Power-dependent physical properties of GaN thin films deposited on sapphire substrates by RF magnetron sputtering

Gallium nitride (GaN) thin films were grown on the Al2O3 (0001) substrate using radio frequency (RF) magnetron sputtering under various RF powers. Many experimental techniques were used for investigating the effects of RF power on the GaN thin film growth and its physical properties. The X-ray diffraction results confirmed that the GaN thin film had a polycrystalline structure with planes of (101) and (202). The structural parameters of the thin film changed with RF powers. It was also found that the optical band gap energy of GaN thin films varied with changing RF power. From the atomic force microscopy images, almost homogeneous, nanostructured and a low-rough surface of the GaN thin film can be observed. From scanning electron microscopy analysis, dislocations and agglomerations were observed in some regions of the surface of the GaN thin film. E2 (high) optical phonon mode of GaN was observed, proving the hexagonal structure of the thin film. The residual stress in the GaN thin films was calculated from Raman measurements. Furthermore, an agreement between the experimental measurements was also examined. The morphological, structural and optical properties of the GaN thin film could be improved with altering RF power. These films could be used in devices such as light emitting diodes, solar cells and diode applications.