitaxial quality were deposited with ion beam assisted molecular beam epitaxy technique.As-deposited GaN films were implanted with 180 keV Co ions at different fluences. The structural properties were investigated with high resolution X-ray diffraction as well as with RBS/C technique. SQUID measurements were performed to study the magnetic properties of the implanted and annealed samples with RTA at 1150 C for 20 s. The ferromagnetic hysteresis loop was observed. Both the field cooled and zero field cooled curve intersect at the temperature of 350 K, which implies that the magnetic ordering persists even at the temperature higher than the room temperature.For the application point of view, Au/n-GaN Schottky diodes were fabricated and in-situ current-voltage measurements were performed during ion irradiation.To summarise, different ion beams in different energy regime were used to synthesize GaN films as well as modifying the properties of GaN in a controlled way.