Power-dependent physical properties of $$\mathbf{GaN}$$ thin films deposited on sapphire substrates by RF magnetron sputtering

Abstract

Gallium nitride $$(\hbox {GaN})$$ thin films were grown on the $$\hbox {Al}_{2} \hbox {O}_{3} \left( {0 0 0 1} \right) $$ 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 $$\hbox {GaN}$$ thin film growth and its physical properties. The X-ray diffraction results confirmed that the $$\hbox {GaN}$$ thin film had a polycrystalline structure with planes of $$\left( {101} \right) $$ and $$\left( {202} \right) $$ . The structural parameters of the thin film changed with RF powers. It was also found that the optical band gap energy of $$\hbox {GaN}$$ thin films varied with changing RF power. From the atomic force microscopy images, almost homogeneous, nanostructured and a low-rough surface of the $$\hbox {GaN}$$ thin film can be observed. From scanning electron microscopy analysis, dislocations and agglomerations were observed in some regions of the surface of the $$\hbox {GaN}$$ thin film. $$E_{2}\,({\hbox {high}} )$$ optical phonon mode of $$\hbox {GaN}$$ was observed, proving the hexagonal structure of the thin film. The residual stress in the $$\hbox {GaN}$$ 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 $$\hbox {GaN}$$ 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.