Effects of nitridation durations on the synthesis of wurtzite GaN thin films by spin coating method

In this paper, the effects of nitridation durations on the structural, surface morphologies and lattice vibrational properties of gallium nitride (GaN) thin films grown via spin coating method were reported. X-ray diffraction (XRD) results revealed that all the deposited GaN thin films have wurtzite structure and with GaN(002) preferred orientation. In addition, the crystallinity of the GaN thin films increases with increasing of nitridation durations from 15 to 75 min while it degrades at 105 min. Field-emission scanning electron microscopy observations showed that GaN thin films with hexagon grains were formed at nitridation duration of 45 and 75 min, whereas rose-like microstructures were formed at nitridation duration of 105 min. P-polarized infrared reflectance measurements demonstrated that the reststrahlen feature of GaN thin films gradually increases from 15 to 75 min and diminished at 105 min, which is consistent with the XRD results. Finally, all the results revealed that the duration of 75 min was the most efficient time for the nitridation process.