GaN film growth on LiNbO₃ surfaces using molecular beam epitaxy

GaN has been used for high power, high frequency electronic and optoelectronic devices such as light emitting diodes and laser diodes. Most of the GaN films grow on sapphire (0001) and silicon (111) substrates. In these work, we are trying to grow GaN films on lithium niobate (LiNbO₃) substrates using molecular beam epitaxy (MBE). As a ferroelectric materials, LiNbO₃ has a spontaneous polarization which may provide excellent control of polarity of GaN. The growth of GaN films on LiNbO₃ has been performed after the LiNbO₃ substrates was annealed in air at 1000°C for 2 hours. The annealed substrates allowed us to prepare atomically flat surfaces and improve adhesion of GaN on LiNbO₃. The AlN buffer layer was deposited to get a smaller lattice mismatch with the GaN films. Compared with GaN films grown without a AlN layer, the crystal qualities of GaN films with AlN buffer layers are extremely improved. The surface morphology of LiNbO₃ substrates and the grown GaN films were characterized by atomic force microscopy (AFM), and the crystal structures were studied by X-ray diffraction (XRD).