Roles of Si Irradiation during the Growth Interruption on GaN Film Qualities in Plasma-Assisted Molecular Beam Epitaxy

Roles of Si irradiation during GaN growth interruption in plasma-assisted molecular beam epitaxy are studied. It is found that irradiated Si can modulate the GaN surface energy to enhance the Ga surface diffusion, resulting in a flat GaN surface with monolayer steps as determined by atomic force microscopy observations. Furthermore, cross-sectional transmission electron microscopy reveals that threading dislocations in a GaN film can be greatly reduced by Si irradiation, which agrees very well with the results of high-resolution X-ray diffraction measurement of asymmetric (102) GaN diffraction. These two positive effects of Si irradiation are promising for growing high-quality GaN with excellent surface morphology and low dislocation density for device applications.