Preparation method for low-dislocation density Al Ga N epitaxial thin film

The invention discloses a preparation method for a low-dislocation density Al Ga N epitaxial thin film. The preparation method comprises the following steps of: epitaxially growing a AlN thin film on a substrate; epitaxially growing a plurality of periodic Al Ga N/AlN superlattice insertion layers on the prepared AIN thin film; epitaxially growing the Al Ga N thin film on the surface of the above Al Ga N/AlN superlattice insertion layer; corroding to prepare the Al Ga N thin film, and forming the Al Ga N thin film with a dislocation pit; depositing a dielectric film on the surface of the Al Ga N thin film with the dislocation pit, and forming an epitaxial wafer with the dielectric film; polishing the epitaxial wafer with the dielectric film to prepare an epitaxial wafer template; and continuously and epitaxially growing Al Ga N on the epitaxial wafer template to prepare the Al Ga N epitaxial thin film, wherein x and y is positive numbers not more than 1. According to the preparation method, an effect of low dislocation density is achieved.