Epitaxial growth of gallium nitride by ion-beam-assisted evaporation

The epitaxial growth of gallium nitride thin film was obtained on the inclined Si(111) substrates by the process of ion-beam-assisted evaporation (IBAE) at the low temperature of 500 °C. The film composition determined by Rutherford backscattering spectrometry shows that the synthesized film is a stoichiometric nitride. The epitaxial quality of GaN film is enhanced by minimizing the bombardment-induced film damage by decreasing the ion flux. However, the crystallinity of the GaN film becomes very poor when the ion flux is not sufficient to densify the film. The optimum flux ratio of N⁺₂ to Ga and the energy of incident N⁺₂ ions for the epitaxial growth were found to be 3.4 and 50 eV, respectively. The GaN film deposited on the 4 °-inclined Si (111) with respect to substrate surface shows much better crystalline quality compared with that on the 0 ° inclined Si(111) due to many stable nucleation sites. A thin amorphous layer exists at the interface between GaN and Si(111) substrate and acts as a buffer zone enabling the subsequent epitaxial growth of GaN by relaxing the large misfit strain (23%) in the early stage of film growth. The epitaxial GaN film shows an orientational relation with the Si(111) substrate.