Preparation method of low-granularity and low-dark-spot semi-insulating gallium arsenide wafer

The invention discloses a preparation method of a low-granularity and low-dark-spot semi-insulating gallium arsenide wafer, and belongs to the technical field of preparation of semiconductor substrate materials. The method specifically comprises the following steps: proportioning 7N gallium arsenide polycrystals and semi-insulating gallium arsenide crystal return materials according to a certain proportion, cleaning impurities and attachments on the surfaces of the polycrystals and the return materials by using a corrosive liquid, putting the gallium arsenide polycrystals, the return materials, boron oxide and arsenic into a PBN crucible in a clean room, sleeving a high-purity carbon cap on the neck of the crucible, putting the PBN crucible into a quartz tube, placing a quartz sealing cap at the opening of the quartz tube, heating and vacuumizing the quartz tube, sealing and welding, carrying out single crystal growth by adopting a VGF process, cutting off the head and the tail of the obtained single crystal,