High purity gallium for producing compound semiconductor, refining process and apparatus for the same

In a high purity raw Ga material for use in the preparation of a compound semiconductor, a raw Ga material used for preparing a compound semiconductor which has a difference ΔC=|ΣAn−ΣBn| of 5 ppm by atomic or lower when subjected to a “test method for impurity-concentrated Ga” as defined below, where ΣAn represents the total quantity of the components contained in the sample of an impurity-concentrated Ga, which is at least one element of group A components selected from the group consisting of B, Na, Mg, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Au, Hg, Pb, and Bi;

• and ΣBn represents the total quantity of the components contained in the sample of impurity-concentrated Ga, which is at least one element of group B components selected from the group consisting of F, Si, S, Cl, Ge, Se, Sn, and Te.
• “Test method for impurity-concentrated Ga” is defined as a test method comprising:
• using an apparatus for refining gallium comprising a vessel, having a cylindrical inner wall made of a 3 mm thick SUS304 steel sheet provided with a 0.3 mm thick fluororesin coated inner wall plane, said vessel having an inner radius of 60 mm and a height of 40 mm, a cooling zone attached to the outer peripheral plane of said vessel, a suction pipe installed at the central portion of said vessel, and a magnetic rotator provided to the lower portion of said vessel;
• filling said vessel with a raw Ga material in liquid state at a quantity as such that it amounts to 30 mm in height inside the vessel while purging the space inside the vessel with an inert gas;
• and
• obtaining a sample of impurity-concentrated Ga as follows:
• while applying a circular flow of 100±10 rpm to the liquid raw Ga material by using the rotator, maintaining the liquid raw Ga material at a temperature of 29.6±0.5° C., and passing a cooling water at a temperature of 5° C. through the cooling zone, thereby allowing progressive solidification of the liquid to proceed from the inner wall of the vessel towards the central portion of the vessel at a solidification rate as such that the entire liquid may solidify in 60±5 minutes, then sampling the liquid phase through the suction pipe when the radius of the remaining liquid phase becomes 20 mm.