Effects of post-annealing on GaN thin films growth using RF magnetron sputtering

Radio-frequency (RF) magnetron sputtering is one of the methods to deposit thin films that have been widely used in the deposition of GaN thin films to fabricate optoelectronic devices. However, the crystallisation of the GaN films deposited using RF magnetron sputtering at room temperature shows GaN amorphous structure. Therefore, post-annealed method at temperature 950 degrees C in N-2 condition using CVD furnace is applied after GaN thin film was deposited on Si (111) with and without AlN buffer layer by RF magnetron sputtering at room temperature. Here we report the discovery and characterisation of the GaN thin films after post-annealing at 950 degrees C in nitrogen ambient with and without AlN as a buffer layer. X-ray diffraction (XRD) is used to identify the crystal phase of GaN thin films. The surface morphology including thickness, surface roughness and grain size is studied by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The analyses of XRD show the amorphous structure for the GaN thin films with and without AlN buffer layer that does not undergo post-annealing. After undergoing post-annealing, it does not show any crystalline structure of GaN but crystalline structure of gallium oxide (Ga2O3) dominantly exists in the GaN thin film without AlN buffer layer. AFM analysis shows the grain size and the surface roughness for GaN thin film without AlN buffer layer increases after annealing which are 50.15 nm and 0.87 nm compared with before annealing which are 43.42 nm and 0.61 nm respectively. However, the grain size and surface roughness for GaN films without buffer layer are lower compared with GaN films with the AlN buffer layer even after post-annealing process which are 98.13 nm and 1.30 nm, respectively.