A method of forming a multijunction solar cell comprising at least a first subcell and a second subcell, the method including forming a first alpha layer over said first solar subcell using a surfactant and dopant including selenium or tellurium, the first alpha layer configured to prevent threading dislocations from propagating; forming a metamorphic grading interlayer over and directly adjacent to said first alpha layer; forming a second alpha layer using a surfactant and dopant including selenium or tellurium over and directly adjacent to said grading interlayer to prevent threading dislocations from propagating; and forming the second solar subcell over said grading interlayer such that the second solar subcell is lattice mismatched with respect to the first solar subcell.